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Biomedical subjects

D K Detterman

Publications and source records attributed to D K Detterman.

15 recordsLinked to original sources
PubMed1995

The genetic and environmental variance underlying elementary cognitive tasks.

Although previous studies have examined the genetic and environmental influences upon general intelligence and specific cognitive abilities in school-age children, few studies have examined elementary cognitive tasks in this population. The current study included 149 MZ and 138 same-sex DZ twin pairs who participated in the Western Reserve Twin Project. Thirty measures from the Cognitive Abilities Test (CAT; Detterman, 1986) were studied. Results indicate that (1) these measures are reliable indicators of general intelligence in children and (2) the structure of genetic and environmental influences varies across measures. These results not only indicate that elementary cognitive tasks display heterogeneous genetic and environmental effects, but also may demonstrate that individual differences in biologically based processes are not necessarily due to genetic variance.

Adolescent↗
PubMed1992

Assessment of basic cognitive abilities in relation to cognitive deficits.

A modal model of information-processing was used to select a battery of nine tasks of basic cognitive ability (learning, relearning, reaction time, probe recall, Sternberg search, self-paced probe, stimulus discrimination, tachistoscopic full report, tachistoscopic partial report). Parameters from these tasks operationalized the model. After extensive pilot testing of the tasks to establish reliability, we tested 40 subjects (20 with mental retardation and 20 college students) on all tasks and the WAIS-R. The parameters from the tasks were generally reliable (.7 through .9) and had low correlations with IQ (average about .37). Nearly all of the major cognitive parameters differentiated significantly between groups. A subset of the basic cognitive parameters predicted IQ with an estimated multiple correlation in the general population of .72. Prediction of IQ using basic cognitive parameters was better for subjects with mental retardation than for college students. A modified version of the modal model was supported. Results show that individual differences in higher mental processes are highly dependent on basic cognitive abilities and can be predicted from them. These findings have substantial implications for the development of models of information-processing.

Adolescent↗
PubMed1990

Differences in heritability across groups differing in ability.

Differences in heritability and environmentality were assessed for 54 DZ and 86 MZ same-sex twin pairs between 6 and 12 years of age from the Western Reserve Twin Project. A principal-component score composed of the subtests of the WISC-R, PPVT, WRAT, and MAT represented each twin's cognitive ability. Using a modification of a regression technique developed by DeFries and Fulker (1985), it was possible to assess differential heritability and environmentality across ability level. A number of variants of this procedure were used and all yielded the same result: lower ability subjects show higher heritabilities and lower shared environmentality. This result is attributable to larger differences between DZ twins at low ability levels and to differences between MZ twins, which are either the same across ability level or are smaller at low ability levels. A possible explanation for this effect is a genotype-environment correlation in which higher-ability persons seek out better environments. The results from this study should be regarded as tentative but the methods used can be applied to other twins studies. Investigators should be aware of the importance of representing the low end of the distribution in their samples.

Achievement↗
PubMed1990

Effect of instructions on elementary cognitive tasks sensitive to individual differences.

The effect of instructions on basic cognitive tasks was investigated. In the first study, 60 college students completed both a choice reaction time and a modified match-to-sample task. Students were given either written, non-verbal, or no instructions. Mean level of performance changed across type of instruction for each task. The correlations between the task parameters and a measure of general intelligence also appeared to change across instructional conditions. A second study was conducted with 464 Air Force and National Guard recruits who completed choice reaction time, match-to-sample, tachistoscopic threshold, and probed recall tasks. Approximately half of these subjects received standard written instructions while the others received no instructions. Mean group differences were substantial but decreased with practice. Patterns of individual differences between the instruction and no-instruction conditions varied more with increased task complexity, with greater change occurring in more complex tasks such as probed recall. In sum, instructions have a significant impact on mean performance on basic cognitive tasks and a lesser effect on individual differences.

Adult↗
PubMed1988

Is it smart to play the horses? Comment on "A day at the races: a study of IQ, expertise, and cognitive complexity" (Ceci & Liker, 1986).

Ceci and Liker (1986b) presented data that they contended shows two things: (a) Handicapping harness races is a cognitively complex undertaking that can be captured by a multiple regression model, and (b) neither overall skill at handicapping nor the complexity of the mental model used is related to standard measures of intelligence. The first contention is not at issue. But the second contention, that handicapping performance is unrelated to IQ, is not supported by the data presented; in fact, the opposite conclusion seems more likely. The purpose of this comment is to point out errors frequently made in individual-differences research concerning population definition, sample selection, dependent and independent variable reliability and validity and interpretation of results.

Cognition↗
PubMed1987

Information-processing correlates of computer-assisted word learning by mentally retarded students.

Information-processing correlates of computer-assisted word learning by moderately and severely mentally retarded students were identified. Nineteen subjects completed 10, 15-minute computer-assisted instruction sessions and seven basic cognitive tasks measuring simple learning, choice reaction time, relearning, probed recall, stimulus discrimination, tachistoscopic threshold, and recognition memory. Stimulus discrimination, probed recall, and simple learning were significantly related to word learning. Results suggest that instruction should be modified to accommodate individual differences in these abilities.

Adolescent↗
PubMed1987

Theoretical notions of intelligence and mental retardation.

A theory of the cause of mental retardation that views human intelligence as a set of independent abilities organized in a complex system was presented. Mental retardation is conceived as a deficit in a few of the independent abilities having high centrality (i.e., processes most important in system functioning). Abilities affected and severity of impairment vary across individuals. Besides making specific predictions that allow rejection, the theory can be used to account for differences between Ellis's deficit theory and Zigler's developmental theory of mental retardation.

Human Development↗
PubMed1983

Stimulus encoding by mentally retarded and nonretarded adults.

Stimulus encoding was studied with a group of mentally retarded and nonretarded adults. Two sets of 24 nonverbal stimuli were selected; one had a wide range of stimulus structure variables and the other, a representative sample of stimuli. Performance on a match-to-sample task for both stimulus sets was assessed and correlated with the stimulus structure of the standard stimulus. Although there were significant group differences in speed of matching or encoding, matching times for retarded and nonretarded subjects for each stimulus were correlated .97 and .90 for each stimulus set. Correlations of matching times with the stimulus structure variables for each stimulus were very similar for both subject groups. We concluded that both groups encode stimuli in similar ways, but at different rates.

Adult↗
PubMed1981

Performance of mentally retarded and nonretarded persons on a lifted-weight task with strategies reduced or eliminated.

To test the hypothesis that a strategy deficit entirely accounts for retarded persons' inferior short-term memory performance, we attempted to eliminate strategies by selecting a task in which strategies would be difficult to use (memory for the position of a lifted weight) and by having subjects report the use of any strategy. In Experiment 1, discriminability among lifted weights was roughly equated for retarded and nonretarded subjects. Experiment 2 showed that for subjects not reporting use of a strategy, nonretarded subjects performed better than did retarded subjects. Use of a strategy improved the performance of nonretarded and retarded subjects by the same amount. In Experiment 3, a task was devised that made it nearly impossible to use the strategies that had been reported in Experiment 2. This increased the reported use of strategies in both groups, though strategies did not significantly improve performance. Thus, the report of strategies used in Experiments 2 and 3 was negatively related to their effectiveness. Findings of Experiment 2 and 3 suggest that a strategy deficit is not sufficient to account for the memory deficit displayed by retarded subjects.

Adult↗
PubMed1975

The von Restorff effect and induced amnesia: production by manipulation of sound intensity.

When an outstanding item appears in an otherwise homogeneous list of items, the outstanding item is better remembered (the von Restorff effect), and items before and after it may be more poorly remembered (induced amnesia) than corresponding items in a control list. In the present experiments the outstanding item was a word presented as a loud shout among other words presented at normal conversational levels. In two experiments, large retrograde- and anterograde-induced amnesiae effects were demonstrated using a free-recall and a recognition task. In both experiments half of the subjects were told what to expect and were instructed to devise a strategy to eliminate induced amnesia. These instructions failed to eliminate the amnesiac effect. A third experiment was designed to demonstrate an empirical similarity between induced and clinical amnesia. In clinical retrograde (but not anterograde) amnesia, "lost" memories are sometimes recovered with time. Filled delays of 0, 30, or 120 sec interpolated between list presentation and recall demonstrated that induced retrograde amnesia disappeared at the longest delay but induced anterograde amnesia was unchanged. A fourth experiment eliminated some alternate interpretations of the effect.

Adult↗