Frequency estimation in verbal learning

A multicopy theory of frequency estimation and discrimination is applied to some data found in the literature on verbal learning. The main theoretical assumption adopted is that ‘relevant’ copies generated during study have to be discriminated from ‘irrelevant’ copies as are available in memory from other occasions than the study session proper. At retrieval, copies of either type are added and their sum determines the frequency estimates that are actually reported. A formalization of these ideas is presented and applied to Hinztman's (1969) and Underwood, Zimmerman, and Freund's (1971) data. Two specific models that emphasize either storage or retrieval of copy information are studied. The results show that the models provide a close approximation to the frequency discrimination data. With absolute frequency estimation, both the means and standard deviations of the judgements are predicted reasonably well. However, some reservations were dictated by the fact that, in one instance, the tails of the judgement distributions were not accounted for. The theory offers a theoretical framework for Underwood et al.'s method of cross-relating absolute frequency and forced choice judgements; the usefulness of two approaches to this problem is established. Also, possible extensions of the theory are noted.     

Emeralds are no chameleons — Why “Grue” is not projectible for induction

The model function for induction of Goodmans's composite predicate Grue was examined by analysis. Two subpredicates were found, each containing two further predicates which are mutually exclusive (green and blue, observed before and after t). The rules for the inductive processing of composite predicates were studied with the more familiar predicate blellow (blue and yellow) for violets and primroses. The following rules for induction were violated by processing grue: From two subpredicates only one (blue after t) appears in the conclusion. As a statement about a future and unobserved condition this subpredicate, however, is not projectible for induction whereas the only suitable predicate (green before t) does not show up in the conclusion. In a disjunction a v b where a is true and b false the disjunction is true. When, however, the only true component is dropped, what remains is necessarily false. An analogous mistake may be observed in the processing of grue, where the only true component (green) was dropped in the conclusion. — As a potent criterion for correct inductions a check of the necessity of the conclusions is recommended.The author is indebted to Prof. Curt Christian for valuable suggestions.     

Spatial navigation in complex and radial mazes in APP23 animals and neurotrophin signaling as a biological marker of early impairment

Impairment of hippocampal function precedes frontal and parietal cortex impairment in human Alzheimer's disease (AD). Neurotrophins are critical for behavioral performance and neuronal survival in AD. We used complex and radial mazes to assess spatial orientation and learning in wild-type and B6-Tg(ThylAPP)23Sdz (APP23) animals, a transgenic mouse model of AD. We also assessed brain content of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3). Performance was alike in wild-type and APP23 animals in the radial maze. In contrast, performance in the complex maze was better in wild-type than APP23 animals. Contrary to the wild-type, hippocampal BDNF levels decreased on training in APP23 animals. Hippocampal and frontal cortex NGF levels in APP23 animals correlated with the time to solve the complex maze, but correlated inversely with escape time in wild-type animals. NT-3 levels were alike in wild-type and APP23 animals and were unchanged even after training. Both types of mazes depend on hippocampal integrity to some extent. However, according to the cognitive mapping theory of spatial learning, the complex maze because of the increased complexity of the environment most likely depends more strongly on preserved hippocampal function than the radial maze in the working memory configuration applied here. Greater impairment in complex maze performance than in radial maze performance thus resembles the predominant affliction of the loss of hippocampal function in human AD. NGF and BDNF levels on maze learning are different in wild-type and transgenic animals, indicating that biological markers of AD may be altered on challenge even though equilibrium levels are alike.     

Task preparation and stimulus-evoked competition

The authors investigated how task competition evoked by a stimulus that affords both a currently relevant and a temporarily irrelevant task is affected by invalid preparation, i.e., preparation for the irrelevant task. Although invalid preparation was associated with a general performance cost, effects of stimulus-cued task competition were not enhanced on invalidly prepared trials. This result suggests that either preparation activates representations different from the ones by which stimulus cuing is mediated or that stimulus processing is postponed until invalid preparation has been corrected. In addition, invalid preparation resulted in impaired performance of the respective task when it became relevant on a subsequent trial. This result is consistent with the idea that competition due to invalid preparation is countered by task-specific inhibition.     

Thin slices of behavior as cues of personality and intelligence

Self-reports, peer reports, intelligence tests, and ratings of personality and intelligence from 15 videotaped episodes were collected for 600 participants. The average cross-situational consistency of trait impressions across the 15 episodes was .43. Shared stereotypes related to gender and age were mostly accurate and contributed little to agreement among judges. Agreement was limited mainly by nonshared meaning systems and by nonoverlapping information. Personality inferences from thin slices of behavior were significantly associated with reports by knowledgeable informants. This association became stronger when more episodes were included, but gains in prediction were low beyond 6 episodes. Inferences of intelligence from thin slices of behavior strongly predicted intelligence test scores. A particularly strong single predictor was how persons read short sentences.     

Sociability and positive emotionality: genetic and environmental contributions to the covariation between different facets of extraversion

The relation between sociability and positive affect is one of the most often replicated results of research on personality and subjective well-being. It is shown how behavior genetics can contribute to our understanding of the covariance between sociability and positive emotionality. The results of a multimethod behavior-genetic study with 158 monozygotic and 120 dizygotic twins are reported. In this study, sociability and two components of positive emotionality (positive affect, energy) were assessed by self-report and other report. Additionally, positive state affect was assessed in five situations and aggregated across situations. The results showed that there are strong genetic correlations between all variables. Furthermore, there are substantive correlations between the nonshared environmental components of the different variables. Shared environmental influences, however, seemed to be unimportant for explaining the correlations between sociability and the different components of positive emotionality. The results are discussed with respect to their implications for future research on sociability and positive emotionality.     

Gender differences on the WPPSI,the WISC-R,and the WPPSI-R

The WPPSI, WISC-R, and WPPSI-R were administered in a counterbalanced design to 72 children between the ages of 5 years, 10 months, 16 days, and 6 years, 7 months, and 15 days to test the hypothesis that mean verbal IQs on these scales would be higher for boys than for girls. Results indicated that the mean verbal IQs for boys were significantly (p<.05) higher than those for girls on all three scales. Also, significant (p<.05) differences favoring boys were found onVocabulary andComprehension subtests on all three scales. These differences are probably a peculiarity of these scales and may not need any elaborate theoretical explanation. However, clinical uses of verbal and performance IQ discrepancies may not justifiably ignore the examinees’ gender.