Correction processes in early reaching: Reaches by infants to prismatically displaced targets

Summary A comparison was made between trajectories of reaches to visual targets by 6-months-old infants, with and without lateral prismatic displacement. In the No Prism condition, the major element of the movement veered towards the target, confirming the results of Mathew and Cook (1990). In the Prism condition, the prism did not affect hand position or movement direction at the beginning of the major element, but a lateral displacement was evident by the end of the element. This is taken as evidence that shifts in trajectory during the element were not due to visual guidance. It is suggested instead that these shifts may reflect correction based upon somatic feedback about position in relation to the visually specified goal of the movement. Evidence that the hand approached the virtual target supports the suggestion that any visual guidance was confined to the approach phase of the reach. Nevertheless, it appears that visual guidance was operating at this stage, since movement direction was displaced away from the virtual target and towards the real target.     

The utility of verbal and behavioral assessments of value.

Subjects lived in a laboratory apartment for up to 30 days, engaging in ordinary activities such as reading, sewing, and artwork. The amount of time devoted to each activity was recorded and compared with periodic verbal ratings of the amount of time devoted to the activities. The verbal and observational assessments of the time distribution were very similar, but there were some discrepancies. Based on self-reports and on observation of time actually devoted to the activities, contingencies were arranged in which time devoted to one activity produced time available for a second activity. When the contingency relation was based on behavioral assessment, predictions of time redistribution were more accurate than when the relations were based on verbal assessment. The close correspondence between observed distributions of time and verbally assessed distributions was probably due to the well-specified situation and rigorous assessment methods. Contrary to some cognitive-behavioral accounts, the contingency results suggest that verbal assessment is not necessarily preferable to observation when the two make discrepant predictions. It is suggested that verbal reports might be used more often in behavior analysis in place of lengthy or difficult observations, and attention is drawn to a personality model that parallels important components of behavior analysis.     

Choice with Concurrent Interval Schedules of Reinforcement: The Effects of Different Timing Procedures

Using a Findley changeover procedure, two groups of rats were exposed to various concurrent variable-time (VT) schedules of milk presentation. The rules governing the operation of the timers for the stimulus events differed for the two groups with resulting differences in the overall degree of changeover responding but not with respect to time allocation measures, which in both cases consisted of undermatching. When an interrupted VT reinforcement timer was reset upon re-entry of that component, the rats tended to emit changeover responses almost exclusively to the more favorable component. When the VT reinforcement timers were left running regardless of which components the rats selected, changeover responses were significantly more frequent and equally distributed among both the more and less favorable components. In comparing the present results with those from a similar procedure in which shock was used (Deluty & Church, 1978), it is apparent that what is basic to choice in concurrent interval schedules is not matching or some mathematical variation of it. Instead, it is a tendency to optimize on the basis of the favorability of the stimulus events and the contingencies regarding how those events are timed and administered.

     

A Piagetian perspective on mathematical construction

In this paper, we offer a Piagetian perspective on the construction of the logico-mathematical schemas which embody our knowledge of logic and mathematics. Logico-mathematical entities are tied to the subject's activities, yet are so constructed by reflective abstraction that they result from sensorimotor experience only via the construction of intermediate schemas of increasing abstraction. The ‘axiom set’ does not exhaust the cognitive structure (schema network) which the mathematician thus acquires. We thus view ‘truth’ not as something to be defined within the closed ‘world’ of a formal system but rather in terms of the schema network within which the formal system is embedded. We differ from Piaget in that we see mathematical knowledge as based on social processes of mutual verification which provide an external drive to any ‘necessary dynamic’ of reflective abstraction within the individual. From this perspective, we argue that axiom schemas tied to a preferred interpretation may provide a necessary intermediate stage of reflective abstraction en route to acquisition of the ability to use formal systems in abstracto.     

Converging operations on a basic level in event taxonomies

Research on object concepts has identified one level of abstraction as "basic" in cognition and communication. We investigated whether concepts for routine social events have a basic level by replicating the converging operations used to investigate object concepts. In Experiment 1, subjects were presented with event names from a taxonomy and were asked to list the actions comprising the event. Many more actions were listed at the middle than at the highest taxonomic level, without a further increase at the most specific level, paralleling the pattern of superordinate-, basic-, and subordinate-level object concepts. From these action lists, brief stories were composed for each event. In Experiment 2, subjects made pairwise similarity judgments on the stories. The mean similarity of events increased with specificity, as expected. But differentiation of categories (within-category similarity compared to between-category similarity) was highest for super-ordinates, contrary to results with object categories. In Experiment 3, subjects were fastest in recognizing actions as belonging to events named at the basic level. In Experiment 4, subjects predominantly chose basic-level terms to name stories. We conclude that event taxonomies do show basic-level structure, albeit a less sharply defined and less stable structure than in object taxonomies. The benefits and hazards of extending models of object concepts to other entities, such as social events, are discussed.     

Acquiring English at different ages: The English displacement effect and other findings

An analysis of the language backgrounds of 237 persons in a psychology department subject pool is presented. Specific findings indicate that (a) only about two-thirds of the subjects were native speakers of English, (b) native English speakers can be divided into several different groups on the basis of bilingual background and age of acquisition of their second language, (c) the number of native English speakers who would be considered ideal for psycholinguistic experiments in English (e.g., monolinguals and bilinguals who acquired a second language in or after adolescence) is only about a third of the sample, (d) nonnative English speakers appear to have their native, non-English-language abilities reduced as a function of their acquisition of English; that is, English appears to displace other languages that a person knows (the English displacement effect), and (e) age of English acquisition is shown to be an important factor, by correlating negatively with rated English abilities and reported Scholastic Aptitude Test (SAT) scores, and positively with rated ability in a non-English language.Portions of this research were first presented at the 59th annual meeting of the Eastern Psychological Association in Buffalo, New York, April 1988. I gratefully thank Doris Aaronson for the numerous comments she made on earlier versions of this paper.