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Disentangling attention from action in the emotional spatial cueing task ab

Manon Mulckhuyse

a

& Geert Crombez

a

Department of Experimental-Clinical and Health Psychology, Ghent University, Ghent, Belgium b

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Experimental Psychology, Helmholtz Institute Utrecht University, Utrecht, The Netherlands Published online: 27 Jan 2014.

To cite this article: Manon Mulckhuyse & Geert Crombez (2014): Disentangling attention from action in the emotional spatial cueing task, Cognition & Emotion, DOI: 10.1080/02699931.2013.878688 To link to this article: http://dx.doi.org/10.1080/02699931.2013.878688

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COGNITION AND EMOTION, 2014 http://dx.doi.org/10.1080/02699931.2013.878688

Disentangling attention from action in the emotional spatial cueing task Manon Mulckhuyse1,2 and Geert Crombez1 1

Department of Experimental-Clinical and Health Psychology, Ghent University, Ghent, Belgium Experimental Psychology, Helmholtz Institute Utrecht University, Utrecht, The Netherlands

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In the emotional spatial cueing task, a peripheral cue—either emotional or non-emotional—is presented before target onset. A stronger cue validity effect with an emotional relative to a nonemotional cue (i.e., more efficient responding to validly cued targets relative to invalidly cued targets) is taken as an indication of emotional modulation of attentional processes. However, results from previous emotional spatial cueing studies are not consistent. Some studies find an effect at the validly cued location (shorter reaction times compared to a non-emotional cue), whereas other studies find an effect at the invalidly cued location (longer reaction times compared to a non-emotional cue). In the current paper, we explore which parameters affect emotional modulation of the cue validity effect in the spatial cueing task. Results from five experiments in healthy volunteers led to the conclusion that a threatening spatial cue did not affect attention processes but rather indicate that motor processes are affected. A possible mechanism might be that a strong aversive cue stimulus decreases reaction times by means of stronger action preparation. Consequently, in case of a spatially congruent response with the peripheral cue, a stronger cue validity effect could be obtained due to stronger response priming. The implications for future research are discussed. Keywords: Emotional attention; Spatial cueing; Response mode; Response priming; Action tendency.

Research has shown that salient visual stimuli, such as sudden onsets, capture attention automatically (Yantis & Jonides, 1984; see for review Theeuwes, 2010). Salient stimuli even capture attention when the stimulus is not contingent on top-down goals (Theeuwes, 1992, 1994, but see Folk, Remington, & Johnston, 1992). Presumably, this mechanism may help us to react adaptively to stimuli in the environment in order to survive. For

example, imagine you are walking in the mountains. In the corner of your eye something grabs your attention. Before you know it, you dive and a rock misses you by an inch. If the falling rock had not captured your attention, you could have been dead. The exogenous spatial cueing paradigm has been designed to measure mechanisms of stimulus (bottom-up)-driven attentional capture (Posner,

Correspondence should be addressed to: Manon Mulckhuyse, Department of Experimental Psychology, Helmholtz Institute Utrecht University, Heidelberglaan 2, 3584 CS Utrecht, The Netherlands. Email: [email protected] This research was funded by a Rubicon grant from NWO (Netherlands Organization for Scientific Research) to M. Mulckhuyse. © 2014 Taylor & Francis

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1980; Posner & Cohen, 1984). In this paradigm, participants fixate a point in the middle of a screen and respond to a target that is presented in one of two placeholders presented at the left and the right of the fixation point. Prior to target presentation, a cue consisting of a sudden onset or the illumination of a placeholder is briefly presented. This cue does not predict the target location and is therefore task irrelevant. Typically, participants respond more efficiently (faster and more accurately) to a target presented at the cued location (validly cued target) than to a target presented at the opposite uncued location (invalidly cued target). This is explained by an automatic shift of attention to the cued location due to the visual salience of the onset cue. Subsequently, visual processing at that location is temporarily facilitated whereas processing at the opposite location is not. Similar to salient visual stimuli, it has been proposed that salient emotional stimuli, such as threatening stimuli, capture attention in a stimulus-driven way (e.g., Öhman, Flykt, & Esteves, 2001; Vuilleumier, 2005). Much research on emotional attention used the dot-probe task to investigate emotional attention processes (Macleod, Mathews, & Tata, 1986). In the dot-probe task two cues are presented (one with an emotional value and the other neutral) after which a probe (target) is presented at one of the locations. Faster responses to targets presented at the emotionally cued location relative to the neutrally cued location indicate an attentional bias towards emotional stimuli (see for review Bar Haim, Lamy, Pergamin, Bakermans-Kranenburg, & van IJzendoorn, 2007). However, it has been suggested that the procedural parameters used in these studies do not allow distinguishing between different components of attention, such as engagement and disengagement (Posner & Petersen, 1990; Yiend, 2010). For example, often a long SOA of 500 ms is used, which allows for multiple shifts of attention. In addition, in most dot-probe studies a baseline measure needed to calculate engagement and disengagement effects is not implemented (Fox, Russo, Bowles, & Dutton, 2001). Other studies have investigated emotional attention with an adaptation of the classic spatial

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cueing paradigm, the so-called emotional spatial cueing paradigm. For example, instead of a salient visual stimulus, a threatening or non-threatening picture or word is presented as a cue stimulus. The idea is that a threatening cue enhances the cueing effect relative to the non-threatening cue. It has been suggested that this is due to stronger engagement of the threatening cue (more efficient processing at the validly cued location) and slower disengagement of the threatening cue (longer dwell time on the threatening cue; Fox et al., 2001). However, results from the emotional spatial cueing studies are less conclusive as to whether threat modulates attention automatically, and as to whether the engagement or the disengagement of attention is affected (Cisler, Bacon, & Williams, 2009; Mogg , Holmes, Garner, & Bradley, 2008; Yiend, 2010). Several emotional spatial cueing studies found a decrease in reaction time to validly cued targets preceded by a threatening cue, indicating faster orienting to a threatening cue relative to a non-threatening cue (Koster, Crombez, Van Damme, Verschuere, & De Houwer, 2004, 2005; Koster, Crombez, Verschuere, Vandamme, & Wiersema, 2006; Koster, Crombez, Verschuere, Vanvolsem, & De Houwer, 2007; Massar, Mol, Kenemans, & Baas, 2011; Van Damme et al., 2004; Van Damme, Crombez, Hermans, Koster, & Eccleston, 2006). Studies by Stormark and Hugdahl (1996; Stormark, Hugdahl, and Posner, 1999) found a decrease in reaction time for responses to invalidly cued targets preceded by a threatening cue, indicating less attentional dwell time on the threatening cue. In contrast, other studies found an increase in reaction time for responses to invalidly cued targets preceded by a threatening cue, indicating a longer attentional dwell time on the threatening cue relative to the non-threatening cue (Koster et al., 2004, 2005; Raes, Koster, Van Damme, Fias, & De Raedt, 2010; Van Damme et al., 2006; Van Damme, Crombez, & Notebaert, 2008). And finally, some studies found this latter effect only in high anxious individuals (Fox et al., 2001; Koster et al., 2006; Massar et al., 2011; Yiend & Mathews, 2001). Of note is that in the above-mentioned studies the original spatial cueing task was modified in

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ATTENTION AND ACTION IN THE EMOTIONAL SPATIAL CUEING TASK

such a way that it may have led to a mixture of both bottom-up (exogenous) and top-down (endogenous) driven attentional processes. First, the task may elicit exogenous attention because of the sudden onset of the cue stimulus, which is known to capture attention due to its visual properties (Yantis & Jonides, 1984) irrespective of the valence of the stimulus. Second, the task may elicit endogenous attention because of the predictive nature of the cue. Indeed, in the emotional spatial cueing task the peripheral cue often predicts the target location in 70% or more of the trials (e.g., Fox et al., 2001; Koster et al., 2004, 2005, Van Damme et al., 2006). Therefore, participants have an incentive to orient to the cue (Vossel, Thiel, & Fink, 2006). Consequently, it is possible that emotional processes interact with attention only after attention has been shifted exogenously or endogenously to the cued location. A third feature relates to the response mode of the task. In the emotional spatial cueing task, participants often have to localise the target and press a corresponding button (e.g., Fox et al., 2001; Koster et al., 2004, 2005, 2006, 2007; Raes et al., 2010, but see Experiment 4; Massar et al., 2011; Van Damme et al., 2004, 2006). Therefore, there is a spatial congruency between the location presentation of the target (left or right) and the respond hand (left or right). Research has shown that participants tend to respond faster when the target is spatially congruent with the response, the so-called Simon effect (Lu & Proctor, 1995; Simon & Rudell, 1967). More importantly, because in the emotional spatial cueing paradigm only one peripheral cue is presented as opposed to, for instance, two cues in dot-probe studies (MacLeod et al., 1986), the task irrelevant cue can also be spatially congruent or incongruent with the response hand. Therefore, the motor response to the target (pressing with left or right after the onset of the target) could be primed by the onset

of the cue1 (Schmidt, Haberkamp, & Schmidt, 2011). Moreover, in the modified emotional spatial cueing task the cue location is often predictive of the target location (>70%) and thus task relevant. A potential response priming effect, therefore, could even be enhanced with a predictive cue. Consequently, a threatening cue may modulate not only attentional processes but also these motor preparation processes. For instance, if a threatening cue affects motor response priming, this would result in faster responses when the threatening cue relative to a non-threatening cue is response congruent (validly cued target) and result in slower responses when the threatening cue relative to a nonthreatening cue is response incongruent (invalidly cued target). Note that these effects of emotional modulation of response priming would be similar to effects of emotional modulation of attention obtained with the emotional spatial cueing task (see for a similar argument Van Damme et al., 2008). The aim of Experiment 1 was two-folded. We wanted to investigate whether a threatening stimulus captures and holds attention exclusively due to its valence. Additionally, we wanted to investigate the time-course of attention processes in response to threat. Therefore, we adjusted the emotional spatial cueing paradigm in several ways (see Table 1). First, we used sudden onset cues that were isoluminant with the background. Table 1. The different parameters used for each experiment. In grey the critical parameters tested

Experiment

Cue validity

Cue salience

Task

1 2 3 4 5

50% 75% 50% 75% 50%

Isoluminant Isoluminant Salient Isoluminant Isoluminant

Detection Detection Detection Localization Discrimination

valid valid valid valid valid

1

Note the difference between the Simon effect, which refers to the finding that RTs are typically faster when the target is presented at the same relative location as the response, and motor response priming effects, which refers to the finding that RTs are typically faster when a prime is presented prior to the target that elicits the same motor response as the response to the target. COGNITION AND EMOTION, 2014

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Previous research has shown that isoluminant colour changes (Theeuwes, 1995), isoluminant onset cues (Lambert, Wells, & Kean, 2003; Experiments 1 and 2) or sudden onset stimuli that lack a luminance transient do not capture attention exogenously (Franconeri & Simons, 2003; but see Snowden, 2002). Second, we used a cue that was not predictive of the target location and therefore did not induce endogenous orienting. Third, participants were asked to respond to the detection of the target with one key press instead of localising the target with corresponding keys. To present threatening and non-threatening cue stimuli, we used neutral colour stimuli that were made threatening using a differential fearconditioning procedure (Mackintosh, 1983). Furthermore, we used three SOAs to investigate when in time the threatening stimulus would modulate attention. Research suggests that threatening stimuli capture attention at short SOAs (e.g., Koster et al., 2007; Öhman, Hamm, & Hugdahl, 2000) but this has not been systematically investigated with fear-conditioned colour stimuli. We expected that the threatening cue stimulus (conditioned stimulus; CS + ) would capture and hold attention, whereas the non-threatening cue stimulus (CS − ) would not. In addition, for the threatening cue stimulus (CS + ) we expected to find stronger attention effects for responses to validly cued targets at the short SOAs (50 and 100 ms) and stronger effects for responses to invalidly cued targets at the longer SOA (250 ms).

EXPERIMENT 1 Materials and methods Participants Nineteen undergraduate students (13 female, aged between 18 and 42 years) participated to fulfil course requirements. All participants gave their informed consent before participation and were free to terminate the experiment at any time. Participants had normal or corrected-to-normal vision. The study was approved by the Ghent ethics committee.

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Apparatus E-Prime software (Psychology Software Tools) was used for stimulus presentation, data recording and to control the electrocutaneous stimulation. Displays were presented on a 19-inch monitor with a resolution of 1024 × 768 pixels and a 60Hz refresh rate. Viewing distance was 55 cm. Electrocutaneous stimuli were delivered by a constant current stimulator (DIGITIMER, model DS7A), and administered to the inside of the wrist of the non-dominant forearm by two lubricated Fukuda standard Ag/AgCl electrodes (1 cm diameter). The electrocutaneous stimuli consisted of a series of 38 rectangular pulses (2 ms in duration with an inter pulse interval of 6 ms), and had a total duration of 300 ms. The experiment was conducted in a dimly lit room.

Stimuli and experiment procedure Before the experiment started, we assessed equiluminance of the red, green and gray stimuli for each participant as determined by a flicker fusion test (Ives, 1912). Subsequently, the tolerance level of the electrocutaneous stimulus was individually determined. In an intensity workup procedure participants indicated the maximum intensity of the electrocutaneous stimulus that they were willing to tolerate. This intensity was used as unconditioned stimulus (US) throughout the experiment. Next, participants started with a practice block of 16 trials. They were instructed that no USA would be given during the practice block. All stimuli were presented on a gray background (15.8 cd/m2; see Figure 1 for the basic design). A trial started with the illumination (100 ms) of the fixation cross in the middle of the screen that was presented for at least 750 ms with a random jitter of 150–250 ms. On the left and the right of the fixation cross two placeholders (8.8° × 9.3° and 17.3 cd/m2) were presented. The distance between the centre of the placeholder and the fixation cross was 10.8°. Subsequently, the cue, which consisted of an open rectangle (8.3° × 8.8°) with a width of 0.4° to avoid forward masking (Breitmeyer, 1984) was presented in the

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placeholder. The cue was either red or green and these colours were matched for luminance with the gray background of the placeholders (for each participant separately). The duration of cue presentation was either 50, 100 or 250 ms. Directly after cue presentation, the target that consisted of a small black dot (0.08°) was presented for 80 ms. Participants were asked to respond as fast as possible by pressing the spacebar with their dominant hand. The experiment consisted of three phases: the baseline phase, the acquisition phase and the experimental phase. In the first and the latter phase, six blocks were presented of 50 trials in which the cue was either valid (50%) or invalid (50%). The target could appear with equal probability on the left (50%) or the right (50%) of fixation. In each block, 20% of the trials were catch trials in which no target was presented and participants were asked to withhold their response. These trials were included to prevent participants from responding to the cue instead of the target. All trial types were presented randomly except cue duration, which was blocked. Participants were instructed that the electrocutaneous stimuli were not applied during the practice block and the baseline phase. During the acquisition phase, participants were instructed that one of the two colours would sometimes be followed by the US. They were asked not to respond to the target but to determine which colour was linked to the US. Eight trials were presented; on half of the trials the colour linked to the US (the CS + ) was presented. Half of the CS+ trials were followed by the US (partial reinforcement schedule of 50%), which was presented immediately after CS+ offset. At the end of the acquisition phase, participants had to accurately report which colour was linked to the US in order to continue the experiment. All participants indicated this correctly. During the experimental phase, participants were instructed that upon presentation of the CS+, an electrocutaneous stimulus would sometimes follow. During each block, three trials in which the CS+ was followed by the USA were added to avoid habituation and extinction of

fear (for review, see Hofmann, 2008). After the participants finished the experiment, they rated the intensity, the unpleasantness and the extent of pain experienced by the US, and the fear they felt related to the CS+ and the CS− and the extent to which they expected a US after CS+ and CS− presentation, using Likert scales on a scale from 1 (not at all) to 9 (extreme).

Results Outliers and errors Mean response error rate on the catch trials was 16.6% (min 0%, max 60.8%). A Friedman test on mean percentage error in the CS+ and the CS− during baseline phase (before conditioning) and the CS+ and CS− during the experimental phase (after conditioning) revealed a significant effect between these four conditions [X2 (3, N = 19) = 21.5, p < .01]. Two-related Wilcoxon tests showed that this effect was due to significant more errors in the CS+ condition during the experimental phase (M = 6.1%) relative to the CS+ condition during the baseline phase (M = 2.8%; z = 3.2, Nties = 4, p < .01) and relative to the CS− condition during the experimental phase (M = 4.2%; z = 2.6, N-ties = 3, p = .01). The effect between the CS− during the baseline phase (M = 3.5%) and the CS− condition during the experimental phase (M = 4.2%) was not significant (p = .15). Mean response error rate for trials on which the target was presented was low ( .16).

3 4.7 (2.1) 1.9 (1.7) 5.4 (2.1) 5.5 (1.5) 5.3 (2.1) 4.3 (1.9) 6 (1.8) 1.2 (0.4)

4 3.7 1.4 4.4 4.8 5.3 3.9 4.6 1.2

(2.1) (0.7) (2.6) (1.8) (1.8) (1.7) (1.9) (0.4)

5 3.7 1.4 4.4 4.8 5.3 3.9 4.6 1.2

To further investigate the interaction between phase and signal, we conducted separate ANOVAs for the baseline and experimental phase with SOA (50, 100, 250 ms), signal (CS+, CS − ) and cue (valid, invalid) as factors. In the baseline phase, the results showed a significant interaction between SOA and cue [F (2,36) = 9.65, p < .01, g2p = .14] due to a significant cueing effect — slower responses to validly cued targets relative to invalidly cued targets — at the 250 ms SOA [F (1,18) = 9.64, p < .01, g2p = .35] but not at the 50 and 100 ms SOA (both ps > .27). Furthermore, there was a marginal significant main effect of SOA, [F (2,36) = 3.01, p = .07, g2p = .14], no main effects of signal or cue and no interactions (all ps > .09). In the experimental phase, the results showed a main effect of SOA [F (2, 36) = 9.49, p < .01, g2p =

80 ms

50 ms, 100 ms or 250 ms

750 ms to 1000 ms

time

Figure 1. The basic design used in all five experiments. Depicted is a succession of events in a valid (or spatially congruent) trial.

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(2.1) (0.7) (2.6) (1.8) (1.8) (1.7) (1.9) (0.4)

mean reaction time (ms)

ATTENTION AND ACTION IN THE EMOTIONAL SPATIAL CUEING TASK

BASELINE

360

EXPERIMENT

360

350

350

340

340

330

330

320

320

310

310

300

300 290

290 50 ms

100 ms

50 ms

250 ms

100 ms

250 ms

SOA

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CS+

CS-

Valid

Invalid

Figure 2. Detection task. Mean reaction times in the CS+ valid condition (solid line, filled circle), CS+ invalid condition (dotted line, filled circle), the CS− valid condition (solid line, open square) and the CS − invalid condition (dotted line, open square). The left panel shows the results before fear conditioning and the right panel after fear conditioning.

.35] and a significant interaction between SOA and cue [F (2,36) = 4.46, p < .05, g2p = .2], due to a marginal significant cueing effect—slower responses to validly cued targets relative to invalidly cued targets—at the 250 ms SOA [F (1,18) = 3.86, p = .07, g2p = .18] but not at the 50 and 100 ms SOA (both ps > .15). Furthermore, as can be seen in Figure 2, there was a main effect of signal [F (1, 18) = 28.28, p < .01, g2p = .61] due to shorter reaction times after a CS+ cue relative to a CS− cue, irrespective of cue validity. All other effects were not significant (all Fs 500 ms) and did not find an overall decrease in reaction time after a threatening cue. Therefore, our results seem to reflect a general speeding induced by a threatening cue. Moreover, the error data of the catch trials seem to suggest that participants responded often to the cue instead of the target and in addition, most errors were made in the CS+ experiment condition. Therefore, shorter RTs after the threatening cue could have been induced by responses to the cue and not the target. Therefore, we re-analysed the data with only those participants who responded on less than 10% of the catch trials (N = 6). This ANOVA revealed an interaction between SOA and cue [F (2,10) = 7.63, p < .05, g2p = .6] and a marginal significant main effect of cue [F (1,5) = 5.67, p = .06, g2p = .53]. The other main effects and interactions were not significant (all ps > .11). Because our results are inconsistent with previous results from the emotional spatial cueing task, we decided to investigate whether the changes in some task parameters were responsible for this discrepancy. Therefore, we conducted the next four experiments in which we systematically COGNITION AND EMOTION, 2014

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changed one of the parameters: (1) predictive nature of the cue, (2) salience of the cue and (3) and (4) response mode.

EXPERIMENT 2 Materials and methods

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Participants Twenty-three undergraduate students (19 female, aged between 18 and 28 years) participated to fulfil course requirements. All participants gave their informed consent before participation and were free to terminate the experiment at any time. Participants had normal or corrected-to-normal vision. The study was approved by the Ghent ethics committee. Apparatus, stimuli and experiment procedure The same software and experimental set-up were used as in Experiment 1 except for the following (see also Table 1). The electrocutaneous stimuli were administered to the outside of the ankle. The cue duration was a fixed duration of 100 ms throughout the experiment. In the baseline and the experimental phase, five blocks of 40 trials were presented of which 20% were catch trials. Of particular importance in this experiment was the predictive nature of the cues. Of the target trials, 75% trials were validly cued and 25% invalidly cued. The target could appear with equal probability on the left (50%) or the right (50%) of fixation. All trial types were presented randomly. During the experimental phase, four trials in each block were added in which the CS+ was followed by the US to avoid extinction (Mackintosh, 1974).

Results Outliers and errors Mean response error rate on the catch trials was 16.9% (min 3.8%, max 63.8%). A Friedman test on mean percentage error in the CS+ and the CS−

2

during baseline phase (before conditioning), and the CS+ and CS− during the experimental phase (after conditioning) revealed a marginal significant effect between these four conditions [X2 (3, N = 23) = 7.5, p = .06]. Two-related Wilcoxon tests showed that this effect was due to significant more errors in the CS+ condition during the experimental phase (M = 5.1%) relative to the CS+ condition during the baseline phase (M = 3.6%; z = 2.2, N-ties = 3, p < .05) and relative to the CS− condition during the experimental phase (M = 3.8%; z = 2, N-ties = 7, p < .05). The effect between the CS− during the baseline phase (M = 4.4%) and the CS− condition during the experimental phase (M = 3.8%) was not significant (p = .24). Similar to Experiment 1, the error data of the catch trials seem to suggest that participants responded often to the cue instead of the target and in addition, most errors were made in the CS+ experiment condition. Therefore, we included only those participants (N = 9) in the analyses that responded on less than 10% of the catch trials2. Mean response error rate on the catch trials of these nine participants was 6.39%. There was no significant difference between the conditions (p = .27). Reaction times below 150 ms and above 1000 ms ( .22). To further investigate the interaction between phase and signal, we conducted separate ANOVAs for the baseline and experimental phase with signal (CS+, CS − ) and cue (valid, invalid) as factors. In the baseline phase, the results showed a main effect of cue [F (1,8) = 26.28, p < .01, g2p = .77]. There was no main effect of signal or an interaction between signal and cue (both ps >.08). In the experimental phase, the results showed a main effect of cue [F (1,8) = 35.23, p < .01, g2p = .82]. There was no main effect of signal or an interaction between signal and cue (both ps >.1).

Discussion The results of Experiment 2 indicate that participants oriented towards the predictive cue: responses were faster to validly cued targets relative to invalidly cued targets before and after fear conditioning. These results indicate that participants used the predictive value of the cue

and shifted attention endogenously towards the cue. However, the cue validity effect was not modulated by threat. Therefore, our hypothesis that emotion may modulate attention only after attention has been shifted endogenously to a location was not confirmed. Because the threatening cue did not modulate the cue validity effect when the cue was predictive, we decided to change one of the other task parameters. In the next experiment we used a non-predictive cue (as in Experiment 1), but the cue was now a salient visual onset cue instead of an isoluminant cue.

EXPERIMENT 3 Materials and methods Participants Twenty undergraduate students (11 female, aged between 20 and 26 years) participated to fulfil course requirements. All participants gave their informed consent before participation and were free to terminate the experiment at any time. Participants had normal or corrected-to-normal vision. The study was approved by the Ghent ethics committee. Apparatus, stimuli and experiment procedure The same software and experimental set-up were used as in Experiment 1 except for the following (see also Table 1). The cue stimulus was higher in COGNITION AND EMOTION, 2014

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Results Outliers and errors Mean response error rate on the catch trials was 16.9% (min 3.8%, max 63.8%). A Friedman test on mean percentage error in the CS+ and the CS− during baseline phase (before conditioning), and the CS+ and CS− during the experimental phase (after conditioning) revealed a significant effect between these four conditions [X2 (3, N = 20) = 8.23, p < .05]. Two-related Wilcoxon tests showed that this effect was due to a significant difference between the CS+ condition during the experimental phase (M = 3.5%) and the CS+ condition during the baseline phase (M = 2.9%; z = 2.5, N-ties = 10, p < .05). There were no differences between the CS− conditions during the experimental phase (M = baseline phase

380

mean reaction time (ms)

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luminance (± 20.1 cd/m2) than the luminance of the placeholders (17.3 cd/m2). Before the experiment started, we assessed isoluminance of the red and green cue stimuli for each participant as determined by a flicker fusion test. The cue duration was a fixed duration of 100 ms throughout the experiment. In the baseline and the experimental phase, three blocks of 40 trials were presented, of which 20% were catch trials. Of the target trials, the cue was either valid (50%) or invalid (50%). The target could appear with equal probability on the left (50%) or the right (50%) of fixation. All trial types were presented randomly.

2.3%) and the baseline phase (M = 1.5%). Similar to Experiments 1 and 2, we included only those participants (N = 13) in the analyses who responded on less than 10% of the catch trials. Mean response error rate on the catch trials of these 13 participants was 4.7%. There was no significant difference between the conditions (p = .13). Reaction times below 150 ms and above 1000 ms ( .25) were significant.

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Discussion The results of Experiment 3 indicate that participants indeed oriented towards the salient cue: responses were faster to validly cued targets relative to invalidly cued targets before and after fear conditioning. As there was no incentive for the participants to orient towards the cue (the cue was task irrelevant), these results indicate that attention was exogenously captured by the visual salient cue. However, the cue validity effect was not modulated by threat. Therefore, our hypothesis that emotion may modulate attention only after attention has been shifted exogenously to a location was not confirmed. To rule out the possibility that we did not found any attentional modulation of threat in the previous experiments because of insufficient power, we collapsed the data of the three experiments to increase power. Because there was only one SOA of 100 ms in Experiments 2 and 3, we only used the 100 ms SOA of Experiment 1. We performed an ANOVA on the reaction times with phase (baseline, experiment), signal (CS+, CS − ) and cue (valid, invalid) as within factors and experiment (non-predictive, predictive cue, salient cue) as between factor. The results revealed a main effect of cue [F (1,25) = 49.81, p < .01, g2p = .67] due to faster responses to validly cued targets relative to invalidly cued targets, which was modulated by experiment [F (1,2) = 14.58, p < .01, g2p = .54]. All other effects were not significant (all ps > .11). These results suggest that our null findings were not due to insufficient power. In the fourth experiment, we investigated whether threat could affect the motor system as discussed in the introduction. For this, we changed the detection task to a localisation task, and asked participants to respond to the location of the target with their corresponding index finger (e.g., Fox et al., 2001; Koster et al., 2004, 2005; Van Damme et al., 2004, 2006). This way, the onset cue (left or right) would prime the response to the target (left or right). We also used a predictive cue

to enhance any possible motor response priming effects. Again, we expected to find stronger cue validity effects of the threatening cue relative to the non-threatening cue after fear conditioning.

EXPERIMENT 4 Materials and methods Participants Twenty-three undergraduate students (18 female, aged between 17 and 26 years) participated to fulfil course requirements. All participants gave their informed consent before participation and were free to terminate the experiment at any time. Participants had normal or corrected-to-normal vision. The study was approved by the Ghent ethics committee. Apparatus, stimuli and experiment procedure The same software, experimental set-up, stimuli and procedure were used as in Experiment 2 except for the following (see also Table 1). Participants were asked to press with their left index finger when the target was presented on the left and with the right index finger when the target was presented on the right.

Results Outliers and errors Mean response error rate on the catch trials was 5.4% (min 0%, max 80%). There were no significant differences between the conditions. We included only those participants (N = 21) in the analyses who responded incorrectly on

Disentangling attention from action in the emotional spatial cueing task.

In the emotional spatial cueing task, a peripheral cue--either emotional or non-emotional--is presented before target onset. A stronger cue validity e...
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