Perception of gaze direction based on luminance ratio

Changing the luminance of one side of the sclera induces an apparent shift of the perceived direction of gaze toward the darker side of the sclera (Ando, 2002 Perception 31 657-674). However, when both the sclera and the skin surrounding it were darkened simultaneously as if by a cast shadow, the apparent direction of gaze shifted less than when only the sclera was darkened. The results suggest that one mechanism for gaze judgment is based on a simple analysis of the local luminance ratio between the eye and the surrounding region.     

Asymmetric recognition of pictures of cats as a function of age in 4-, 5-, and 6-year-old children

In the present study it was investigated whether children recognized deletions more accurately than additions in pictures of animate objects as a function of age between 4 and 6 years. Children, presented pictures of cats with features added to or deleted from the original pictures, judged whether the pictures were the same or different as those in a test of recognition. Analysis showed both 5-yr.-olds and 6-yr.olds discovered deletions more accurately than additions. This asymmetric effect is in accord with that of adults, with whom the same stimuli were used in earlier research, but are contrary to previous studies in which additions were recognized more accurately than deletions when inanimate objects were stimuli. Asymmetric effects, that is, greater recognition accuracy for deletions may be related to children's being uncomfortable about modified pictures of animals.     

Eye contact does not facilitate detection in children with autism

Eye contact is crucial in achieving social communication. Deviant patterns of eye contact behavior are found in individuals with autism, who suffer from severe social and communicative deficits. This study used a visual oddball paradigm to investigate whether children with high functioning autism have difficulty in detecting mutual gaze under experimental conditions. The results revealed that children with autism were no better at detecting direct gaze than at detecting averted gaze, which is unlike normal children. This suggests that whereas typically developing children have the ability to detect direct gaze, children with autism do not. This might result in altered eye-contact behavior, which hampers subsequent development of social and communicative skills.     

Cultural variations on optimistic and pessimistic bias for self versus a sibling: is there evidence for self-enhancement in the west and for self-criticism in the east when the referent group is specified?

A culturally relevant framework was used to examine variations on optimistic and pessimistic bias in Westerners and Easterners. Study 1 showed that 136 European Americans compared with 159 Japanese were more likely to predict typical positive events to occur to self than to a sibling. The opposite pattern emerged in the prediction of typical negative events. Study 2 replicated these findings on the basis of predictions for atypical events in 175 European Americans and 130 Japanese. Across both studies, within-groups analyses indicated that European Americans held an optimistic bias in the prediction of positive and negative events, whereas Japanese held a pessimistic bias for negative events. These findings are taken to offer support for presumed cultural differences in self-enhancement and self-criticism between Westerners and Easterners, respectively.     

Binocular rivalry alternation rate declines with age

The effect of aging on the time of spontaneous perceptual alternation in binocular rivalry was examined in 59 subjects. An earlier study reported the change of alternation time by comparing middle-age and elderly subjects. We also observed age-related prolongation in alternation time by comparing subjects in a lower age group (20-34 years) with those in both a middle-age group (35-49 years) and a higher age group (50-64 years). Aging of visual optical functions such as presbyopia or the reduction of contrast sensitivity has an accelerating effect over age and may not be related to the age-associated monotonic prolongation of alternation time in binocular rivalry. The origin of aging in binocular rivalry is still unclear but a neural interval generator for perceptual switching is suggested.     

Textural properties corresponding to visual perception based on the correlation mechanism in the visual system

We present a set of texture parameters that correspond to perceptual properties of visual texture. For machine vision or a computer interface, it is important that the computational measurements of texture correspond well to the perceptual properties. To understand the mechanism of our visual system, it is important to know how we extract or characterize information for texture perception. In this study, we show that the autocorrelation function (ACF) analysis provides useful measures for representing three salient perceptual properties of texture: contrast, coarseness, and regularity. The validity of the ACF analysis was examined by comparing the calculated factors to the subjective scores collected for various kinds of natural textures. The effectiveness of the analysis depends on the structure of the estimated ACF. When a texture has a harmonic structure, the estimated ACF has periodical peaks corresponding to the periods of the texture. Both perceived coarseness and regularity are strongly related to these peaks in the ACF. However, the estimated ACF does not have a periodical structure when the texture is random. In this case, the texture coarseness and regularity are represented by the decay rate of the ACF.     

Conditioned taste aversion learning in leptin-receptor-deficient db/db mice

The db/db mouse has defective leptin receptors. The defects lead to impairments of leptin regulation of food intake and body weight, and result in the expression of diabetic symptoms such as hyperinsulinemia, hyperglicemia, and extreme obesity. Recent studies have proposed that leptin may also affect memory and learning processes. To examine this possibility, we compared the ability of leptin-receptor-deficient db/db mice and their normal lean litter mates to form and extinguish a conditioned taste aversion (CTA) for saccharin. We used a short-term (10 s) lick test and a long-term (48 h) two bottle preference test for measurement of consumption of test solutions. On the first day after conditioning to avoid saccharin, the db/db mice showed preference scores for saccharin as low, and aversion thresholds for sucrose lower than that of the lean mice. During the extinction test trials beginning from the second up to the 30th day after conditioning, numbers of licks and preference scores for aversive saccharin and sucrose appeared to be larger, and recovered faster to the control levels in db/db mice. These results indicate that db/db mice with leptin-receptor-deficiency may show equal capacity to form CTAs for saccharin, greater generalization from saccharin to sucrose, and a faster rate of extinction. This suggests that disruption of leptin signalling does not inhibit acquisition of CTA learning, but impairs its extinction. This differential contribution of the leptin system on CTA processes may be due to differential distribution of leptin receptors in the CTA-related brain areas.     

The missing fundamental phenomenon in temporal vision

Subjective flicker rates were measured for compound waveforms consisting of five harmonics without a fundamental component. It was found that observers perceived a rate at the fundamental frequency, although energy at this frequency was not included in the signals. In auditory pitch sensation this is called the missing fundamental phenomenon, and an analogous finding is known to occur in spatial vision. Moreover, observers perceived the flicker rates at the fundamental frequency even in the random-phase conditions, in which the period of the fundamental component is unclear in the real waveforms. The results indicate that the perceived flicker rates are not detected from the temporal waveforms per se. One possible mechanism for extracting such a periodicity in the signal is an autocorrelation function to the real temporal waveforms. Received: 18 October 1999 / Accepted: 28 January 2000     

Bidirectional influences between maternal parenting and children's peer problems: a longitudinal monozygotic twin difference study

This twin study examined the bidirectional relationship between maternal parenting behaviors and children's peer problems that were not confounded by genetic and family environmental factors. Mothers of 259 monozygotic twin pairs reported parenting behaviors and peer problems when twins were 42 and 48 months. Path analyses on monozygotic twin difference scores revealed that authoritative parenting (the presence of consistent discipline and lack of harsh parenting) and peer problems simultaneously influenced each other. Authoritative parenting reduced peer problems, and peer problems increased authoritative parenting. Neither consistent discipline nor harsh parenting alone was associated with peer problems. These results suggest that maternal authoritative parenting works protectively in regard to children's peer problems, and peer problems can evoke such effective parenting.