Biases in the perceived timing of perisaccadic perceptual and motor events

Subjects typically experience the temporal interval immediately following a saccade as longer than a comparable control interval. One explanation of this effect is that the brain antedates the perceptual onset of a saccade target to around the time of saccade initiation. This could explain the apparent continuity of visual perception across eye movements. This antedating account was tested in three experiments in which subjects made saccades of differing extents and then judged either the duration or the temporal order of key events. Postsaccadic stimuli underwent subjective temporal lengthening and had early perceived onsets. A temporally advanced awareness of saccade completion was also found, independently of antedating effects. These results provide convergent evidence supporting antedating and differentiating it from other temporal biases.     

Directional uncertainty in visually guided pointing

Studies of the relationship between stimulus-response uncertainty and reaction times indicate three qualitatively different functions: Hick's law, simple-choice step function, or flat curve (no effect at all). The extent of stimulus-response S-R) compatibility appears to interact with the effects of uncertainty on response times. One possible hypothesis regarding these various S-R uncertainty functions is that uncertainty will have an effect whenever the stimuli and their associated responses are not within the same egocentric spatial coordinates. We tested this hypothesis in 5 undergraduate participants (2 men, M age 18.7 yr., range 18-20) by investigating the time-course of pointing to peripherally located visual targets under four different levels of uncertainty (1, 2, 4, or 8 possible locations). Surprisingly, the resulting response function does not match any of those previously reported. Visually guided pointing produced a quadratic reaction time function as S-R uncertainty increases in log2 steps from 1 to 8.     

Endogenous testosterone concentration, mental rotation, and size of the corpus callosum in a sample of young Hungarian women

In the present study brain laterality, hemispheric communication, and mental rotation performance were examined. A sample of 33 women were tested for a possible linear relationship of testosterone level and mental rotation with structural background of the brain. Subjects with a smaller splenial area of corpus callosum tended to have lower levels of testosterone (r =.37, p<.05). However, there were no significant differences in mean scores of mental rotation of object and hand between groups with high and low levels of testosterone. There was a significant difference in relative size of the 6th area (slice) of the corpus callosum between groups with good and poor scores on mental rotation of an object and also in relative size of the 4th and 5th slices of the corpus callosum between groups on mental rotation of the hand. The good and poor scorers' show different relations with the measures of the corpus. The mental rotation of hand was associated with the parietal areas of the corpus callosum, while the mental rotation of object was associated only with the occipital area. These observations suggest that higher testosterone levels may be associated with a larger splenial area, which represents an important connection between the parieto-occipitocortical areas involved in activation of mental images. Further srudy is encouraged.     

Limited capacity for contour curvature in iconic memory

We measured the difference threshold for contour curvature in iconic memory by using the cued discrimination method. The study stimulus consisting of 2 to 6 curved contours was briefly presented in the fovea, followed by two lines as cues. Subjects discriminated the curvature of two cued curves. The cue delays were 0 msec. and 300 msec. in Exps. 1 and 2, respectively, and 50 msec. before the study offset in Exp. 3. Analysis of data from Exps. 1 and 2 showed that the Weber fraction rose monotonically with the increase in set size. Clear set-size effects indicate that iconic memory has a limited capacity. Moreover, clear set-size effect in Exp. 3 indicates that perception itself has a limited capacity. Larger set-size effects in Exp. 1 than in Exp. 3 suggest that iconic memory after perceptual process has limited capacity. These properties of iconic memory at threshold level are contradictory to the traditional view that iconic memory has a high capacity both at suprathreshold and categorical levels.     

Contingent muscular tension during a choice reaction task

This study examined the effects of contingent muscular tension on a choice reaction task, and especially, the effects various amounts of muscular tension have on the information processing of choice reaction time. The reactive movement task included a choice reaction task. Ten right-handed healthy men (ages 18 to 19 years) underwent trials with stimulus presentation probabilities of 50% and 20% on the muscular tension task and choice reaction tasks. The conditions for the muscular tension tasks were divided into seven different conditions: 0%, 10%, 20%, 30%, 40%, 50%, and 60% of maximum voluntary contraction. On these tasks, subjects performed isometric contraction of the biceps brachii. The choice reaction task was a rapid extension of the left or right knee as a choice reaction. Measures were choice reaction time, movement time, and total reaction time. Analysis indicated that shortening choice reaction time of the left and right feet was observed under 10% muscular tension of maximum strength. Muscular tension appreciably influenced information processing, including choice reaction time. Muscular tension did not affect movement time. Results are discussed with respect to previous research and the optimal muscular tension for best performance.     

Smiling faces rated more feminine than serious faces in Japan

It has been reported that women and girls smile more frequently and more effectively than men and boys. It is expected that this correlation between femaleness and smiling affects the processing of faces, and consequently, smiling faces may be perceived to be more feminine. Participants viewed 30 photographs featuring smiling and serious facial expressions of both male and female subjects and rated them for femininity or masculinity. The result indicated that smiling faces significantly more frequently gave the impression of being more feminine. The interaction between the sex of the faces and their expression was not significant.     

Effects of the orientation of moving objects on the perception of streaming/bouncing motion displays

In this study, we examined the contribution of the orientation of moving objects to perception of a streaming/bouncing motion display. In three experiments, participants reported which of the two types of motion, streaming or bouncing, they perceived. The following independent variables were used: orientation differences between Gabor micropatterns (Gabors) and their path of motion (all the experiments) and the presence/absence of a transient tone (Experiment 1), transient visual flash (Experiment 2), or concurrent secondary task (Experiment 3) at the coincidence of Gabors. The results showed that the events at coincidence generally biased responses toward the perception of bouncing. On the other hand, alignment of Gabors with their motion axes significantly reduced the frequency of bounce perception. The results also indicated that an object whose orientation was parallel to its motion path strengthened the spatiotemporal integration of local motion signals along a straight motion path, resulting in the perception of streaming. We suggest that the effect of collinearity between Gabors and their motion path is relatively free from the effect of attention distraction.     

Dichotic listening with forced attention in patients with temporal lobe epilepsy: significance of left hemisphere cognitive dysfunction

Fifty right-handed patients with focal temporal lobe epilepsy were administered a dichotic listening test with consonant-vowel syllables under non-forced, forced right and forced left attention conditions, and a neuropsychological test battery. Dichotic listening performance was compared in subgroups with and without left hemisphere cognitive dysfunction, measured by the test battery, and in subgroups with left and right temporal epileptic focus. Left hemisphere cognitive dysfunction led to more correct responses to left ear stimuli in all three attention conditions, and fewer correct responses to right ear stimuli in the non-forced attention condition. This was probably caused by basic left hemisphere perceptual dysfunction. Dichotic listening was less affected by a left-sided epileptic focus than by left hemisphere cognitive dysfunction. General cognitive functioning influenced dichotic listening performance stronger in forced than in non-forced attention conditions. Larger cerebral networks were probably involved in the forced attention conditions due to the emphasis on conscious effort.     

Children of divorce in a Scandinavian welfare state: Are they less affected than US children?

A fairly common view holds that children's risks of negative outcomes associated with family dissolution are generally small or even nonexistent in Scandinavia, and clearly smaller than what is usually found in the United States. This view was empirically examined in a recent large-scale study of 4,127 12–15-year-old children in Norway, of whom 623 had experienced parental divorce and lived in a single-mother family. The somewhat paradoxical pattern of findings was as follows: (a) The negative associations between parental divorce and various outcomes were found to be generally very similar in Norway and the United States in spite of the great differences in family policy and welfare benefits for single mothers (at the macro level); and (b) Mediational effects of family economic resources were in both countries most marked for the academic achievement area, and the predictive power of such variables was quite similar, again in spite of the great differences in absolute level of the economic resources available to single-mother families in the two countries. The results cast some doubt on the value of the absolute economic deprivation perspective in explaining the results, and the many Norwegian welfare benefits do not seem to mitigate the association between divorce and negative outcomes for the children involved. Also policy implications derived from the economic deprivation perspective are questioned. Alternative interpretations of the findings involving relative deprivation and economic resources as a partial proxy for other non-economic factors are briefly discussed.     

Online Story Comprehension among Children with ADHD: Which Core Deficits are Involved?

Children with ADHD have difficulty understanding causal connections and goal plans within stories. This study examined mediators of group differences in story narrations between children ages 7-9 with and without ADHD, including as potential mediators both the core deficits of ADHD (i.e., inattention, disinhibition, planning/working memory) as well measures of phonological processing and verbal skills. Forty-nine children with ADHD and 67 non-referred children narrated a wordless book and completed tasks assessing the core deficits of ADHD, phonological processing, and verbal skills. Results revealed that, although no shorter than those of non-referred children, the narratives of children with ADHD contained fewer elements relating to the story's causal structure and goal plan. Deficits in sustained attention accounted for the most variance in these differences. Results have implications for understanding and ameliorating the academic problems experienced by children with ADHD.