Five experiments used a new response-duration measure in explorations of the conditions necessary for confirmation of Hick's law. Hick's law states that reaction time increases logarithmically with number of choices. Exceptions to the law, venerable as it is, have been reported. They have always included the following conditions: a verbal response; a familiar stimulus with a single dominant name; and a large number of practice trials. These conditions have carried a heavy explanatory burden in accounting for the anamolous results. The present studies use none of these conditions and yet manage to replicate the anamolous result of a very shallow slope across set size, a slope less than one-tenth the usual value. This was accomplished by using a novel task in which the initial component of the response is the same for all stimuli (depression of a single response key) but the termination of the response is different (different durations for each stimulus). Using this task, a slope in the neighborhood of 15 ms per bit of stimulus uncertainty is found, as compared with the usual value of about 150 ms. A number of possible explanations are examined. Among the most important are the possibilities that response overlap is the critical factor (i.e., duration errors overlap); possible stimuli are simply ignored when more than one is involved; and the duration decision is made after the reaction-time interval rather than during it. All three possibilities, as well as some others, are found to be inconsistent with the various experimental outcomes. Instead, a new theory of choice reaction time is presented, which emphasizes the nature of the S-R code that is assumed to represent various reaction-time tasks. This theory leads to a new "law" that is put forward as a replacement for Hick's law. It is RT = a + b(1 - N-1).
The purpose of this study was to measure the separate contributions of maternal IQ and home environment as they predict child IQ. Both parental IQ and child IQ were measured with Raven's Standard Progressive Matrices and the Peabody Picture Vocabulary Test. These tests were adminstered to 80 mothers, 35 fathers, and 80 children (mean age 12 years). Home intellectual environment was assessed through a 2-hour interview with the mother. Multiple regression analyses showed that for each IQ test and for the two scores combined, the addition of home environment ratings to the regression equations did not add a significant increment to the prediction of child IQ from that provided by maternal IQ, whereas the addition of maternal IQ to the regression equation did add a significant increment to that provided by home environment ratings. Thus it was clearly demonstrated that the correlation of home environment and child IQ is considerably overestimated when maternal IQ is allowed to covary. When maternal IQ was statistically controlled, the correlation between home environment ratings and child IQ was attenuated to nonsignificance.The major goal of this study was to assess the relative influences of maternal intelligence and home environment on the intelligence of the child. There are few studies that have measured these two influences independently. Instead, the usual procedure is to measure only home environment (and indirectly at that) by simply obtaining an index of socioeconomic status (SES) and determining the relationship between parental SES and child IQ. The typical correlation is around .40. Vernon (1979) described the typical conclusion:It is usually taken for granted by most American psychologists that the superior IQs of upper-and middle-We thank Paul Games, Arthur R. Jensen, Lee Willerman, and two anonymous referees for their comments on an earlier version of this article. We would also like to express appreciation to Longstreth's entire class of Intellectual Development, Spring 1979, for its involvement in planning and preliminary interviewing. The class members were
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