Genetic and environmental structure of Cloninger's temperament and character dimensions

The multivariate genetic and environmental structure of Cloninger's Temperament and Character Inventory (TCI) was investigated in a sample of 617 pairs of adolescent and young adult twins from Japan. Additive genetic factors accounted for 22% to 49% of the variability on all TCI temperament scales. Although the theory predicts lower heritability for the character scales, all character subscales had a substantial genetic contribution, and nonshared environmental influences accounted for the remainder. Multivariate genetic analyses showed that several subscales used to define one dimension shared a common genetic basis with subscales defining others. Using the degree of shared genetic influence as the basis to rearrange the TCI subscales into new dimensions, it was possible to create genetically independent scales. The implications for personality measurement, theory, and molecular genetic research are discussed.     

Leonardo's constraint: two opaque objects cannot be seen in the same direction

Given Leonardo's constraint that 2 opaque objects cannot be seen in the same direction, how are the regions of objects occluded to 1 eye included in perception? To answer this question, the authors presented 3-dimensional stimuli, similar to the ones that concerned Leonardo, and measured the visual directions of their monocular and binocular regions. When the distance between near and far objects was large, the nonfixated object was seen as double and blurry. Leonardo's constraint was met by seeing the near object as double and transparent or the distant object as double and superimposed. When the distance between near and far objects was small, the constraint was met by a perceptual displacement and compression of parts of the nonfixated object.     

A “visual” explanation of facial vision

Summary The existence of facial vision has been doubted, perhaps because of its identification with dermo-optical perception. To determine whether more credence should be granted to this alleged phenomenon, we studied both blind and sighted people. Ninety-two percent of the partially blind people reported experiencing facial vision, but only 30% of the totally blind people reported the experience. Eighty-five percent of the sighted people also reported experiencing facial vision when a shadow moved across their eyelids. In response to a questionnaire asking about subjective visual experiences, 43% of the sighted people reported seeing as though through a window on their face. The boundaries of two monocular fields mapped by apparent locations of pressure phosphenes agreed with the boundary of the area in which facial vision is experienced. The findings indicate that facial vision can be experienced by both blind and sighted persons and that it can be explained in part by the principles of visual direction.This research was supported by grant no. A0296 from the Natural Sciences and Engineering Research Council of Canada and a Canada Summer Internship Grant. The authors wish to thank S. Anstis. I. Howard, M. Komoda, M. Steinbach, N. Wade, J. Codd, and those associated with our laboratory for their helpful comments on an earlier version of this paper. The authors would also like to thank Joanne Gallagher for her help in collecting data; Milan Tytla, at the Toronto Hospital for Sick Children, for testing the blind participants; and the Canadian National Institute for the Blind, for their assistance in recruiting blind participants     

Response Stereotypy in Humans Maintained by Response-Contingent Events

The present study examined stereotyped behaviors developed during human performances that were generated by response-dependent intermittent schedules of reinforcement. Thirty university students were assigned to either fixed-interval 30-s or fixed-ratio 30-s schedules in which points or monetary reinforcers were produced only by presses on the number keys of a 41-key computer keyboard. Behavior patterns developed by all subjects were classified into four categories: optimal, random, unique, and general stereotypes. The general stereotypes category was further subdivided into five idiosyncratic types: connection, order, shift, repeat, and restriction. Analysis of the data demonstrated the role of contiguity: Whatever behavior happened to precede reinforcers was repeated even though reinforcers did not depend on that behavior. These findings support the argument that much of idiosyncratic and stereotyped human behavior is produced and maintained by contingencies of reinforcement, rather than schedule-induced or adjunctive behavior.     

Ecologically invalid monocular texture leads to longer perceptual latencies in random-dot stereograms

Two experiments were conducted to explore Gillam and Borsting's (1988, Perception 17 603-608) report that uncorrelated monocular texture facilitates stereopsis by shortening the latency to see depth in random-dot stereograms. Experiment 1 used stereograms similar, in pattern but not disparity, to Gillam and Borsting's with monocular texture present or absent. A third condition, where monocular texture was dissimilar to the binocular panels and background, was also used. We were unable to generalize the findings of Gillam and Borsting for a depth step of 6 min of arc to a larger depth step of 24 min of arc. That is, we observed no significant difference in latencies between the conditions with monocular texture absent and present at a disparity of 24 min of arc. We found latencies to be significantly longer in the monocular-texture-different condition than the monocular-texture-absent condition, however. We account for this, ad hoc, by arguing that the monocular-texture-different stereogram depicts a rare or 'accidental' visual scenario. This account was supported by the results of experiment 2 which showed that stereograms depicting accidental views yielded longer latencies than those depicting generic views. We conclude that the ecological validity of monocular texture must also be considered when assessing the effects of monocular texture on stereopsis.     

Binocular single vision achieved by fusion and suppression

The occurrences of fusion and suppression were determined from stereograms which produced two retinal images located at equal distances but in opposite directions from the fovea. Subjects reported whether the dichoptic stimulus appeared single or not, and if single whether it appeared in the center of the visual field. The report of centrality is predicted by the fusion theory of single vision and that of noncentrality by the suppression theory. Experiment 1, with eight subjects, showed that for small disparities perceived singleness was the percept predicted by the fusion theory; for larger disparities, the percepts could sometimes be predicted by the fusion theory and other times by the suppression theory. Experiment 2, with 16 subjects, showed that with larger stimuli the percept predicted by the fusion theory is more likely to occur. Experiment 3, with four subjects, showed that the centrality was reported when the stimuli were presented for 100 msec. This result provided support for our interpretation that the centrality reports in Experiments 1 and 2 were not due to fixation error and suppression.     

Apparent displacement with a monocular prism differs from optical displacement

This experiment showed that phoria-induced displacement adds to or subtracts from prism-induced displacement. A near stimulus (25 cm) was apparently displaced more than the optical displacement when the base of a prism was out and less when the base was in. In contrast, a far stimulus (200 cm) was displaced less when the base was out and more when the base was in. Moreover, the between-subjects variability of the apparent displacement was greater with monocular than with binocular viewing. Some implications for studies on monocular prism adaptation are discussed.     

The cyclopean eye vs. the sighting-dominant eye as the center of visual direction

In three experiments, competing hypotheses concerning the center of visual direction were examined with the stimuli used in the Card test which requires a subject to position the card with a hole so that a target can be seen. Each experiment used six right- and six left-sighting-eye subjects. In Experiment 1, the aperture and the target were collinear with the sighting eye. The mean apparent locations of the aperture when the target was fixated, and of the target when the aperture was fixated, were consistent with only the cyclopean-eye hypothesis; that is, the 95% confidence intervals of these means contained the predicted values from the cyclopean-eye hypothesis but not those from the sighting-eye hypothesis. In Experiment 2, subjects moved the card from the side of the nonsighting eye, and in 88% of the trials it was stopped when the nonsighting eye viewed the target. In Experiment 3, the target was viewed through the aperture with both the sighting and nonsighting eye in six different stimulus arrangements. The 95% confidence intervals of all 12 mean apparent locations of the targets contained the predicted values from the cyclopean-eye hypothesis but none of those from the sighting-eye hypothesis. These results are compatible with the cyclopean-eye hypothesis, and we therefore conclude that the sighting eye is not the center of visual direction.     

Oculomotor adjustments and size-distance perception

The relationship between perceived size and distance and oculomotor adjustments were assessed in two experiments. In both experiments, Ss were required to make scalar linear size, angular size, and distance judgments of stimuli subtending a constant retinal image size at different levels of convergence. The results of the first experiment indicate that the perceived linear size, angular size, and distance of the stimulus decreased with increased convergence, the decrease in perceived linear size being greater than that of perceived angular size. While again showing a decrease in perceived linear and angular size, the results of the second experiment also show that there was a smaller decrease in perceived distance with increased convergence when Ss continued to view the stimulus as convergence was changed than when they did not view the stimulus as convergence was changed. The implications these results have for size and distance perception are discussed.     

Substance and artifact in the higher-order factors of the Big Five

J. M. Digman (1997) proposed that the Big Five personality traits showed a higher-order structure with 2 factors he labeled alpha and beta. These factors have been alternatively interpreted as heritable components of personality or as artifacts of evaluative bias. Using structural equation modeling, the authors reanalyzed data from a cross-national twin study and from American cross-observer studies and analyzed new multimethod data from a German twin study. In all analyses, artifact models outperformed substance models by root-mean-square error of approximation criteria, but models combining both artifact and substance were slightly better. These findings suggest that the search for the biological basis of personality traits may be more profitably focused on the 5 factors themselves and their specific facets, especially in monomethod studies.