Perceptual and Motor Skills, 1977,45,694.
@ Perceptual and Motor Skills 1977
RELIABILITY OF A MEASURE OF VISUAL IMAGERY1 JOSEPH S. ROSSIa Uniz~ersityo f Rhode Island The resurgence of interest in visual imagery has generated a number of studies concerned with the reliability of tests purporting to measure the ability to form visual images. Typically results have shown such tests to be internally consistent but not impressively reliable over time. However, only a few studies have investigated the reliability of Marks' ( 1 ) Vividness of Visual Imagery Questionnaire, which has been shown to be effective in predicting recall of both verbal ( 3 ) and pictorial material ( 1 ) . Odd/even and test-retest reliabilities of 0.85 and 0.74, respectively ( I ) , of 0.93 and 0.67, respectively (.2 ,) ., have been found. This seems to indicate that a transient "state" is being- measured by imagery tests rather than a more stable "trait." Present results challenge this interpretation. Initial testing was carried out on 119 students enrolled in introductory psychology. An unannounced second administration, for which 88 of the original subjects were present, took place 7 wk. later. Mean score on the questionnaire for the first administration was 2.31 ( S D = 0.75) and for the second administration 2.39 ( S D = 0.79). Odd/even reliability, stepped up by the Spearman-Brown formula, was 0.94 for the first administration and 0.96 for the second administration of the test. Test-retest reliability was 0.73. These results seem consistent with previous reliabilities of imagery questionnaires. However, inspection of the scatterplot of test vs retest scores showed that three subjects were greatly out of line with the remaining 85 subjects. Recalculation of the test-retest reliability without these three subjects yielded a coefficient of 0.87. Such results suggest that the ability to form visual images may actually be quite stable for most subjects and ephemeral for only a few. A principal components analysis was also performed for each administration of the test. A single general component accounted for 42% of the variance for the first administration and 52% of the test variance for the second administration of the test. All items loaded .50 or higher at each session with a mean loading of .65 (SD = .08) for the first administration and of .72 ( S D = .06) for the second. Coefficient alpha was 0.91 for the first session and 0.94 for the second. The high values of alpha, as well as the finding that a single general component accounted for approximately 50% of the test variance, suggest that the Vividness of Visual Imagery Questionnaire is a reasonably pure measure of the ability to form visual images. These results, along with the finding that the test is highly reliable over time for most subjects, suggest that imagery may be a stable trait and that the questionnaire may be a useful instrument with which to measure individual differences in the ability to form visual images REFERENCES 1. MARKS,D. F. Visual imagery differences in the recall of pictures. British Journal o/ Psychology, 1973, 64, 17-24. P. P. Reliability of two measures of visual imagery. 2. MCKKLVIE,S. J., & GINGRAS, Perceptual and Motor Skills, 1974, 39, 417-418. 3. R o s s ~ J. , S., & FINGERET,A. L. Individual differences in verbal and imagery abilities: paired-associate recall as a function of stimulus and response concreteness. Perceptual and Motor Skills, 1977, 44, 1043-1049. Accepted August 29, 1977. 'Thanks are due W. Velicer for helpful comments. 'Requests for reprints should be sent to Joseph S. Rossi, Department of Psychology, Chafee Social Science Center, University of Rhode Island, Kingston, R. I. 02881.
@ Perceptual and Motor Skills 1977
RELIABILITY OF A MEASURE OF VISUAL IMAGERY1 JOSEPH S. ROSSIa Uniz~ersityo f Rhode Island The resurgence of interest in visual imagery has generated a number of studies concerned with the reliability of tests purporting to measure the ability to form visual images. Typically results have shown such tests to be internally consistent but not impressively reliable over time. However, only a few studies have investigated the reliability of Marks' ( 1 ) Vividness of Visual Imagery Questionnaire, which has been shown to be effective in predicting recall of both verbal ( 3 ) and pictorial material ( 1 ) . Odd/even and test-retest reliabilities of 0.85 and 0.74, respectively ( I ) , of 0.93 and 0.67, respectively (.2 ,) ., have been found. This seems to indicate that a transient "state" is being- measured by imagery tests rather than a more stable "trait." Present results challenge this interpretation. Initial testing was carried out on 119 students enrolled in introductory psychology. An unannounced second administration, for which 88 of the original subjects were present, took place 7 wk. later. Mean score on the questionnaire for the first administration was 2.31 ( S D = 0.75) and for the second administration 2.39 ( S D = 0.79). Odd/even reliability, stepped up by the Spearman-Brown formula, was 0.94 for the first administration and 0.96 for the second administration of the test. Test-retest reliability was 0.73. These results seem consistent with previous reliabilities of imagery questionnaires. However, inspection of the scatterplot of test vs retest scores showed that three subjects were greatly out of line with the remaining 85 subjects. Recalculation of the test-retest reliability without these three subjects yielded a coefficient of 0.87. Such results suggest that the ability to form visual images may actually be quite stable for most subjects and ephemeral for only a few. A principal components analysis was also performed for each administration of the test. A single general component accounted for 42% of the variance for the first administration and 52% of the test variance for the second administration of the test. All items loaded .50 or higher at each session with a mean loading of .65 (SD = .08) for the first administration and of .72 ( S D = .06) for the second. Coefficient alpha was 0.91 for the first session and 0.94 for the second. The high values of alpha, as well as the finding that a single general component accounted for approximately 50% of the test variance, suggest that the Vividness of Visual Imagery Questionnaire is a reasonably pure measure of the ability to form visual images. These results, along with the finding that the test is highly reliable over time for most subjects, suggest that imagery may be a stable trait and that the questionnaire may be a useful instrument with which to measure individual differences in the ability to form visual images REFERENCES 1. MARKS,D. F. Visual imagery differences in the recall of pictures. British Journal o/ Psychology, 1973, 64, 17-24. P. P. Reliability of two measures of visual imagery. 2. MCKKLVIE,S. J., & GINGRAS, Perceptual and Motor Skills, 1974, 39, 417-418. 3. R o s s ~ J. , S., & FINGERET,A. L. Individual differences in verbal and imagery abilities: paired-associate recall as a function of stimulus and response concreteness. Perceptual and Motor Skills, 1977, 44, 1043-1049. Accepted August 29, 1977. 'Thanks are due W. Velicer for helpful comments. 'Requests for reprints should be sent to Joseph S. Rossi, Department of Psychology, Chafee Social Science Center, University of Rhode Island, Kingston, R. I. 02881.
