Comments on John B. Carroll's “how shall we study individual differences in cognitive abilities?—Methodological and theoretical perspectives”

A critique by Carroll (1978) of a study by Jarman and Das (1977) is discussed in terms of the methodology and theory of the Jarman and Das study. Additionally, two general issues concerned with individual differences in cognitive processes, and strategic behavior, are elaborated beyond Carroll's discussion. It is suggested that the Carroll critique of the Jarman and Das research is incorrect in several respects, and the theory on which this research was based may contribute some needed conceptual and operational distinctions to future individual differences investigations.     

Suprathreshold binocular interactions for grating patterns

Binocular interactions of suprathreshold grating patterns have been investigated using a reaction time measure of contrast detection. Simple reaction times were determined for monocular and binocular viewing conditions over a contrast range from .63 to near threshold. The results from all subjects showed binocular summation for contrast levels near threshold, but there was considerable variation across subjects for contrast levels above threshold. Some subjects showed summation over the entire contrast range, but other subjects showed either binocular inhibition or binocular facilitation for some range of contrast levels. The pattern of binocular interaction for a given subject was consistent for several spatial frequencies. The differences in types of interaction between subjects, the variation in magnitude of binocular interaction with contrast level for each subject, and the data from experiments involving stimulation of noncorresponding retinal areas show that the binocular interactions found for suprathreshold stimuli cannot be accounted for on the basis of probability, and must, therefore, result from physiological interactions between the two eyes. These interactions have been investigated further under conditions of (1) induced fixation disparity, (2) horizontal gratings, and (3) orthogonally oriented gratings.     

Common items and reliability in personality measurement

Most psychological tests and inventories, particularly in personality and attitude measurement, contain common items, that is, various subscales of the test or inventory may share one or more items in common. Surprisingly, the role of common items in such a fundamental personality test attribute as reliability is not known. The present report specifically considered common-item contributions to test internal consistency reliability using extant data from the California Psychological Inventory. No negative contribution of item overlap was found. To the contrary, it was concluded that the use of common items is an economical technique for increasing the total number of items in the scales, thus increasing scale internal reliabilities without increasing the overall number of items in the inventory.     

The dilution effect: Nondiagnostic information weakens the implications of diagnostic information

In a series of studies, subjects were asked to make predictions about target individuals. Some subjects were given information about the target which pretest subjects had judged to be “diagnostic”—that is, had judged to be usefully predictive of the outcome. Other subjects were given a mix of information judged to be diagnostic and information judged to be “nondiagnostic” by pretest subjects—that is, judged to be of little value for predicting the outcome. Subjects given mixed information made much less extreme predictions than did subjects given only diagnostic information. It was argued that this “dilution effect” occurs because people make predictions by making simple similarity judgments. That is, they compare the information they have about the target with their conception of outcome categories. The presence of individuating but nondiagnostic information about the target reduces the similarity between the target and those outcomes that are suggested by the diagnostic information. One of the major implications is that stereotypes and other “social knowledge structures” may be applied primarily to abstract, undifferentiated individuals and groups and may be largely set aside when judgments are made about concrete, individuated people.     

Self-instructions: Effects of cognitive level and active rehearsal

This research examined the effects of a self-instruction intervention on the relationship between cognitive level and conceptual tempo. Preoperational and concrete operational children received the Matching Familiar Figures Test prior to and after serving in either a no training control group, a content only control group, or a self-instruction group. Children in the content only control group received the same set of self-guiding strategy statements as those in the self-instruction group but without overt rehearsal of the statements. Cognitive level and conceptual tempo were strongly related; preoperational children tended to be classified as impulsive, concrete operational chidlren, as reflective. Although cognitive level predicted overall performance, with concrete operational children being more successful and more reflective than preoperational children, the influence of training was similar for both groups. On posttest, children in the self-instruction groups made more correct responses and were more reflective than children in the other two training groups.     

Evaluation of the relative effectiveness of methylphenidate and cognitive behavior modification in the treatment of kindergarten-aged hyperactive children

This study of kindergarten-aged hyperactive children evaluated the effects of three modes of treatment in relation to an untreated control group. The treatments were administered over a 3-month period and included cognitive behavior modification, methylphenidate, and the two treatments combined. A follow-up assessment was done approximately 1 year later at the end of the first grade. Analyses of psychological, rating scale observational, and interview data showed that hyperactive children became less symptomatic over time;the data did not provide evidence indicating that any of the treatments studied was more effective than any other or than no treatment at all.This research was supported by grants from the Ontario Mental Health Foundation (Grant No. 701-76/78) and The Hospital for Sick Children Foundation (Grant No. 77-22). The authors wish to thank Mr. Syl Sauro, of the Etobicoke Board of Education, and Mrs. M. Stijovic, of the Etobicoke Community Health Department, for their cooperation.