Temporal factors in the discrimination of coherent motion

When observers view the relative movements of a pair of bars defined by the difference of spatial Gaussian functions (DOGs), they can accurately discriminate coherent movements over a range of temporal frequencies and temporal asynchronies. Of particular interest is the fact that performance accuracy is maintained even when the two bars differ in spatial-frequency content and contrast. On each trial, observers viewed two brief presentation intervals in which a pair of vertically oriented DOGs moved randomly back and forth within a restricted range. During one observation interval, both elements moved in the same direction and by the same magnitude (correlated), and in the other interval, the movements were independent (uncorrelated). Temporal asynchronies were introduced by delaying the displacement of the right bar relative to that of the left bar in each interval. Observers were able to discriminate correlated versus uncorrelated movements up to a 45–60-msec temporal delay between the two elements’ relative displacements. If motion processing is accomplished by mechanisms operating over multiple spatial and temporal scales, the visual system’s tolerance of temporal delays among correlated signals may facilitate their space-time integration, thereby capitalizing on the perceptual utility of coherent-motion information for image segmentation and interpolating surface structure from the movements of spatially separated features.     

Thematic analysis in agrammatic comprehension: syntactic structures and task demands.

Aphasics' ability to assign thematic roles during sentence comprehension was investigated. The study was motivated by the hypothesis that capacity limitations, e.g., due to slowed processing operations, interact systematically with certain aspects of structural analysis more than with others. Experiments using a sentence-picture matching paradigm were conducted with several agrammatic Broca's and paragrammatic Wernicke's patients. Experiment 1 tested comprehension of various syntatic structures. The astoundingly good performance in Experiment 1 for both patient groups was attributed to the low task demands of the experiment. Raising the task demands, by delaying presentation of the relevant picture set in Experiment 2, resulted in a significant decrement of comprehension performance for agrammatic Broca's aphasics, but not for Wernicke's aphasics. Putting the main verb in the sentence-final position, as in Experiment 3, affected Wernicke's aphasics', but not Broca's aphasics' performance. In principle, one explanation for the performance differences between Experiments 1 and 2 for Broca's patient might be a deficit in these patients' verbal memory capacity. Therefore, verbal memory span on different word categories was tested in an additional experiment. No difference, however, was found between the Broca's patients' and the Wernicke's patients' capacity for verbal memory despite their different sentence comprehension profiles. The present data are taken to support the view that Broca's aphasics' comprehension behavior is due to the processing demands imposed by structural inference chains and not to a general reduction in verbal memory.     

Judgments of moving and intending to move in a timed-response task

Summary Subjects performed a timed-response task in which they attempted to synchronize a rapid flexion of the index finger of their preferred hand with the last of a train of four regularly spaced acoustic clicks. The task was used to stabilize the execution time of a simple voluntary response in order to facilitate psychophysical judgments about the subjects' perception of having responded and of having intended to respond. In the first experiment, male subjects (N = 6) adjusted the appearance time of a reference stimulus (a brief percutaneous pulse to the responding finger) until it appeared to be simultaneous with their perception of having made the response. All subjects adjusted the reference stimulus to appear after response onset during the latter half of the force impulse. This finding suggests that the perception of having responded is based on peripheral feedback from the response. In the second experiment, male subjects (N = 6) performed the same motor task, but adjusted the time of the reference stimulus so that it appeared to be simultaneous with their intention to respond. Two subjects were not able to do the task successfully; the remaining four subjects adjusted the reference stimulus to appear from 101 to 145 ms before response onset. This finding suggests that the intention to respond is perceptually separable from the response itself and occurs at a measurable time before response onset.     

On deriving the properties of agrammatic comprehension

Several recent studies characterize agrammatic comprehension as a computational rather than a conceptual deficit. A restriction in the computational capacity of the processor may affect sentence comprehension performance unevenly due to the varying demands imposed by different sentence structures and different tasks. It is argued that structures involving longer inferential chains suffer greater degradation than structures involving shorter inferential chains. Many of the observed properties of agrammatic comprehension may be seen to follow from this principle alone.     

Diagnosing behavior-disordered early adolescents as a function of cultural differences

The tendency of non-Indian teachers to rate American Indian early adolescents (11-year olds) as behaviorally disordered more frequently than similarly behaving non-Indian children is examined. To test this hypothesis, the observed number of students rated as behavior-disordered by non-Indian teachers were compared with the expected number. A chi-square test revealed no significant tendency for this pattern to occur chi 2 = 2.04 less than .05, df = 1).     

Conceptual implicit memory: A developmental study

The widely accepted standpoint that implicit memory emerges earlier in development than explicit memory, and is more stable from childhood to adult age, is based on experimental data essentially collected in perceptual tasks. The present study was aimed at investigating whether these findings still hold when a more conceptual task is used. We compared the performance of children at two age levels (2nd and 4th grades) on a category-exemplar generation task. Results showed that performances of the two groups were comparable when the target items were typical of their categories, as in Experiment 2, and for a subset of the items in Experiment 1. However, the older children outperformed the younger children in Experiment 1 when the items selected were atypical of their categories. Interpretations of these findings are discussed.Preparation of this article was supported by the Centre National de la Recherche Scientifique (URA CNRS 316 and 1838), the Université de Bourgogne, and the Université René-Descartes     

The role of pragmatic principles in resolving attachment ambiguities: Evidence from eye movements

In an eyetracking experiment, participants read sentences that contained a prepositional phrase (PP) that could be attached to one of two preceding verbs. To understand the sentence, readers had to select which verb would serve as the host for the PP. In some of the sentences, the critical verbs and the PPs were part of a subordinate clause in which lexical and syntactic factors were expected to matter, but discourse factors favoring attachment of the material to positions where it would be relevant to the main assertion of the sentence were not expected to matter. In other sentences, the critical material was tested in main clause contexts in which the main assertion principle was predicted to apply. Hierarchical linear modeling showed that online attachment preferences were affected by clause type (main vs. subordinate). Specifically, the preference for a local verb over a distant verb was greater when the critical material appeared within a subordinate clause than when it appeared within a main clause. This pattern of results can be explained by the operation of the relativized relevance or main assertion principle, which in our sentences meant that participants favored attachment of the PP to the first verb over the second.     

Fighting like a girl fighting like a guy: gender identity, ideology, and girls at early adolescence

In this chapter we explore the phenomenon of "girls fighting like guys" by listening to adolescent girls' justification for physical fighting with other girls. We argue that physical girlfighting is a particular kind of gendered performance--a performance of identity that expresses, at least in part, an answer to the question, "Who am I?"--that both perpetuates and challenges the usual notions of masculinity and femininity and the differential power associated with these discourses. We present a sociocultural approach to identity that we believe not only holds promise for helping us to understand girl-fighting behavior but also highlights the clear interrelationship between social identity and personal identity. We conclude by highlighting several implications of this analysis for those who work with girls (and boys) in educational and clinical settings.     

Developmental changes in judgments of authentic objects

This study examined the development of an understanding of authenticity among 112 children (preschoolers, kindergarten, 1st graders, and 4th graders) and 119 college students. Participants were presented with pairs of photographs depicting authentic and non-authentic objects and asked to pick which one belongs in a museum and which one they would want to have. Results suggest that both children and adults recognize the special nature of authentic objects by reporting that they belong in a museum. However, this belief broadens with age, at first just for famous associations (preschool), then also for original creations (kindergarten), and finally for personal associations as well (4th grade). At all ages, an object's authentic nature is distinct from its desirability. Thus, from an early age, children appear to understand that the historical path of an authentic object affects its nature. This work demonstrates the importance of non-obvious properties in children's concepts. For preschool as well as older children, history (a non-visible property) adds meaning beyond the material or functional worth of an object.