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Acta Psychologica 73 (1990) 115-129 North-Holland
COMPONENTS OF STROOP-LIKE IN WORD READING * Wido LA HEIJ,
Bart HAPPEL
INTERFERENCE
and Marcel MULDER
Unruersrty of L.erden, The Netherlan& Accepted June 1989
Previous research has shown that the naming of the picture of, for example, a guitar is substantially delayed when tt is accompamed by the name of an obJect from the same semantic category (e g , PIANO) as compared to a nonword control (e.g , xxxxx) La HeiJ (1988a) has shown that a large part of this Stroop-hke mterference effect can be attnbuted to two semantic characteristics of the distractor word: tts semantic stmilarity to the target picture and tts semantic relevance m the task at hand. Furthermore, tt was argued that the locus of these two interference effects is the process of target-name retneval. If this ts true, semanttc interference effects should dimuush or disappear when, Instead of a ptcture-naming task, a word-reading task is used In the present study thts predictton ts tested The effects of four distractor charactensttcs are exammed semantic relatedness, semanttc relevance, response set membershtp and wordness In contrast to the ongmal picture-nammg task only the effect of wordness reached sigmftcance. The results of experiments 2 and 3 show that the absence of sigmftcant semantic context effects m experiment 1 1s not simply due to the fact that a distractor word has less time to affect a word-reading response. The results are taken to support a name-retneval account of semanttc interference m color and picture nammg
Introduction In the original Stroop task, subjects are required to name the color of color patches and of incongruently colored color words (e.g., the word RED printed in green ink). Compared to the naming of color patches, the latter situation results in a remarkable increase in naming latency. Ever since the introduction of this task in psychology (Stroop 19354 attempts have been made to determine the locus or loci of this interference effect. Recently, Stroop interference has mainly been attributed to a rather peripheral process of response competition and/or * Requests for reprints should be sent to W. La HetJ. Faculty of Social Sciences, Umt of Expenmental and Theoretical Psychology, University of Letden, P 0 Box 9555, 2300 RB Leaden, The Netherlands OOOl-6918/90/$3.50 0 1990, Elsevier Sctence Publishers B.V (North-Holland)
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to interference m a semantic decision stage (see, e.g., W.R. Glaser and Diingelhoff 1984; Lupker and Katz 1981; Rayner and Springer 1986; Seymour 1977). Information concerning the locus or loci of Stroop interference can be derived from studies in which attempts were made to determine which dtstractor characteristics affect the amount of interference. Klein (1964; see also Fox et al. 1971) showed that, as compared to nonsense syllables, the following sets of distractor words induced an increasing amount of interference on color nammg: (a) rare English words (e.g., SOL), (b) common English words (e.g., PUT), (c) incongruent color-related words (e.g., LEMON in red ink), (d) color words that did not name one of the target colors in the experiment (e.g., TAN in red ink), and (e) incongruent color words that did name one of the target colors m the experiment (e.g., GREEN in red ink). The increase in interference from condition (a) to (e) is referred to as the ‘semantic gradient’. Klein’s results have often been interpreted to indicate that the amount of interference increases with the strength of the semantic relation between the word and the accompanying color. Neumann (1980), however, pointed out that the effect of a semantic relation between distractor and target cannot be determined in the original Stroop task, due to its confounding with other distractor characteristics. For example, in Klein’s (1964) experiment the distractor word GREEN not only differs from the distractor word PUT in the fact that the word GREEN is semantically related to the accompanymg color (e.g., red), but also in two other respects. First, the word GREEN is a member of the small set of response alternatives in the experiment (a characteristic that will be referred to as response set membershzp). Second, the word GREEN is highly relevant in a task m which colors have to be named (a characteristic that will be referred to as semantic relevance). In a picture-word variant of the Stroop task, using an experimental design developed by Neumann (1980), La HeiJ (1988a) disconfounded the effects of semantic similarity, semantic relevance, response set membership, and ‘wordness’ (the distractor being a word or a series of Xs). The results showed that all of these distractor characteristics attributed significantly to the overall Stroop interference effect. An important finding was that the interference effect due to a semantic relation between distractor and target was very small as compared to the combined effects of semantic relevance, response set membership and wordness. On average, only 13% of the overall interference effect could be attributed to this factor.
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La Heij (1988a) argued that this finding indicates that a large part of the overall Stroop interference effect is not due to a semantic relation between distractor and target, and cannot - for that reason - be attributed to the extra time needed to resolve a ‘semantic ambiguity’, as suggested in the semantic-decision account of Stroop interference. Moreover, it was argued that even the effect of semantic similarity might not be due to interference m a semantic-decision stage. This conclusion was based on two findings in the literature. First, a substantial number of studies have shown that Stroop interference can be eliminated when, instead of verbal naming responses, non-naming responses like button pressing or manual sorting are required. 1 This result suggests that Stroop interference has to do wtth the retrieval and/or production of a verbal naming response. Second, Rayner and Springer (1986) have shown that semantic interference effects in a picture-word interference task disappear when the drstractor word 1s graphemically similar to the prcture’s name, a characteristic of the distractor that is supposed to facilitate the process of name retrieval (see, e.g., Lupker 1982). As an alternative, it was suggested that the effects of semantic similarity and semantic relevance are localized at the level of targetname retrieval (see also La Heij 1988b; W.R. Glaser and Glaser 1989). Within the framework of recent models of picture processing (e.g. W.R. Glaser and Glaser 1989; Warren and Morton 1982; Humphreys et al. 1988) interference in name-retrieval may be thought of as the result of inhibitory interactions within the lexicon: the activation of the phonological representation of the context word inhibits or temporarily ‘blocks’ the activation of the phonological representation of the picture’s name. The fact that a word that is categorically related to the target picture induces more interference than an unrelated word could then be attributed to ‘reverse priming’ (Neumann 1986): the semantic representation of the picture mcreases the activation level of the phonological representation of the context word, either due to a spread ’ Stroop Interference was ehmmated by usmg non-verbal or non-nammg responses m the studies of, for example, Egeth et al. (1969), Flowers and Dutch (1976), and VNZJ and Egeth (1985) In a number of other studies, however, this marupulatlon reduced but not completely ehmmated Stroop mterference (e g., Hock and Egeth 1970, Keele 1972, Prltchatt 1968, see also Stwhng 1979). A plausible explanation for most of these residual Stroop Interference effects IS that subjects used covert nammg responses The reader IS referred to Dalrymple-Alford and Azkoul (1972) and La HeI] (19881, 141-152) for a dIscussIon of this Issue
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of activation within a semantic system (as assumed in the model of W.R. Glaser and Glaser (1989)) or due to the fact that m the process of picture-name retrieval a number of categorically related words get activated, including the one that is already activated by the context word. In the present study we will examine a prediction that can be derived from this name-retrieval account. In most models of picture and word processing (e.g., W.R. Glaser and Glaser 1989; Seymour 1973; Van der Heijden 1981; Warren and Morton 1982), it is assumed that an important difference between the reading of words and the naming of pictures is the ease with which phonological representations are activated. In discussing the two general processing stages that are involved in picture naming - picture identification and name retrieval - McCauley et al. (1980) for instance, noted: ‘the first stage, in which contact is made with semantic memory, seems to be automatic, but the second stage appears to require an investment of attention to consult the internal lexicon for a name. This stands m marked contrast to evidence that when stimuli are words, their stored phonetic codes.. . as well as their stored semantic codes _. . can be activated automatically’ (1980: 274). Hence, if the distractor characteristics semantic relatedness and semantic relevance interfere in the process of picture-name retrieval, the prediction can be derived that these effects will diminish or even disappear when instead of a picture-naming task, a word-reading task is used. A task that is relevant for evaluating this prediction is the word-word variant of the Stroop task; a task in which two color words are presented, one of which has to be read aloud (M.O. Glaser and Glaser 1982; Van der Heijden 1981). At first sight the results of these studies do not seem in accordance with the above prediction: despite the fact that subjects were asked to read a color word instead of naming a color, incongruent distractor words induced a full-blown Stroop interference effect. The similarity between the color-word and word-word variant of the Stroop task made M.O. Glaser and Glaser hypothesize that ‘the same cognitive process underlies word-word.. . and wordcolor conflicts (color component relevant)’ (1982: 888). It should be noted, however, that Van der Heijden (1981) and M.O. Glaser and Glaser (1982) used only three distractor conditions: incongruent (e.g., RED-GREEN), control (e.g., XXX-GREEN), and congruent (e.g., GREEN-GREEN). The finding that the word RED hampers the reading of the target word GREEN as compared to a string of Xs does
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not imply that the interference is semantically based. This issue was recently examined by W.R. Glaser and Glaser (1989). These authors investigated whether an important characteristic of Stroop interference _ Klein’s (1964) semantic gradient - also shows up in a word-word variant of the Stroop task. Their main finding was summarized as follows: ‘the surprising result was that the semantic gradient showed up with only residual values of less then 10 ms. That means that the pairing conditions of distractor and target that provide gradually different inhibitions in the naming task were essentially ineffective in the reading task with word distracters’ (1989: 40). Of most interest is their finding that in a word-reading task the presence of a semantic relation between a distractor word and a target word does not affect response latencies. As argued above, this result is in accordance with a name-retrieval account of semantic interference in picture and color naming. Unfortunately, m the experiments reported by W.R. Glaser and Glaser (1989) a number of distractor characteristics remain confounded. Most importantly, in none of their experiments the effect of the semantic relevance of a distractor word can be assessed. Therefore, in experiment 1, we examine the effects of the distractor characteristics semantic relatedness, semantic relevance, response set membership, and wordness in a word-reading task. In experiments 2 and 3 a possible explanation for the lack of significant semantic interference effects in experiment 1 is evaluated.
Experiment 1 Thts expenment 1s very sumlar to one of the picture-word interference expenments reported by La Hen (1988a) The only important difference is that the target ptctures were replaced by the correspondmg words. SIX target words were selected from two semantic categories: frutts and parts of the body. The followmg dtstractor condtttons were used (see also table 1) (1) related/response set (REL/RS) the dtstractor word 1s related to the target word and 1s part of the response set (e.g., CHERRY (dlStGiCtOr)-PEAR (target)); (2) related/not m response set (REL/NRS): the dtstractor word IS related to the target word but 1s not part of the response set (e.g , GRAPE-PEAR); (3) unrelated/ response set (UNR/RS) the dtstractor word IS unrelated to the target word and IS part of the response set (e.g., NOSE-PEAR), (4) unrelated/not m response set (UNR/NRS). the dtstractor word IS unrelated to the target word and not part of the response set (e.g., HAND-PEAR); (5) irrelevant (IRR): the dtstractor word 1s not a member of the two
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Table 1 Examples of the SIX target-dlstractor combmatlons used m expenment 1 and then charactenstlcs The presence (+) or absence (- ) of the correspondmg charactenstlc IS mdlcated Target
PEAR
DIstractor
BANANA
MOUTH
LEMON
HAND
DOOR
+
_
+
-
_
SemantIcally related to the target word Part of the response set Member of a relevant semantic category a
+
+
-
-
_
+
+
+
+
_
Condltlon
REL/RS
UNR/RS
REL/NRS
UNR/NRS
IRR
label
a The relevant
relevant
semantic
semantic
categones
categones
XXXXX
CONTR
were frmts and parts of the body
frutts
and
body
parts
but
IS a
member
of
a
thtrd,
(6) control (CONTR). the distractor is a senes of five Xs. These SIX distractor conditions allow the exammatton of four kmds of context effects. semantic relatedness (the difference between the REL and UNR conditions), semantic relevance (the difference between the UNR/NRS and IRR conditions), response set membership (the difference between the RS and NRS conditions), and wordness (the difference between the IRR and CONTR conditions) Except for the use of target words instead of target pictures, the stimulus material 1s identical to part of the stimulus matenal used by La Hei1 (1988a: experiment 2, set 2). The data obtained with the correspondmg pictures and distractor words m that study were clear. separate analyses of variance and a Newman-Keuls test showed that all four context effects reached significance. For ease of companson, the results of this picture nammg task are shown m the top row of table 3. Irrelevant,
category
(e.g.,
DOOR-PEAR);
Method
subjects Sixteen students of the University of Leaden served as paid subjects. All had normal or corrected-to-normal vision.
Matertals The Enghsh translattons of the dtstractor-target pairs are shown m table 2. The dtstractor word was always presented at the point of fixation. The target word could appear either above or below the distractor. Distance between the nearest contours of the words was 0.26 degree of visual angle The length of the words ranged from 0.80 degree of visual angle (three-letter word) to 1 86 degree of visual angle (seven-letter word). Viewing distance was 60 cm.
W L.u Her/ et al / Stroop-lake rnterference MIword readrng Table 2 The target-dlstractor and 3 Target
PEAR
CHERRY
BANANA
FINGER
NOSE
MOUTH
DIstractor
combmatlons
used m the vartous
dlstractor
condltlons
121
of experiments
1, 2,
condltlon
REL/RS
UNR/RS
REL/NRS
UNR/NRS
IRR
CONTR
CHERRY
NOSE
GRAPE
EAR
DOOR
XxXxX
BANANA
MOUTH
LEMON
HAND
LOFT
xXxXx
PEAR
FINGER
APPLE
FOOT
WINDOW
xXxXx
BANANA
MOUTH
LEMON
HAND
LOFT
XxXxX
PEAR
FINGER
APPLE
FOOT
WINDOW
xXxXx
CHERRY
NOSE
GRAPE
EAR
DOOR
xXxXx
NOSE
CHERRY
EAR
GRAPE
DOOR
xxxxx
MOUTH
BANANA
HAND
LEMON
LOFT
XXXXX
FINGER
PEAR
FOOT
APPLE
WINDOW
XXXXX
MOUTH
BANANA
HAND
LEMON
LOFT
XxXxX
FINGER
PEAR
FOOT
APPLE
WlNDOW
xxxxx
NOSE
CHERRY
EAR
GRAPE
DOOR
XXXXX
Apparatus
The stimuli were presented on a fast display screen (GT40). Verbal reading latencies were measured by means of a voice key with an accuracy of 1 msec. Presentation and regrstratton of reaction times and errors was controlled by a PDP 11/40 computer
Procedure
Subjects were run mdtvtdually m a dimly lllummated room. At the start of the session they were informed about the SIX words that would serve as targets m the experiment. They were acquainted with the task m a senes of 25 practice trials. Each trial mvolved the following sequence. a dtm flxatton point (asterisk) appeared between two bars m the center of the screen. After pressing a button and an interval of 500 msec, the dtstractor appeared at the pomt of ftxatron and the target word appeared either above or below the distractor. Dtstractor and target remained on the screen for 150 msec. The subJects were told to ignore the dtstractor and to name the word that appeared above or below the dtstractor as fast as posstble whtle retaining accuracy. After each tnal the experimenter entered a code mto the computer to indicate whether the response was correct or false. A distinction was made between incorrect responses (wrong name, the mltratton of a wrong name, or a hesttatron sound like ‘eh’) and cases m whtch the voice key dtd not tngger or triggered too early. A session Involved two blocks of 144 trials (6 target words x 6 dtstractor condtttons x 2 drstractor words per condttron X 2 postttons X 2 rephcatlons). The sttmuh were presented m random order with the restrtctton that a target word was never presented twice m succession. In order to reduce the vanance m the data each block was preceded by four warming-up tnals and each incorrect response was followed by a filler trial. The results of the warming-up and filler tnals were not included m the analyses.
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Table 3 Mean RTs (msec) and error percentages (m parentheses) m the various picture-nammg task reported m La HelJ (1988a) and of the three reported m the present study
dlstractor condltlons of the word readmg expenments
REL/RS
UNR/RS
REL/NRS
UNR/NRS
IRR
CONTR
La HeiJ (1988a) picture
nammg
660 (3 6)
646 (2 5)
649 (1 4)
631 (2 0)
618 (1 0)
600 (1 8)
Expenment Expenment Expenment
1 2 3
584 (0 1) 652 (5 6) 544 (2 3)
576 (0 0) 644 (4 8) 546 (1 4)
584 (0.2) 648 (4.8) 542 (0 6)
574 (0 1) 647 (4 4) 540 (0 3)
583 (0 2) 650 (4 8) 542 (0.4)
541 (0 0) 635 (5 2) 542 (0 0)
Results The raw data were treated as follows: first, RTs of Incorrect reactions and RTs longer than 1000 msec were excluded Next, for each subject, means and standard deviations were calculated for each of the SIX distractor conditions. RTs that deviated more than three standard deviations from their cell mean were excluded. The remaining RTs were used m the calculation of the means. The 1000 msec criterion, the 3-SD criterion, and the trials in which the voice key failed to trigger or triggered too early accounted for 0.8%, 1 l%, and 0.7% of the data, respectively. Table 3 shows the mean RTs and percentages of errors m the six distractor conditions An overall analysis of vanance was conducted on the mean RTs with distractor conditions as within-subjects factor. This factor reached sigmficance (F(5,75) = 19.9; p < 0.001). In a subsequent Duncan post-hoc test, only the differences between the CONTR condition and the five other distractor conditions reached significance at the 0.05 level A separate analysis of vanance over the data of the distractor condrtions REL/RS, UNR/RS, REL/NRS and UNR/NRS, with response set membership and semantic relation as within-subjects factors showed no significant effects. The factor semantic sm-ulanty only approached sigmficance (F(1,15) = 4.5; p < 0 06) (mean RTs were 584 msec and 575 msec m the REL and UNR conditions, respectively). As can be seen m table 3, very few errors were made. Dmx.wton
The SIX distractor conditions used m this sxpenment allow the exammation of the effects of four distractor charactenstics. semantic relatedness (REL-UNR), semantic relevance (UNR/NRS-IRR), response set membership (RS-NRS), and wordness (IRR-CONTR). Of these effects, only the last one reached sigmficance. This fmdmg stands m marked contrast to the results obtained m the correspondmg picture-nammg task of La Heij (1988a), in which all four distractor characteristics induced significant interference effects. So, by changmg the task from picture nammg to word reading, (a)
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the effect of semantic similarity decreased and failed to reach sigmftcance m the analysis of vanance, a fmdmg that 1s m accordance wtth the result of W.R. Glaser and Glaser (1989: experiment 6), (b) the effect of semantic relevance reversed m dtrection, but also faded to reach stgmftcance, and (c) the effect of response set membership disappeared. Underwood and Bnggs (1984. experiment 2) also presented a target word and a dtstractor word stmultaneously, one at the left and one at the right of a central ftxation point. The sublects were mstructed to read the word that appeared m a rectangular box The distractor word was (a) semantically associated to the target (e g., LOAFBREAD), (b) graphemically similar to the target (e.g, BEAD-BREAD), (c) phonemically stmtlar to the target (e.g., FLED-BREAD), (d) unrelated to the target (e g., RISK-BREAD), or (e) a nonword (e.g., HBTM-BREAD) Adult readers showed no stgmftcant differences between these five distractor condtttons. A group of sublects referred to as ‘young poor readers’ (aged between 9 and 12 years old), however, showed a substantial semantic interference effect. That ts, dtstractor words that were semantically associated to the target induced interference as compared to unrelated dtstractor words. In discussmg this fmdmg, Underwood and Bnggs (1984) noted: ‘the poor readers show semantic interference m the word-nammg task, it 1s suggested, because their slow articulatory planning allows ttme for the identiftcation of the meaning of the distractor Readers of greater skill are not vulnerable to interference because they can identify and name the target word either before the semantic processmg of the dtstractor 1s complete, or by bypassing the lextcal route altogether’ (1984: 252) (see also Huttenlocher and Kubicek 1983; West and Stanovich 1982). The difference between the context effects observed m the picture-nammg task of La Heil (1988a) and the present word-reading task may be explained m a stmtlar way. That ts, the absence of sigmftcant semantic context effects m the present experiment may be due to the fact that m a word-reading task less ttme 1s available for the semantic processmg of the dtstractor word (the overall mean word-reading latency m the present expenment was 60 msec smaller than the correspondmg mean picture-nammg latency; see table 3). Thts hypothesis will be exarmned in the next two expenments.
Experiment 2 Two mampulattons can be thought of to ensure that the semantic processmg of the distractor word is completed before a response is nnttated m our present word-reading task. First, the legibthty of the target word can be reduced, resultmg m longer reading latenctes. Second, the distractor word can be presented m advance of the target. In the present expenment we will examme the effect of the first mampulation. Target degradation was achieved by supertmposmg a gratmg of whtte dots on the target (see Meyer et al. (1975) for a sumlar procedure). Method SubJects
Sixteen students of the University or corrected-to-normal vtsion.
of Letden served as paid subjects.
All had normal
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Materrals The same stimuli grating, consistmg of superimposed on the the contrast between Procedure The procedure
were used as m experiment 1 The only difference was that a a matrix of 9 x 32 points (0.42 by 1.56 degree m visual angle) was target word. The effect of this grating was a strong reduction of the target letters and the background
was identical
to the one used m experiment
1.
Results
The raw data were treated m the same way as m experiment 1, with the only difference that Instead of a 1000 msec cntenon, a 1500 msec cut-off criterion was used (the same criterion as used m the picture-nammg tasks of La Hei1 (1988a)). The 1500 msec criterion, the 3-SD criterion and the trials m which the voice key failed to trigger or tnggered to early accounted for 0.2%, 1.5% and 2.8% of the data, respectively. Table 3 shows the mean RTs and percentages of errors in the SIX distractor condittons An overall analysis of vanance was conducted over the mean RTs with distractor condtttons as withm-subjects factor. This factor reached significance (F(5,75) = 3 2; p < 0 05). In a subsequent Duncan post-hoc test only the differences between the CONTR condition and the five other distractor conditions reached significance at the 0.05 level A separate analysis of vanance over the data of the distractor conditions REL/RS, UNR/RS, REL/NRS and UNR/NRS, with response set memberslnp and semantic relation as withm-subjects factors showed no stgmficant effects (all ps > 0.25). Finally, the effect of target degradation on the overall mean response latency was evaluated m an analysis of variance on the combined data of expenments 1 and 2, with the absence or presence of a supenmposed grating as a between-sublects factor. This factor reached sigmficance (F(1,30) = 23.6; p -C 0 001) The mean response latenctes m experiment 1 and 2 were 574 msec and 646 msec, respectively
The superimposed grating was successful m reducing the legibthty of the target words as indicated by the fact that the overall mean reading latency was stgmficantly larger than m experiment 1 Moreover, the degradatton resulted m a mean response latency (646 msec) simrlar to the one observed m the correspondmg picture nammg task (634 msec). Despite this increase m word-reading times, however, the results of the present expenment clearly differ from those obtained with picture nammg Whereas m the picture nammg task all distractor charactenstics (semantic stmtlanty, response set membership, semantic relevance and wordness) significantly affected the naming latencies, only the factor wordness reached sigmficance in the present word-reading task The conclusion has to be that even when word reading takes as much time as picture nammg and, consequently, an equal amount of time is available for the semantic
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processing of the distractor word, the differences between the context effects in reading and nammg tasks are not elimmated.
Experiment 3 A second posstble mampulation to ensure that there is enough time available for the processing of the distractor word, is to present the distractor word m advance of the target. In the present experiment an SOA of 250 msec is used, an SOA that is small enough to affect the naming of targets m the picture-word interference task (W.R. Glaser and Diingelhoff 1984). It should be noted that the mtroduction of an SOA renders the task similar to a classical pruning task as used by, for example, Lupker (1984). In his experiment 3, m winch also an SOA of 250 msec was used, a semantic pnmmg effect of 6 msec was obtained that reached sigmftcance m the standard analysis but failed to reach sigmficance in the F’ analysis. For that reason we may expect a small amount of semantic facdltatron m the present expenment. A possibly important difference, however, between Lupker’s (1984) study and the present experiment is m the size of the target set. Lupker used 72 different target words, selected from SIX semantic domains, whereas m the present experiment only six target words are selected from only two semantic domains. The results of the experiments reported by La HeiJ et al. (1985) suggest that pnmmg effects diminish with a decrease m the number of targets and the number of semantic domams from which they are selected. As a consequence, the small semantic pnmmg effect observed by Lupker m&t fail to show up m the present experiment, or might even reverse into a semantic interference effect. Method Subjects Sixteen students of the University of Leaden served as paid subJects. All had normal or corrected-to-normal vision. Materrals The same stimuli were used as m experiment 1 Procedure The distractor word was presented 250 msec m advance of the target. Since prime and target duration were kept at 150 msec, the inter-stimulus interval (ISI) was 100 msec. The subjects were asked to read as fast as possible the word which appeared second and which was localized either above or below the central fixation point. In all further respects, the procedure was identical to the one m experiment 1.
The data were treated m the same way as m experiment 1. The 1000 msec cntenon, the 3-SD cntenon and the tnals m which the voice key failed to tngger or triggered too
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early accounted for 1.48, 0.9% and 1 2% of the data, respecttvely. The mean RTs and percentages of errors m the SIX dtstractor condrttons are shown m table 3 An overall analysis of vanance was conducted on the mean RTs wtth drstractor condrttons as wrthin-subjects factor. The mam effect of this factor was far from stgmftcant (p > 0.70). Also m the separate analysrs of variance on the data of the dtstractor condtttons REL/RS, UNR/RS, REL/NRS and UNR/NRS, with response set membershrp and semanttc relation as wtthm-sublects factors no srgmfrcant effects were found. DLSCUSSIO~
The mtroductton of a time delay between the presentation of the dtstractor and the target clearly did not result m a pattern of results stmrlar to the one obtained m the ptcture-narnmg task of La Hen (1988a). The analyses of variance show that this mampulatton even results m a complete elimmatton of all context effects that could be observed m the naming task. The effect of a semantic relation between dtstractor and target was virtually zero. That is, neither a semantic Interference effect, nor a semantic facthtatton effect was obtained. As m expenments 1 and 2 also the dtstractor charactensttcs semantic relevance and response set membershrp dtd not affect performance. A new fmdmg m the present experiment 1s the lack of a difference between the IRR and CONTR condrttons Since dtstractor words that are presented 250 msec m advance of the target do affect ptcture-nammg latenctes as compared to a nonword control, this fmdmg again shows the relattve mvulnerabthty of the word-reading response.
General discussion In this study we evaluated a prediction that can be derived from a name-retrieval account of semantic interference effects in color- and picture-naming tasks. This prediction is that interference due to the two semantic characteristics of the distractor word (semantic relatedness and semantic relevance) will diminish or even disappear when instead of a picture-naming task a word-reading task is used. Recent results reported by W.R. Glaser and Glaser (1989) confirm the prediction that the effect of semantic relatedness disappears in a word-reading task. The effect of semantic relevance could not be assessed in their study, however. In the present series of word-reading tasks we examined the effects of four distractor characteristics: semantic similarity, semantic relevance, response set membership and wordness. A comparison between the picture-naming task of La HeiJ (1988a) and experiment 1 of the present study reveals that reading and naming
W L.a HerJ et al / Stroop-like interference rn word readrng
127
are indeed differentially affected by the two semantic characteristics of the distractor word. First, whereas a semantic relation between distractor and picture hampers the naming of the picture, this factor fails to reach significance when a target word has to be read. It should be noted that the difference was not large (a highly significant 16 msec interference effect with the pictures versus a nonsignificant 9 msec interference effect with the corresponding words). The lack of a significant effect of semantic relatedness in experiment 1 is, however, in accordance with a similar finding in the studies of W.R. Glaser and Glaser (1989: experiment 6) and Underwood and Briggs (1984). Second, whereas the semantic relevance of the distractor word strongly affected the picture-naming times in the study of La Heij (1988a), such an effect is completely absent in our present word-readmg tasks. A third finding was the lack of an effect of response set membership of the distractor word. This finding may be due to the fact that in the present series of experiments six target words were used: La Heij at al. (1985) have shown that this type of interference disappears somewhere between two and twelve response alternatives. There is no doubt, however, that an effect of response set membership can be observed in word- and letter-reading tasks (see La Heij and Vermeij 1987). The effect of wordness (the difference between the IRR and CONTR conditions) reaches significance both in the naming tasks of La Heij (1988a) and in the present experiments 1 and 2. It should be noted that this finding does not imply that this interference effect has similar causes in reading and naming tasks. One important difference between the two tasks is that when two words are presented the target has to be selected on the basis of its relative display position, whereas in the naming task the difference between the visual characteristics of the two display elements can be used as an additional selection cue. The fact that this interference effect decreased in experiment 2, in which the grating could be used as an additional selection cue and disappeared m experiment 3, in which order of presentation could be used as an additional selection cue, provides some support for this interpretation. In line with the conclusion of W.R. Glaser and Glaser (1989), cited above, the present experiments show that the word-word variant of the Stroop task is not as similar to the original Stroop task as initially thought. Most importantly, whereas picture- and color-naming times are strongly affected by the semantic properties of the distractor word,
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word-reading seems to be rather immune to this factor. Since important difference between word-reading and picture-naming is the ease with which verbal responses are accessed, this finding is accordance with a name-retrieval account of semantic interference picture and color naming.
an m in in
References Dalrymple-Alford, E C. and J Azkoul, 1972. The locus of Interference m the Stroop and related tasks. PerceptIon & Psychophyslcs 11, 385-388 Egeth, H E , D L Blecker and A S Kamlet, 1969 Verbal Interference m a perceptual comparison task PerceptIon & PsychophysIcs 6, 355-356 Flowers, J H and S Dutch, 1976 The use of visual and name codes m scannmg and classlfymg colors Memory & Cogmtlon 4, 384-390 Fox, LA, R E. Shor and R J Stemman, 1971 Semantic gradients and Interference m nammg color, spatial dIrectIon, and numerosrty Journal of Expenmental Psychology 91, 59-65 Glaser, M 0. and W R Glaser, 1982 Time course analysis of the Stroop phenomenon Journal of Expenmental Psychology Human PerceptIon and Performance 8, 875-894 Glaser, W R and F -J Dungelhoff, 1984 The time course of picture-word Interference Journal of Expenmental Psychology Human PerceptIon and Performance 10, 640-654 Glaser, W R and M 0. Glaser, 1989 Context effects m Stroop-hke word and picture processmg Journal of Expenmental Psychology. General 118, 13-42. Hock, H S and H.E Egeth, 1970. Verbal Interference with encodmg m a perceptual classlflcatlon task Journal of Expenmental Psychology 83, 299-303 Humphreys, G.W , M.J hddoch and PT. Qumlan, 1988 Cascade processes m picture Identlhcatlon Cogmtlve Neuropsychology 5, 67-103. Huttenlocher, J and L F Kublcek, 1983 The source of smulanty effects on nammg latency Journal of Expenmental Psychology Learmng, Memory, and Cogmtlon 9, 486-496 Keele, SW., 1972. Attention demands of memory retneval Journal of Expenmental Psychology 93, 245-248. Klein, G S., 1964 Semantic power measured through the interference of words with color-nammg. Amencan Journal of Psychology 77, 576-588 La HeIJ, W , 1988a. Components of Stroop-hke Interference m picture nammg. Memory & Cogmtlon 16, m-410. La H~IJ, W., 1988b Lexlcal context effects m readmg and nammg Unpubhshed doctoral dlssertatlon Umverslty of Leaden, Leaden, The Netherlands. La He& W and M VermelJ, 1987 Reading versus naming The effect of target set size on contextual Interference and faclhtatlon PerceptIon & Psychophysics 41, 355-366 La Helj, W., A H C van der HelJden and R Schreuder, 1985 Semantic pnmmg and Stroop-like interference m word-nammg tasks Journal of Expenmental Psychology Human PerceptIon and Performance 11, 62-80 Lupker, S J., 1982. The role of phonetic and orthographic smulanty m picture-word interference Canadian Journal of Psychology 36, 349-367 Lupker, S.J, 1984 Semantic pnmmg wlthout assoclatlon A second look Journal of Verbal Learning and Verbal Behavior 23, 709-733 Lupker, S.J and A.N. Katz, 1981. Input, declslon, and response factors m picture-word mterference Journal of Expenmental Psychology Human Leammg and Memory 7, 269-282
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McCauley, C , C M Parmelee, R D Sperber and T H Cam, 1980 Early extractton of meanmg from ptctures and tts relatton to consctous tdenttftcation Journal of Expenmental Psychology Human Perceptton and Performance 6, 265 -276 Meyer, D E, R W. Schvaneveldt and M G Ruddy, 1975 ‘LOCI of contextual effects on vtsual word recogmtton In P M.A Rabbttt and S Domtc (eds ), Attentton and performance V New York: Academtc Press Neumann, 0, 1980 lnformattonsselectton und Handlungssteuerung [Selectton of mformatton and control of actton]. Unpublished doctoral dtssertatton Umversrty of Bochum, FRG Neumann, 0, 1986 Facthtattve and mhtbttory effects of ‘semantic relatedness’ Report No 111/1986, Research group on ‘Perceptton and Actton’, Umverstty of Btelefeld, FRG Prttchatt, D , 1968 An mvesttgatton mto some of the underlymg assoctattve verbal processes of the Stroop colour effect. Quarterly Journal of Expenmental Psychology 20, 351-359 Rayner, K and C J Spnnger, 1986 Graphemtc and semanttc stmtlanty effects m the picture-word Interference task Bntrsh Journal of Psychology 77, 207-222 Seymour, P H.K, 1973 A model for readmg, nammg and compartson Brmsh Journal of Psychology 64, 35-49 Seymour, P H K , 1977 Conceptual encodmg and locus of the Stroop effect Quarterly Journal of Expenmental Psychology 29, 245-265 Sttrlmg, N , 1979 Stroop interference. An Input and an output phenomenon. Quarterly Journal of Expenmental Psychology 31, 121-132 Stroop, JR, 1935. Studtes of Interference m senal verbal reactions Journal of Expertmental Psychology 18, 643-661 Underwood, G and P Bnggs, 1984 The development of word recogmtton processes Brtttsh Journal of Psychology 75, 243-255 Van der Hegden, A H C , 1981. Short-term vtsual mformatton forgettmg. London: Routledge and Kegan Paul Vnzt, R A and H E Egeth, 1985 Toward a translattonal model of Stroop interference Memory & Cogmtton 13, 3044319 Warren, C and J. Morton, 1982 The effects of pnmmg on picture recogmtton Bnttsh Journal of Psychology 73, 117-129. West, R F and K E Stanovtch, 1982 Source of mhtbttton m expenments on the effect of sentence context on word recogmtton. Journal of Expenmental Psychology Learmng, Memory, and Cogmtton 5, 385-399
Acta Psychologica 73 (1990) 115-129 North-Holland
COMPONENTS OF STROOP-LIKE IN WORD READING * Wido LA HEIJ,
Bart HAPPEL
INTERFERENCE
and Marcel MULDER
Unruersrty of L.erden, The Netherlan& Accepted June 1989
Previous research has shown that the naming of the picture of, for example, a guitar is substantially delayed when tt is accompamed by the name of an obJect from the same semantic category (e g , PIANO) as compared to a nonword control (e.g , xxxxx) La HeiJ (1988a) has shown that a large part of this Stroop-hke mterference effect can be attnbuted to two semantic characteristics of the distractor word: tts semantic stmilarity to the target picture and tts semantic relevance m the task at hand. Furthermore, tt was argued that the locus of these two interference effects is the process of target-name retneval. If this ts true, semanttc interference effects should dimuush or disappear when, Instead of a ptcture-naming task, a word-reading task is used In the present study thts predictton ts tested The effects of four distractor charactensttcs are exammed semantic relatedness, semanttc relevance, response set membershtp and wordness In contrast to the ongmal picture-nammg task only the effect of wordness reached sigmftcance. The results of experiments 2 and 3 show that the absence of sigmftcant semantic context effects m experiment 1 1s not simply due to the fact that a distractor word has less time to affect a word-reading response. The results are taken to support a name-retneval account of semanttc interference m color and picture nammg
Introduction In the original Stroop task, subjects are required to name the color of color patches and of incongruently colored color words (e.g., the word RED printed in green ink). Compared to the naming of color patches, the latter situation results in a remarkable increase in naming latency. Ever since the introduction of this task in psychology (Stroop 19354 attempts have been made to determine the locus or loci of this interference effect. Recently, Stroop interference has mainly been attributed to a rather peripheral process of response competition and/or * Requests for reprints should be sent to W. La HetJ. Faculty of Social Sciences, Umt of Expenmental and Theoretical Psychology, University of Letden, P 0 Box 9555, 2300 RB Leaden, The Netherlands OOOl-6918/90/$3.50 0 1990, Elsevier Sctence Publishers B.V (North-Holland)
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to interference m a semantic decision stage (see, e.g., W.R. Glaser and Diingelhoff 1984; Lupker and Katz 1981; Rayner and Springer 1986; Seymour 1977). Information concerning the locus or loci of Stroop interference can be derived from studies in which attempts were made to determine which dtstractor characteristics affect the amount of interference. Klein (1964; see also Fox et al. 1971) showed that, as compared to nonsense syllables, the following sets of distractor words induced an increasing amount of interference on color nammg: (a) rare English words (e.g., SOL), (b) common English words (e.g., PUT), (c) incongruent color-related words (e.g., LEMON in red ink), (d) color words that did not name one of the target colors in the experiment (e.g., TAN in red ink), and (e) incongruent color words that did name one of the target colors m the experiment (e.g., GREEN in red ink). The increase in interference from condition (a) to (e) is referred to as the ‘semantic gradient’. Klein’s results have often been interpreted to indicate that the amount of interference increases with the strength of the semantic relation between the word and the accompanying color. Neumann (1980), however, pointed out that the effect of a semantic relation between distractor and target cannot be determined in the original Stroop task, due to its confounding with other distractor characteristics. For example, in Klein’s (1964) experiment the distractor word GREEN not only differs from the distractor word PUT in the fact that the word GREEN is semantically related to the accompanymg color (e.g., red), but also in two other respects. First, the word GREEN is a member of the small set of response alternatives in the experiment (a characteristic that will be referred to as response set membershzp). Second, the word GREEN is highly relevant in a task m which colors have to be named (a characteristic that will be referred to as semantic relevance). In a picture-word variant of the Stroop task, using an experimental design developed by Neumann (1980), La HeiJ (1988a) disconfounded the effects of semantic similarity, semantic relevance, response set membership, and ‘wordness’ (the distractor being a word or a series of Xs). The results showed that all of these distractor characteristics attributed significantly to the overall Stroop interference effect. An important finding was that the interference effect due to a semantic relation between distractor and target was very small as compared to the combined effects of semantic relevance, response set membership and wordness. On average, only 13% of the overall interference effect could be attributed to this factor.
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La Heij (1988a) argued that this finding indicates that a large part of the overall Stroop interference effect is not due to a semantic relation between distractor and target, and cannot - for that reason - be attributed to the extra time needed to resolve a ‘semantic ambiguity’, as suggested in the semantic-decision account of Stroop interference. Moreover, it was argued that even the effect of semantic similarity might not be due to interference m a semantic-decision stage. This conclusion was based on two findings in the literature. First, a substantial number of studies have shown that Stroop interference can be eliminated when, instead of verbal naming responses, non-naming responses like button pressing or manual sorting are required. 1 This result suggests that Stroop interference has to do wtth the retrieval and/or production of a verbal naming response. Second, Rayner and Springer (1986) have shown that semantic interference effects in a picture-word interference task disappear when the drstractor word 1s graphemically similar to the prcture’s name, a characteristic of the distractor that is supposed to facilitate the process of name retrieval (see, e.g., Lupker 1982). As an alternative, it was suggested that the effects of semantic similarity and semantic relevance are localized at the level of targetname retrieval (see also La Heij 1988b; W.R. Glaser and Glaser 1989). Within the framework of recent models of picture processing (e.g. W.R. Glaser and Glaser 1989; Warren and Morton 1982; Humphreys et al. 1988) interference in name-retrieval may be thought of as the result of inhibitory interactions within the lexicon: the activation of the phonological representation of the context word inhibits or temporarily ‘blocks’ the activation of the phonological representation of the picture’s name. The fact that a word that is categorically related to the target picture induces more interference than an unrelated word could then be attributed to ‘reverse priming’ (Neumann 1986): the semantic representation of the picture mcreases the activation level of the phonological representation of the context word, either due to a spread ’ Stroop Interference was ehmmated by usmg non-verbal or non-nammg responses m the studies of, for example, Egeth et al. (1969), Flowers and Dutch (1976), and VNZJ and Egeth (1985) In a number of other studies, however, this marupulatlon reduced but not completely ehmmated Stroop mterference (e g., Hock and Egeth 1970, Keele 1972, Prltchatt 1968, see also Stwhng 1979). A plausible explanation for most of these residual Stroop Interference effects IS that subjects used covert nammg responses The reader IS referred to Dalrymple-Alford and Azkoul (1972) and La HeI] (19881, 141-152) for a dIscussIon of this Issue
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of activation within a semantic system (as assumed in the model of W.R. Glaser and Glaser (1989)) or due to the fact that m the process of picture-name retrieval a number of categorically related words get activated, including the one that is already activated by the context word. In the present study we will examine a prediction that can be derived from this name-retrieval account. In most models of picture and word processing (e.g., W.R. Glaser and Glaser 1989; Seymour 1973; Van der Heijden 1981; Warren and Morton 1982), it is assumed that an important difference between the reading of words and the naming of pictures is the ease with which phonological representations are activated. In discussing the two general processing stages that are involved in picture naming - picture identification and name retrieval - McCauley et al. (1980) for instance, noted: ‘the first stage, in which contact is made with semantic memory, seems to be automatic, but the second stage appears to require an investment of attention to consult the internal lexicon for a name. This stands m marked contrast to evidence that when stimuli are words, their stored phonetic codes.. . as well as their stored semantic codes _. . can be activated automatically’ (1980: 274). Hence, if the distractor characteristics semantic relatedness and semantic relevance interfere in the process of picture-name retrieval, the prediction can be derived that these effects will diminish or even disappear when instead of a picture-naming task, a word-reading task is used. A task that is relevant for evaluating this prediction is the word-word variant of the Stroop task; a task in which two color words are presented, one of which has to be read aloud (M.O. Glaser and Glaser 1982; Van der Heijden 1981). At first sight the results of these studies do not seem in accordance with the above prediction: despite the fact that subjects were asked to read a color word instead of naming a color, incongruent distractor words induced a full-blown Stroop interference effect. The similarity between the color-word and word-word variant of the Stroop task made M.O. Glaser and Glaser hypothesize that ‘the same cognitive process underlies word-word.. . and wordcolor conflicts (color component relevant)’ (1982: 888). It should be noted, however, that Van der Heijden (1981) and M.O. Glaser and Glaser (1982) used only three distractor conditions: incongruent (e.g., RED-GREEN), control (e.g., XXX-GREEN), and congruent (e.g., GREEN-GREEN). The finding that the word RED hampers the reading of the target word GREEN as compared to a string of Xs does
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not imply that the interference is semantically based. This issue was recently examined by W.R. Glaser and Glaser (1989). These authors investigated whether an important characteristic of Stroop interference _ Klein’s (1964) semantic gradient - also shows up in a word-word variant of the Stroop task. Their main finding was summarized as follows: ‘the surprising result was that the semantic gradient showed up with only residual values of less then 10 ms. That means that the pairing conditions of distractor and target that provide gradually different inhibitions in the naming task were essentially ineffective in the reading task with word distracters’ (1989: 40). Of most interest is their finding that in a word-reading task the presence of a semantic relation between a distractor word and a target word does not affect response latencies. As argued above, this result is in accordance with a name-retrieval account of semantic interference in picture and color naming. Unfortunately, m the experiments reported by W.R. Glaser and Glaser (1989) a number of distractor characteristics remain confounded. Most importantly, in none of their experiments the effect of the semantic relevance of a distractor word can be assessed. Therefore, in experiment 1, we examine the effects of the distractor characteristics semantic relatedness, semantic relevance, response set membership, and wordness in a word-reading task. In experiments 2 and 3 a possible explanation for the lack of significant semantic interference effects in experiment 1 is evaluated.
Experiment 1 Thts expenment 1s very sumlar to one of the picture-word interference expenments reported by La Hen (1988a) The only important difference is that the target ptctures were replaced by the correspondmg words. SIX target words were selected from two semantic categories: frutts and parts of the body. The followmg dtstractor condtttons were used (see also table 1) (1) related/response set (REL/RS) the dtstractor word 1s related to the target word and 1s part of the response set (e.g., CHERRY (dlStGiCtOr)-PEAR (target)); (2) related/not m response set (REL/NRS): the dtstractor word IS related to the target word but 1s not part of the response set (e.g , GRAPE-PEAR); (3) unrelated/ response set (UNR/RS) the dtstractor word IS unrelated to the target word and IS part of the response set (e.g., NOSE-PEAR), (4) unrelated/not m response set (UNR/NRS). the dtstractor word IS unrelated to the target word and not part of the response set (e.g., HAND-PEAR); (5) irrelevant (IRR): the dtstractor word 1s not a member of the two
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Table 1 Examples of the SIX target-dlstractor combmatlons used m expenment 1 and then charactenstlcs The presence (+) or absence (- ) of the correspondmg charactenstlc IS mdlcated Target
PEAR
DIstractor
BANANA
MOUTH
LEMON
HAND
DOOR
+
_
+
-
_
SemantIcally related to the target word Part of the response set Member of a relevant semantic category a
+
+
-
-
_
+
+
+
+
_
Condltlon
REL/RS
UNR/RS
REL/NRS
UNR/NRS
IRR
label
a The relevant
relevant
semantic
semantic
categones
categones
XXXXX
CONTR
were frmts and parts of the body
frutts
and
body
parts
but
IS a
member
of
a
thtrd,
(6) control (CONTR). the distractor is a senes of five Xs. These SIX distractor conditions allow the exammatton of four kmds of context effects. semantic relatedness (the difference between the REL and UNR conditions), semantic relevance (the difference between the UNR/NRS and IRR conditions), response set membership (the difference between the RS and NRS conditions), and wordness (the difference between the IRR and CONTR conditions) Except for the use of target words instead of target pictures, the stimulus material 1s identical to part of the stimulus matenal used by La Hei1 (1988a: experiment 2, set 2). The data obtained with the correspondmg pictures and distractor words m that study were clear. separate analyses of variance and a Newman-Keuls test showed that all four context effects reached significance. For ease of companson, the results of this picture nammg task are shown m the top row of table 3. Irrelevant,
category
(e.g.,
DOOR-PEAR);
Method
subjects Sixteen students of the University of Leaden served as paid subjects. All had normal or corrected-to-normal vision.
Matertals The Enghsh translattons of the dtstractor-target pairs are shown m table 2. The dtstractor word was always presented at the point of fixation. The target word could appear either above or below the distractor. Distance between the nearest contours of the words was 0.26 degree of visual angle The length of the words ranged from 0.80 degree of visual angle (three-letter word) to 1 86 degree of visual angle (seven-letter word). Viewing distance was 60 cm.
W L.u Her/ et al / Stroop-lake rnterference MIword readrng Table 2 The target-dlstractor and 3 Target
PEAR
CHERRY
BANANA
FINGER
NOSE
MOUTH
DIstractor
combmatlons
used m the vartous
dlstractor
condltlons
121
of experiments
1, 2,
condltlon
REL/RS
UNR/RS
REL/NRS
UNR/NRS
IRR
CONTR
CHERRY
NOSE
GRAPE
EAR
DOOR
XxXxX
BANANA
MOUTH
LEMON
HAND
LOFT
xXxXx
PEAR
FINGER
APPLE
FOOT
WINDOW
xXxXx
BANANA
MOUTH
LEMON
HAND
LOFT
XxXxX
PEAR
FINGER
APPLE
FOOT
WINDOW
xXxXx
CHERRY
NOSE
GRAPE
EAR
DOOR
xXxXx
NOSE
CHERRY
EAR
GRAPE
DOOR
xxxxx
MOUTH
BANANA
HAND
LEMON
LOFT
XXXXX
FINGER
PEAR
FOOT
APPLE
WINDOW
XXXXX
MOUTH
BANANA
HAND
LEMON
LOFT
XxXxX
FINGER
PEAR
FOOT
APPLE
WlNDOW
xxxxx
NOSE
CHERRY
EAR
GRAPE
DOOR
XXXXX
Apparatus
The stimuli were presented on a fast display screen (GT40). Verbal reading latencies were measured by means of a voice key with an accuracy of 1 msec. Presentation and regrstratton of reaction times and errors was controlled by a PDP 11/40 computer
Procedure
Subjects were run mdtvtdually m a dimly lllummated room. At the start of the session they were informed about the SIX words that would serve as targets m the experiment. They were acquainted with the task m a senes of 25 practice trials. Each trial mvolved the following sequence. a dtm flxatton point (asterisk) appeared between two bars m the center of the screen. After pressing a button and an interval of 500 msec, the dtstractor appeared at the pomt of ftxatron and the target word appeared either above or below the distractor. Dtstractor and target remained on the screen for 150 msec. The subJects were told to ignore the dtstractor and to name the word that appeared above or below the dtstractor as fast as posstble whtle retaining accuracy. After each tnal the experimenter entered a code mto the computer to indicate whether the response was correct or false. A distinction was made between incorrect responses (wrong name, the mltratton of a wrong name, or a hesttatron sound like ‘eh’) and cases m whtch the voice key dtd not tngger or triggered too early. A session Involved two blocks of 144 trials (6 target words x 6 dtstractor condtttons x 2 drstractor words per condttron X 2 postttons X 2 rephcatlons). The sttmuh were presented m random order with the restrtctton that a target word was never presented twice m succession. In order to reduce the vanance m the data each block was preceded by four warming-up tnals and each incorrect response was followed by a filler trial. The results of the warming-up and filler tnals were not included m the analyses.
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Table 3 Mean RTs (msec) and error percentages (m parentheses) m the various picture-nammg task reported m La HelJ (1988a) and of the three reported m the present study
dlstractor condltlons of the word readmg expenments
REL/RS
UNR/RS
REL/NRS
UNR/NRS
IRR
CONTR
La HeiJ (1988a) picture
nammg
660 (3 6)
646 (2 5)
649 (1 4)
631 (2 0)
618 (1 0)
600 (1 8)
Expenment Expenment Expenment
1 2 3
584 (0 1) 652 (5 6) 544 (2 3)
576 (0 0) 644 (4 8) 546 (1 4)
584 (0.2) 648 (4.8) 542 (0 6)
574 (0 1) 647 (4 4) 540 (0 3)
583 (0 2) 650 (4 8) 542 (0.4)
541 (0 0) 635 (5 2) 542 (0 0)
Results The raw data were treated as follows: first, RTs of Incorrect reactions and RTs longer than 1000 msec were excluded Next, for each subject, means and standard deviations were calculated for each of the SIX distractor conditions. RTs that deviated more than three standard deviations from their cell mean were excluded. The remaining RTs were used m the calculation of the means. The 1000 msec criterion, the 3-SD criterion, and the trials in which the voice key failed to trigger or triggered too early accounted for 0.8%, 1 l%, and 0.7% of the data, respectively. Table 3 shows the mean RTs and percentages of errors m the six distractor conditions An overall analysis of vanance was conducted on the mean RTs with distractor conditions as within-subjects factor. This factor reached sigmficance (F(5,75) = 19.9; p < 0.001). In a subsequent Duncan post-hoc test, only the differences between the CONTR condition and the five other distractor conditions reached significance at the 0.05 level A separate analysis of vanance over the data of the distractor condrtions REL/RS, UNR/RS, REL/NRS and UNR/NRS, with response set membership and semantic relation as within-subjects factors showed no significant effects. The factor semantic sm-ulanty only approached sigmficance (F(1,15) = 4.5; p < 0 06) (mean RTs were 584 msec and 575 msec m the REL and UNR conditions, respectively). As can be seen m table 3, very few errors were made. Dmx.wton
The SIX distractor conditions used m this sxpenment allow the exammation of the effects of four distractor charactenstics. semantic relatedness (REL-UNR), semantic relevance (UNR/NRS-IRR), response set membership (RS-NRS), and wordness (IRR-CONTR). Of these effects, only the last one reached sigmficance. This fmdmg stands m marked contrast to the results obtained m the correspondmg picture-nammg task of La Heij (1988a), in which all four distractor characteristics induced significant interference effects. So, by changmg the task from picture nammg to word reading, (a)
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the effect of semantic similarity decreased and failed to reach sigmftcance m the analysis of vanance, a fmdmg that 1s m accordance wtth the result of W.R. Glaser and Glaser (1989: experiment 6), (b) the effect of semantic relevance reversed m dtrection, but also faded to reach stgmftcance, and (c) the effect of response set membership disappeared. Underwood and Bnggs (1984. experiment 2) also presented a target word and a dtstractor word stmultaneously, one at the left and one at the right of a central ftxation point. The sublects were mstructed to read the word that appeared m a rectangular box The distractor word was (a) semantically associated to the target (e g., LOAFBREAD), (b) graphemically similar to the target (e.g, BEAD-BREAD), (c) phonemically stmtlar to the target (e.g., FLED-BREAD), (d) unrelated to the target (e g., RISK-BREAD), or (e) a nonword (e.g., HBTM-BREAD) Adult readers showed no stgmftcant differences between these five distractor condtttons. A group of sublects referred to as ‘young poor readers’ (aged between 9 and 12 years old), however, showed a substantial semantic interference effect. That ts, dtstractor words that were semantically associated to the target induced interference as compared to unrelated dtstractor words. In discussmg this fmdmg, Underwood and Bnggs (1984) noted: ‘the poor readers show semantic interference m the word-nammg task, it 1s suggested, because their slow articulatory planning allows ttme for the identiftcation of the meaning of the distractor Readers of greater skill are not vulnerable to interference because they can identify and name the target word either before the semantic processmg of the dtstractor 1s complete, or by bypassing the lextcal route altogether’ (1984: 252) (see also Huttenlocher and Kubicek 1983; West and Stanovich 1982). The difference between the context effects observed m the picture-nammg task of La Heil (1988a) and the present word-reading task may be explained m a stmtlar way. That ts, the absence of sigmftcant semantic context effects m the present experiment may be due to the fact that m a word-reading task less ttme 1s available for the semantic processmg of the dtstractor word (the overall mean word-reading latency m the present expenment was 60 msec smaller than the correspondmg mean picture-nammg latency; see table 3). Thts hypothesis will be exarmned in the next two expenments.
Experiment 2 Two mampulattons can be thought of to ensure that the semantic processmg of the distractor word is completed before a response is nnttated m our present word-reading task. First, the legibthty of the target word can be reduced, resultmg m longer reading latenctes. Second, the distractor word can be presented m advance of the target. In the present expenment we will examme the effect of the first mampulation. Target degradation was achieved by supertmposmg a gratmg of whtte dots on the target (see Meyer et al. (1975) for a sumlar procedure). Method SubJects
Sixteen students of the University or corrected-to-normal vtsion.
of Letden served as paid subjects.
All had normal
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Materrals The same stimuli grating, consistmg of superimposed on the the contrast between Procedure The procedure
were used as m experiment 1 The only difference was that a a matrix of 9 x 32 points (0.42 by 1.56 degree m visual angle) was target word. The effect of this grating was a strong reduction of the target letters and the background
was identical
to the one used m experiment
1.
Results
The raw data were treated m the same way as m experiment 1, with the only difference that Instead of a 1000 msec cntenon, a 1500 msec cut-off criterion was used (the same criterion as used m the picture-nammg tasks of La Hei1 (1988a)). The 1500 msec criterion, the 3-SD criterion and the trials m which the voice key failed to trigger or tnggered to early accounted for 0.2%, 1.5% and 2.8% of the data, respectively. Table 3 shows the mean RTs and percentages of errors in the SIX distractor condittons An overall analysis of vanance was conducted over the mean RTs with distractor condtttons as withm-subjects factor. This factor reached significance (F(5,75) = 3 2; p < 0 05). In a subsequent Duncan post-hoc test only the differences between the CONTR condition and the five other distractor conditions reached significance at the 0.05 level A separate analysis of vanance over the data of the distractor conditions REL/RS, UNR/RS, REL/NRS and UNR/NRS, with response set memberslnp and semantic relation as withm-subjects factors showed no stgmficant effects (all ps > 0.25). Finally, the effect of target degradation on the overall mean response latency was evaluated m an analysis of variance on the combined data of expenments 1 and 2, with the absence or presence of a supenmposed grating as a between-sublects factor. This factor reached sigmficance (F(1,30) = 23.6; p -C 0 001) The mean response latenctes m experiment 1 and 2 were 574 msec and 646 msec, respectively
The superimposed grating was successful m reducing the legibthty of the target words as indicated by the fact that the overall mean reading latency was stgmficantly larger than m experiment 1 Moreover, the degradatton resulted m a mean response latency (646 msec) simrlar to the one observed m the correspondmg picture nammg task (634 msec). Despite this increase m word-reading times, however, the results of the present expenment clearly differ from those obtained with picture nammg Whereas m the picture nammg task all distractor charactenstics (semantic stmtlanty, response set membership, semantic relevance and wordness) significantly affected the naming latencies, only the factor wordness reached sigmficance in the present word-reading task The conclusion has to be that even when word reading takes as much time as picture nammg and, consequently, an equal amount of time is available for the semantic
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processing of the distractor word, the differences between the context effects in reading and nammg tasks are not elimmated.
Experiment 3 A second posstble mampulation to ensure that there is enough time available for the processing of the distractor word, is to present the distractor word m advance of the target. In the present experiment an SOA of 250 msec is used, an SOA that is small enough to affect the naming of targets m the picture-word interference task (W.R. Glaser and Diingelhoff 1984). It should be noted that the mtroduction of an SOA renders the task similar to a classical pruning task as used by, for example, Lupker (1984). In his experiment 3, m winch also an SOA of 250 msec was used, a semantic pnmmg effect of 6 msec was obtained that reached sigmftcance m the standard analysis but failed to reach sigmficance in the F’ analysis. For that reason we may expect a small amount of semantic facdltatron m the present expenment. A possibly important difference, however, between Lupker’s (1984) study and the present experiment is m the size of the target set. Lupker used 72 different target words, selected from SIX semantic domains, whereas m the present experiment only six target words are selected from only two semantic domains. The results of the experiments reported by La HeiJ et al. (1985) suggest that pnmmg effects diminish with a decrease m the number of targets and the number of semantic domams from which they are selected. As a consequence, the small semantic pnmmg effect observed by Lupker m&t fail to show up m the present experiment, or might even reverse into a semantic interference effect. Method Subjects Sixteen students of the University of Leaden served as paid subJects. All had normal or corrected-to-normal vision. Materrals The same stimuli were used as m experiment 1 Procedure The distractor word was presented 250 msec m advance of the target. Since prime and target duration were kept at 150 msec, the inter-stimulus interval (ISI) was 100 msec. The subjects were asked to read as fast as possible the word which appeared second and which was localized either above or below the central fixation point. In all further respects, the procedure was identical to the one m experiment 1.
The data were treated m the same way as m experiment 1. The 1000 msec cntenon, the 3-SD cntenon and the tnals m which the voice key failed to tngger or triggered too
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early accounted for 1.48, 0.9% and 1 2% of the data, respecttvely. The mean RTs and percentages of errors m the SIX dtstractor condrttons are shown m table 3 An overall analysis of vanance was conducted on the mean RTs wtth drstractor condrttons as wrthin-subjects factor. The mam effect of this factor was far from stgmftcant (p > 0.70). Also m the separate analysrs of variance on the data of the dtstractor condtttons REL/RS, UNR/RS, REL/NRS and UNR/NRS, with response set membershrp and semanttc relation as wtthm-sublects factors no srgmfrcant effects were found. DLSCUSSIO~
The mtroductton of a time delay between the presentation of the dtstractor and the target clearly did not result m a pattern of results stmrlar to the one obtained m the ptcture-narnmg task of La Hen (1988a). The analyses of variance show that this mampulatton even results m a complete elimmatton of all context effects that could be observed m the naming task. The effect of a semantic relation between dtstractor and target was virtually zero. That is, neither a semantic Interference effect, nor a semantic facthtatton effect was obtained. As m expenments 1 and 2 also the dtstractor charactensttcs semantic relevance and response set membershrp dtd not affect performance. A new fmdmg m the present experiment 1s the lack of a difference between the IRR and CONTR condrttons Since dtstractor words that are presented 250 msec m advance of the target do affect ptcture-nammg latenctes as compared to a nonword control, this fmdmg again shows the relattve mvulnerabthty of the word-reading response.
General discussion In this study we evaluated a prediction that can be derived from a name-retrieval account of semantic interference effects in color- and picture-naming tasks. This prediction is that interference due to the two semantic characteristics of the distractor word (semantic relatedness and semantic relevance) will diminish or even disappear when instead of a picture-naming task a word-reading task is used. Recent results reported by W.R. Glaser and Glaser (1989) confirm the prediction that the effect of semantic relatedness disappears in a word-reading task. The effect of semantic relevance could not be assessed in their study, however. In the present series of word-reading tasks we examined the effects of four distractor characteristics: semantic similarity, semantic relevance, response set membership and wordness. A comparison between the picture-naming task of La HeiJ (1988a) and experiment 1 of the present study reveals that reading and naming
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are indeed differentially affected by the two semantic characteristics of the distractor word. First, whereas a semantic relation between distractor and picture hampers the naming of the picture, this factor fails to reach significance when a target word has to be read. It should be noted that the difference was not large (a highly significant 16 msec interference effect with the pictures versus a nonsignificant 9 msec interference effect with the corresponding words). The lack of a significant effect of semantic relatedness in experiment 1 is, however, in accordance with a similar finding in the studies of W.R. Glaser and Glaser (1989: experiment 6) and Underwood and Briggs (1984). Second, whereas the semantic relevance of the distractor word strongly affected the picture-naming times in the study of La Heij (1988a), such an effect is completely absent in our present word-readmg tasks. A third finding was the lack of an effect of response set membership of the distractor word. This finding may be due to the fact that in the present series of experiments six target words were used: La Heij at al. (1985) have shown that this type of interference disappears somewhere between two and twelve response alternatives. There is no doubt, however, that an effect of response set membership can be observed in word- and letter-reading tasks (see La Heij and Vermeij 1987). The effect of wordness (the difference between the IRR and CONTR conditions) reaches significance both in the naming tasks of La Heij (1988a) and in the present experiments 1 and 2. It should be noted that this finding does not imply that this interference effect has similar causes in reading and naming tasks. One important difference between the two tasks is that when two words are presented the target has to be selected on the basis of its relative display position, whereas in the naming task the difference between the visual characteristics of the two display elements can be used as an additional selection cue. The fact that this interference effect decreased in experiment 2, in which the grating could be used as an additional selection cue and disappeared m experiment 3, in which order of presentation could be used as an additional selection cue, provides some support for this interpretation. In line with the conclusion of W.R. Glaser and Glaser (1989), cited above, the present experiments show that the word-word variant of the Stroop task is not as similar to the original Stroop task as initially thought. Most importantly, whereas picture- and color-naming times are strongly affected by the semantic properties of the distractor word,
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tn word readtng
word-reading seems to be rather immune to this factor. Since important difference between word-reading and picture-naming is the ease with which verbal responses are accessed, this finding is accordance with a name-retrieval account of semantic interference picture and color naming.
an m in in
References Dalrymple-Alford, E C. and J Azkoul, 1972. The locus of Interference m the Stroop and related tasks. PerceptIon & Psychophyslcs 11, 385-388 Egeth, H E , D L Blecker and A S Kamlet, 1969 Verbal Interference m a perceptual comparison task PerceptIon & PsychophysIcs 6, 355-356 Flowers, J H and S Dutch, 1976 The use of visual and name codes m scannmg and classlfymg colors Memory & Cogmtlon 4, 384-390 Fox, LA, R E. Shor and R J Stemman, 1971 Semantic gradients and Interference m nammg color, spatial dIrectIon, and numerosrty Journal of Expenmental Psychology 91, 59-65 Glaser, M 0. and W R Glaser, 1982 Time course analysis of the Stroop phenomenon Journal of Expenmental Psychology Human PerceptIon and Performance 8, 875-894 Glaser, W R and F -J Dungelhoff, 1984 The time course of picture-word Interference Journal of Expenmental Psychology Human PerceptIon and Performance 10, 640-654 Glaser, W R and M 0. Glaser, 1989 Context effects m Stroop-hke word and picture processmg Journal of Expenmental Psychology. General 118, 13-42. Hock, H S and H.E Egeth, 1970. Verbal Interference with encodmg m a perceptual classlflcatlon task Journal of Expenmental Psychology 83, 299-303 Humphreys, G.W , M.J hddoch and PT. Qumlan, 1988 Cascade processes m picture Identlhcatlon Cogmtlve Neuropsychology 5, 67-103. Huttenlocher, J and L F Kublcek, 1983 The source of smulanty effects on nammg latency Journal of Expenmental Psychology Learmng, Memory, and Cogmtlon 9, 486-496 Keele, SW., 1972. Attention demands of memory retneval Journal of Expenmental Psychology 93, 245-248. Klein, G S., 1964 Semantic power measured through the interference of words with color-nammg. Amencan Journal of Psychology 77, 576-588 La HeIJ, W , 1988a. Components of Stroop-hke Interference m picture nammg. Memory & Cogmtlon 16, m-410. La H~IJ, W., 1988b Lexlcal context effects m readmg and nammg Unpubhshed doctoral dlssertatlon Umverslty of Leaden, Leaden, The Netherlands. La He& W and M VermelJ, 1987 Reading versus naming The effect of target set size on contextual Interference and faclhtatlon PerceptIon & Psychophysics 41, 355-366 La Helj, W., A H C van der HelJden and R Schreuder, 1985 Semantic pnmmg and Stroop-like interference m word-nammg tasks Journal of Expenmental Psychology Human PerceptIon and Performance 11, 62-80 Lupker, S J., 1982. The role of phonetic and orthographic smulanty m picture-word interference Canadian Journal of Psychology 36, 349-367 Lupker, S.J, 1984 Semantic pnmmg wlthout assoclatlon A second look Journal of Verbal Learning and Verbal Behavior 23, 709-733 Lupker, S.J and A.N. Katz, 1981. Input, declslon, and response factors m picture-word mterference Journal of Expenmental Psychology Human Leammg and Memory 7, 269-282
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McCauley, C , C M Parmelee, R D Sperber and T H Cam, 1980 Early extractton of meanmg from ptctures and tts relatton to consctous tdenttftcation Journal of Expenmental Psychology Human Perceptton and Performance 6, 265 -276 Meyer, D E, R W. Schvaneveldt and M G Ruddy, 1975 ‘LOCI of contextual effects on vtsual word recogmtton In P M.A Rabbttt and S Domtc (eds ), Attentton and performance V New York: Academtc Press Neumann, 0, 1980 lnformattonsselectton und Handlungssteuerung [Selectton of mformatton and control of actton]. Unpublished doctoral dtssertatton Umversrty of Bochum, FRG Neumann, 0, 1986 Facthtattve and mhtbttory effects of ‘semantic relatedness’ Report No 111/1986, Research group on ‘Perceptton and Actton’, Umverstty of Btelefeld, FRG Prttchatt, D , 1968 An mvesttgatton mto some of the underlymg assoctattve verbal processes of the Stroop colour effect. Quarterly Journal of Expenmental Psychology 20, 351-359 Rayner, K and C J Spnnger, 1986 Graphemtc and semanttc stmtlanty effects m the picture-word Interference task Bntrsh Journal of Psychology 77, 207-222 Seymour, P H.K, 1973 A model for readmg, nammg and compartson Brmsh Journal of Psychology 64, 35-49 Seymour, P H K , 1977 Conceptual encodmg and locus of the Stroop effect Quarterly Journal of Expenmental Psychology 29, 245-265 Sttrlmg, N , 1979 Stroop interference. An Input and an output phenomenon. Quarterly Journal of Expenmental Psychology 31, 121-132 Stroop, JR, 1935. Studtes of Interference m senal verbal reactions Journal of Expertmental Psychology 18, 643-661 Underwood, G and P Bnggs, 1984 The development of word recogmtton processes Brtttsh Journal of Psychology 75, 243-255 Van der Hegden, A H C , 1981. Short-term vtsual mformatton forgettmg. London: Routledge and Kegan Paul Vnzt, R A and H E Egeth, 1985 Toward a translattonal model of Stroop interference Memory & Cogmtton 13, 3044319 Warren, C and J. Morton, 1982 The effects of pnmmg on picture recogmtton Bnttsh Journal of Psychology 73, 117-129. West, R F and K E Stanovtch, 1982 Source of mhtbttton m expenments on the effect of sentence context on word recogmtton. Journal of Expenmental Psychology Learmng, Memory, and Cogmtton 5, 385-399
