Aging and the perception of 3-D shape from dynamic patterns of binocular disparity

In two experiments, we investigated the ability of younger and older observers to perceive and discriminate 3-D shape from static and dynamic patterns of binocular disparity. In both experiments, the younger observers' discrimination accuracies were 20% higher than those of the older observers. Despite this quantitative difference, in all other respects the older observers performed similarly to the younger observers. Both age groups were similarly affected by changes in the magnitude of binocular disparity, by reductions in binocular correspondence, and by increases in the speed of stereoscopic motion. In addition, observers in both age groups exhibited an advantage in performance for dynamic stereograms when the patterns of binocular disparity contained significant amounts of correspondence "noise." The process of aging does affect stereopsis, but the effects are quantitative rather than qualitative.     

Relations of Parenting and Negative Life Events to Cognitive Diatheses for Depression in Children

In a sample of 299 children (grades 2, 4, and 6), we examined parenting and negative life events as predictors of depressive cognitions, specifically low self-perceived competence, depressive cognitive schemas, and depressogenic attributional style. We also examined developmental trends in these relations. Children completed measures of parenting, negative life events, and depressive cognitions. Parents also completed measures of parenting and negative life events. Consistent with our hypotheses, negative parenting and negative life events corresponded with higher levels of depressive cognitions, whereas positive parenting corresponded with lower levels of depressive cognitions. The relations between negative parenting and negative automatic thoughts were stronger for older children. Theoretical and practical implications are discussed.     

Dishabituation in Aplysia can involve either reversal of habituation or superimposed sensitization

Dishabituation has been thought to be due either to reversal of the process of habituation or to a second process equivalent to sensitization superimposed on habituation. One way to address this question is by testing whether dishabituation and sensitization can be dissociated. Previous studies using this approach in Aplysia have come to different conclusions about the nature of dishabituation, perhaps because those studies differed in many respects, including (1) whether they also observed transient behavioral inhibition, and (2) whether they used test stimuli that activated the LE siphon sensory neurons or as yet unidentified sensory neurons. To attempt to resolve the apparent contradictions between the previous studies, we have explored the importance of these two factors by performing a parametric study of dishabituation and sensitization of gill withdrawal in a simplified preparation that does not exhibit transient behavioral inhibition, using two different test stimuli that are known to activate the LE (Touch) or unidentified (Not Touch) sensory neurons. We find that dishabituation and sensitization in this preparation have similar time courses and generally similar functions of shock intensity. However, under one condition, with the Not Touch stimulus 2.5 min after the shock, dishabituation has a reverse effect of shock intensity. Additional analyses suggest that dishabituation with the Not Touch stimulus 2.5 min after the shock is due to reversal of habituation, whereas 12.5 min after the shock, dishabituation is due to superimposed sensitization. These results thus suggest that dishabituation may involve either process in the same preparation, and begin to define the conditions that favor one or the other.     

Corpus callosum size is linked to dichotic deafness and hemisphericity, not sex or handedness

Individuals differ in the number of corpus callosum (CC) nerve fibers interconnecting their cerebral hemispheres by about threefold. Early reports suggested that males had smaller CCs than females. This was often interpreted to support the concept that the male brain is more "lateralized" or "specialized," thus accounting for presumed male predominance in mathematics, as well as for aggressive behavior. Ultimately, meta-analyses of these many reports found no significant overall sex differences in inter-cerebral information carrying capacity. Here, using quantitative MRI, we found the midline CC area of 113 subjects was significantly correlated, not with handedness or sex, but with dichotic deafness, and even more so with redefined hemisphericity, the latter accounting for over 19% of CC variability. That is, both dichotic hearing and right brain-oriented individuals of either sex had significantly larger CCs than dichotically deaf or left brain-oriented persons. Thus, current traditions of brain laterality and gender may benefit from revisions that include redefined hemisphericity.     

Executive functions and achievements in school: Shifting, updating, inhibition, and working memory

Links have recently been established between measures of educational attainment and both verbal and visuo-spatial aspects of working memory. Relationships have also been identified between specific executive functions—shifting, updating, and inhibition—and scholastic achievement. In the present study, scholastic attainment, shifting, updating, inhibition, and verbal and visuo-spatial working memory were assessed in 11- and 12-year-old children. Exploratory factor analysis identified two executive factors: one associated with updating functions and one associated with inhibition. Updating abilities were closely linked with performance on both verbal and visuo-spatial working memory span tasks. Working memory was closely linked with attainment in English and mathematics, and inhibition was associated with achievement in English, mathematics, and science. Domain-specific associations existed between verbal working memory and attainment in English, and between visuo-spatial working memory and attainment in English, mathematics and science. Implications of the findings for the theoretical analysis of executive functioning, working memory and children's learning are discussed.     

Reasons, Relevance and Salience: A Response to Hookway

This paper responds to Christopher Hookway’s article, “Reasons for Belief, Reasoning, Virtue.”     

Non-Cartesian Substance Dualism and the Problem of Mental Causation

Non-Cartesian substance dualism (NCSD) maintains that persons or selves are distinct from their organic physical bodies and any parts of those bodies. It regards persons as ‘substances’ in their own right, but does not maintain that persons are necessarily separable from their bodies, in the sense of being capable of disembodied existence. In this paper, it is urged that NCSD is better equipped than either Cartesian dualism or standard forms of physicalism to explain the possibility of mental causation. A model of mental causation adopting the NCSD perspective is proposed which, it is argued, is consistent with all that is currently known about the operations of the human central nervous system, including the brain. Physicalism, by contrast, seems ill-equipped to explain the distinctively intentional or teleological character of mental causation, because it effectively reduces all such causation to ‘blind’ physical causation at a neurological level.     

Effect of compatibility of S-R mapping on reactions toward the stimulus source

This research was concerned with separating the effects of three varieties of S-R compatibility: reactions toward the stimulus source, compatibility of S-R mapping, and display-control arrangement correspondence. In experiments 1 and 2, subjects pressed a green or red key located on the left and right in response to the onset of a green or red stimulus presented in a left or right window. Half of the subjects pressed the key which corresponded to the color of the stimulus (compatible S-R mapping) while the other half pressed the alternate colored key (incompatible S-R mapping). In the compatible mapping task, reactions were faster when location of stimulus and response corresponded than when they did not while, in the incompatible task, reactions were faster when location of stimulus and response did not correspond. This apparent reversal in the tendency to react toward the stimulus source was attributed to display- control arrangement correspondence rather than to logical recoding of the directional cue. Experiment 3 established that faster reactions toward the stimulus source occured only under compatible mapping instructions.