Neuropsyclmlogia,1976,Vol. 14,pp.261to 264. PergamonPress. Printed in England.
NOTE HANDEDNESS
ASSESSMENT
INVENTORY
K. WHITE and R. ASHTON Department
of Psychology, University of Queensland, (Received
St. Lucia, Queensland 4067, Australia
16 July 1975)
Abstract-A modified form of Oldfields Edinburgh Handedness Inventory was given to 406 students. The results obtained were subjected to factor analysis. This analysis revealed the presence of two factors; one which could be labelled handedness and a smaller one which was dependent upon the wording of items. It was speculated that the latter factor may be associated with the respondent’s ability to manipulate mental images.
INTRODUCTION THE hand preference of subjects employed in studies of hemispheric specialization of function is usually assessed by handedness inventories or questionnaires. This is a necessary first step in such experiments, because left handers have uncertain specializations, SUSIRANA[l] refers to them as having bicerebrality. Most experimenters, therefore, employ only right-handed subjects. There are many pencil and paper tests (see TOUWEN [2]for a list of some popular ones), but no investigator has, to date, produced any evidence that such tests are valid. Thus the tests possess only face validity and handedness is defined solely in terms of test scores. The above comments apply to what is probably the most widely used test; OLDFIELD'S [3]Edinburgh Handedness Inventorv. Oldfield uroduced very extensive data on the distribution of scores on this test. The question remains, however, as to whether his data represent test scores or handedness distribution in his large sample, there being no evidence presented that they were the same thing. The present paper represents an attempt to examine the structure of a modified version of the Edinburgh Handedness Inventory; to assess the correlations between individual questions, between individual questions and the total score, and, finally, to assess the factorial structure of this test. In terms of the latter analysis the predicted outcome was, obviously, that the test would show a single major factor of “handedness”.
METHOD We studied the scores of 406 test-unsophisticated Introductory Psychology students on a modified form of Handedness Inventory. The major modifications made to the original test were the dropping of some items which Australian students had difficulty in interpreting, the addition of replacement items and a change in the scoring procedure to be used by the respondents. This latter modification replaced Oldfield’s use of i-, -t + responses with a line divided into 5 parts next to each question. The students had to indicate the strength of their preference for one hand or the other by ticking the appropriate division of the line. This checking procedure simplified extraction of numerical data for statistical analysis. The test was administered to students in groups varying in size from 10 to 50. The test was one in a booklet containing several unrelated questionnaires. OLDRELD'S [3] Edinburgh
RESULTS The mean checked score per item and the overall mean score for the whole 18 items with their associated standard deviations, are given in Table 1. Intercorrelations between the 19 scores (18 questions and one total score) were then Pearson’s Product moment method. (To save space, these results will not be given here, request from the authors.) The intercorrelation matrix showed that all questions were both to each other and to the total score. 261
in the test, together computed using the but are available on significantly related,
NOTE
262
Table 1. Means and standard deviations of checked responses on a modified form of Oldfield’s Edinburgh Handedness Inventory (N = 406) _-_
_____
5 Xean
4.16
Standard Deviation
L.32
G
73
Xe an
4.67
11.22
Standard Ceviation
L.O!!
1.37
Question :I
L
::UIII~EF
1”
13
14
140an
3.87
.4.5c
3.93
4.72
Standard Deviation
1.06
1.14
?.29
0.92
:
17
18
c) r
‘.‘otal Score
; :ean
4.49
L.38
4.27
79.39
Standard Cnvi atIon
1.09
1.3,;
1.1:
- L.96
Table 2. Factor loadings on the handedness
Percent variance. unrotated analys:s Percent variance; ‘Jarimax rotated
analysis
questionnaire obtained after principal components rotation procedures
56.45
,6.23
and varimax
NOTE
263
The intercorrelations between the 18 questions were then examined further using factor analytic techniques. (The total score part of the matrix was not included in these analyses, because, being a derived score, inclusion would have tended to favour a factor pattern with an extremely large general factor.) The data were initially factored by a principal components analysis. Applying the GWTMAN [4] and KAISER[5] criterion than one should only consider factors with latent roots greater than unity only two factors were retained for Varimax rotation [6]. The variance accounted for by these factors is given in Table 2. The loadings of each question obtained after the factor analyses are shown in Table 3. The factor patterns obtained by the two procedures were so simple and similar that it was unnecessary to go further in our analysis. Table 3. Factor loadings on each question of the Handedness irinciple
Coiqonents
Analysis
*‘actor
3
F _I
1.0
>
1.
12
13 14 15 16 17 18
1
.84 .66 .75 .02 .58 .87 .74 .77 .76 .69 .61 .84 .54 .a4 .87 .81 .59 .81
Varinax
Inventory
Rotation
Analysis
Factor
2
.35 .O5 -15 .ll .46
.31 -05 .24 .06 .28 .39
.08 .52 .26 SO7 .O7 .06 .02
Factor
.89
.58 .71 .74 .22 .90 .59 .50 .66 .41 .28 .74 .15 .a4 .76 .71 .46 .66
1
Factor 2
.18 -33 .29 -37 .7O .23 .46 .63 .38 .62 .66 -40 .73 .25 .43 .39 .38 . 4’7
DISCUSSION The analyses described above demonstrate that the present questionnaire has a simple factorial structure. There was one major factor which could legitimately be called “handedness”. The other minor factor extracted was probably an artifact resulting from the wording of several questions. To expand, the factor loadings of each question (Table 3) show that the deviant questions, those loading highly on this second factor, were all items demanding a response for the non-preferred hand. To give a “correct” answer to these questions would have demanded some thought on the part of the respondents. It is interesting to speculate that this taking of thought (to coin Eccle’s phrase) may have involved some mental imagery by the students; they had to imagine carrying out the task in order to arrive at the correct answer. This speculation is in need of further study. Acknowledgement-This
research was supported
by grant A73115077 from the ARGC.
REFERENCES 1. SUBIRANA,A. Handedness and cerebral dominance. Handbook clin. Neurol. 4, 248-272, 2. TOUWEN,B. C. L. Laterality and dominance. Cerebr. Palsy. Bull. 14, 747-755, 1972.
1969.
NOI E
264
OLDFIELD,R. C. The assessment and analysis of handedness:
The Edinburgh
Inventory.
Neuropsycho-
logia9,97-113,197l.
GUTTMAN,L. Some necessary conditions for common-factor analysis. Psychometrika 19,149-161, 1954. of electronic computers to factor analysis. Educ. psychol. Measur. 20, 141-151,196O. KAISER,H. F. The Varimax criterion for analytic notation in factor analyses. Psychomefrika 23,187-200, 1958.
KAISER, R. The application
Deutschsprachige
Zusammenfassung:
Eine modifizierte tar wurde 406
Form van Oidfield's
Studenten
vorgelegt.
Faktox.enanalyse unterzogen. bedeutungsvoll
Edinturp~r
"Y:ljiekeitr.lr::~~!,--
Die !IcsultcLe h-:~.:lz~: ei:;ri'
Llie Analyse
ergab, da13 2 h'~kro~'._~;
sind: Einer der ~1s "HBndigkeitsfaktor"
werden konnte und ein geringerer,
ctiky-';.tiert
der van der Eezcichnung
de:
"Items" abhing. Es wurde vermutet, dail dar letztere Faktor mit der FUhigkoit der jeweilig Untersushten rusammer;h#ngen kSnnte, eigene Vorstellungen
zu handhaben.
NOTE HANDEDNESS
ASSESSMENT
INVENTORY
K. WHITE and R. ASHTON Department
of Psychology, University of Queensland, (Received
St. Lucia, Queensland 4067, Australia
16 July 1975)
Abstract-A modified form of Oldfields Edinburgh Handedness Inventory was given to 406 students. The results obtained were subjected to factor analysis. This analysis revealed the presence of two factors; one which could be labelled handedness and a smaller one which was dependent upon the wording of items. It was speculated that the latter factor may be associated with the respondent’s ability to manipulate mental images.
INTRODUCTION THE hand preference of subjects employed in studies of hemispheric specialization of function is usually assessed by handedness inventories or questionnaires. This is a necessary first step in such experiments, because left handers have uncertain specializations, SUSIRANA[l] refers to them as having bicerebrality. Most experimenters, therefore, employ only right-handed subjects. There are many pencil and paper tests (see TOUWEN [2]for a list of some popular ones), but no investigator has, to date, produced any evidence that such tests are valid. Thus the tests possess only face validity and handedness is defined solely in terms of test scores. The above comments apply to what is probably the most widely used test; OLDFIELD'S [3]Edinburgh Handedness Inventorv. Oldfield uroduced very extensive data on the distribution of scores on this test. The question remains, however, as to whether his data represent test scores or handedness distribution in his large sample, there being no evidence presented that they were the same thing. The present paper represents an attempt to examine the structure of a modified version of the Edinburgh Handedness Inventory; to assess the correlations between individual questions, between individual questions and the total score, and, finally, to assess the factorial structure of this test. In terms of the latter analysis the predicted outcome was, obviously, that the test would show a single major factor of “handedness”.
METHOD We studied the scores of 406 test-unsophisticated Introductory Psychology students on a modified form of Handedness Inventory. The major modifications made to the original test were the dropping of some items which Australian students had difficulty in interpreting, the addition of replacement items and a change in the scoring procedure to be used by the respondents. This latter modification replaced Oldfield’s use of i-, -t + responses with a line divided into 5 parts next to each question. The students had to indicate the strength of their preference for one hand or the other by ticking the appropriate division of the line. This checking procedure simplified extraction of numerical data for statistical analysis. The test was administered to students in groups varying in size from 10 to 50. The test was one in a booklet containing several unrelated questionnaires. OLDRELD'S [3] Edinburgh
RESULTS The mean checked score per item and the overall mean score for the whole 18 items with their associated standard deviations, are given in Table 1. Intercorrelations between the 19 scores (18 questions and one total score) were then Pearson’s Product moment method. (To save space, these results will not be given here, request from the authors.) The intercorrelation matrix showed that all questions were both to each other and to the total score. 261
in the test, together computed using the but are available on significantly related,
NOTE
262
Table 1. Means and standard deviations of checked responses on a modified form of Oldfield’s Edinburgh Handedness Inventory (N = 406) _-_
_____
5 Xean
4.16
Standard Deviation
L.32
G
73
Xe an
4.67
11.22
Standard Ceviation
L.O!!
1.37
Question :I
L
::UIII~EF
1”
13
14
140an
3.87
.4.5c
3.93
4.72
Standard Deviation
1.06
1.14
?.29
0.92
:
17
18
c) r
‘.‘otal Score
; :ean
4.49
L.38
4.27
79.39
Standard Cnvi atIon
1.09
1.3,;
1.1:
- L.96
Table 2. Factor loadings on the handedness
Percent variance. unrotated analys:s Percent variance; ‘Jarimax rotated
analysis
questionnaire obtained after principal components rotation procedures
56.45
,6.23
and varimax
NOTE
263
The intercorrelations between the 18 questions were then examined further using factor analytic techniques. (The total score part of the matrix was not included in these analyses, because, being a derived score, inclusion would have tended to favour a factor pattern with an extremely large general factor.) The data were initially factored by a principal components analysis. Applying the GWTMAN [4] and KAISER[5] criterion than one should only consider factors with latent roots greater than unity only two factors were retained for Varimax rotation [6]. The variance accounted for by these factors is given in Table 2. The loadings of each question obtained after the factor analyses are shown in Table 3. The factor patterns obtained by the two procedures were so simple and similar that it was unnecessary to go further in our analysis. Table 3. Factor loadings on each question of the Handedness irinciple
Coiqonents
Analysis
*‘actor
3
F _I
1.0
>
1.
12
13 14 15 16 17 18
1
.84 .66 .75 .02 .58 .87 .74 .77 .76 .69 .61 .84 .54 .a4 .87 .81 .59 .81
Varinax
Inventory
Rotation
Analysis
Factor
2
.35 .O5 -15 .ll .46
.31 -05 .24 .06 .28 .39
.08 .52 .26 SO7 .O7 .06 .02
Factor
.89
.58 .71 .74 .22 .90 .59 .50 .66 .41 .28 .74 .15 .a4 .76 .71 .46 .66
1
Factor 2
.18 -33 .29 -37 .7O .23 .46 .63 .38 .62 .66 -40 .73 .25 .43 .39 .38 . 4’7
DISCUSSION The analyses described above demonstrate that the present questionnaire has a simple factorial structure. There was one major factor which could legitimately be called “handedness”. The other minor factor extracted was probably an artifact resulting from the wording of several questions. To expand, the factor loadings of each question (Table 3) show that the deviant questions, those loading highly on this second factor, were all items demanding a response for the non-preferred hand. To give a “correct” answer to these questions would have demanded some thought on the part of the respondents. It is interesting to speculate that this taking of thought (to coin Eccle’s phrase) may have involved some mental imagery by the students; they had to imagine carrying out the task in order to arrive at the correct answer. This speculation is in need of further study. Acknowledgement-This
research was supported
by grant A73115077 from the ARGC.
REFERENCES 1. SUBIRANA,A. Handedness and cerebral dominance. Handbook clin. Neurol. 4, 248-272, 2. TOUWEN,B. C. L. Laterality and dominance. Cerebr. Palsy. Bull. 14, 747-755, 1972.
1969.
NOI E
264
OLDFIELD,R. C. The assessment and analysis of handedness:
The Edinburgh
Inventory.
Neuropsycho-
logia9,97-113,197l.
GUTTMAN,L. Some necessary conditions for common-factor analysis. Psychometrika 19,149-161, 1954. of electronic computers to factor analysis. Educ. psychol. Measur. 20, 141-151,196O. KAISER,H. F. The Varimax criterion for analytic notation in factor analyses. Psychomefrika 23,187-200, 1958.
KAISER, R. The application
Deutschsprachige
Zusammenfassung:
Eine modifizierte tar wurde 406
Form van Oidfield's
Studenten
vorgelegt.
Faktox.enanalyse unterzogen. bedeutungsvoll
Edinturp~r
"Y:ljiekeitr.lr::~~!,--
Die !IcsultcLe h-:~.:lz~: ei:;ri'
Llie Analyse
ergab, da13 2 h'~kro~'._~;
sind: Einer der ~1s "HBndigkeitsfaktor"
werden konnte und ein geringerer,
ctiky-';.tiert
der van der Eezcichnung
de:
"Items" abhing. Es wurde vermutet, dail dar letztere Faktor mit der FUhigkoit der jeweilig Untersushten rusammer;h#ngen kSnnte, eigene Vorstellungen
zu handhaben.
