Biomedical subjects
Publications and source records attributed to D T Lykken.
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New methods for examining eye movements were developed and applied in a study of young, adult monozygotic twins. Subjects, tested twice, engaged in smooth pursuit tracking at different target frequencies, followed a stimulus requiring saccadic eye movements, performed a related psychomotor hand tracking task, and tracked a target while monitoring changes in the stimulus display. Analysis of test-retest reliability and twin concordance suggested that performance on these tasks characterized stable traits and were consistent with other reports implicating a genetic contribution to tracking ability. Special consideration was given to the probable role of attention in producing various types of tracking deficit. Estimates of the incidence of tracking dysfunction and correlations with psychometrically measured personality traits were examined.
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A lack of agreement exists among studies of electrodermal habituation in schizophrenia. One explanation for the intractable discrepancies observed concerns the likelihood that there exists intersubject variability in the significance patients attach to stimuli. This possibility is encouraged through the administration of vague and uninformative instructions. A more controlled and sensible procedure, which allows habituation to be measured with greater ecological validity, involves providing subjects with an absorbing alternative task on which to focus their attention after being specifically instructed to ignore the habituation stimulus to the best of their ability.
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Uniovular and diovular twin pairs can be classified with at least 90% accuracy by careful questioning or by ratings by observers of similarity in appearance, eye color, ear conformation, and the like. This article outlines the methods required for highly accurate zygosity diagnosis using blood typing, fingerprints, and anthropometry. The logic behind the use of discrete Mendelian phenotypes is explained and tables are provided which give the odds against a dizygotic twin pair showing concordance on eight blood group systems, four serum proteins, and six red blood cell enzymes. These tables are suitable for use with American twins of European ancestry; the method of generating such tables is explained so that similar tables based on different gene frequency estimates or for additional genetic markers can be easily constructed. The logic behind the use of metric, polygenic traits in zygosity diagnosis is also presented, together with tables giving the odds against a dizygotic twin pair showing various degrees of similarity in ponderal index, in cephalic index, and in Slater's Z score, a measure of fingerprint similarity. Taken together, the 18 serological markers should misclassify dizygotic twins as monozygotic fewer than two times in 1000. With the three anthropometric variables, this average probability of misclassification drops about 1 order of magnitude.
The warned foreperiod reaction time (RT) task is claimed to provide data supportive of the Laceys' visceral afferent feedback theory. However, although there are many reports of significant between-subject correlations between heart rate (HR) and RT, more direct tests examining within-subject covariation show, at best, inconclusive results. These studies suggested several procedural refinements which could produce stronger within-subject relationships. The procedures adopted in this investigation included manipulating attentional involvement by varying imperative stimulus (IS) intensity, using a respiratory control and a repeated measures design, recording electromyographic RT, employing a contact switch manipulandum with no moving parts, and having subjects initiate trial presentation. 40 males were divided between normal breathing and hold breath groups. Subjects received three blocks of 24 trials with the IS at either 10, 50, or 80 db. A variety of measurement and statistical approaches yielded generally negative results, with an overall mean within-subject correlation in the predicted direction of -0.06.
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