Specification of direction and duration during programming of discrete sliding movements

Summary Two experiments on duration programming of a discrete sliding movement in choice reactions are reported. In the first experiment it was examined whether duration of movement might be preprogrammed when varied across sessions. The result suggested that programming of movement duration is dependent on direction uncertainty. Experiment 2 used the movement precue technique in an attempt to further examine programming of movement duration and direction. Movement duration, movement direction, movement form and foreperiod duration were manipulated. When duration was not precued, a duration effect was found, while precueing resulted in disappearance of the duration effect, demonstrating that duration of sliding movements can be preprogrammed. Moreover, (pre)programming duration was independent of direction uncertainty, supporting an independent order notion of programming of these response variables. Evidence that motor preparation comprises different processing stages was derived from the additive effects of foreperiod duration and of the movement variables duration and direction.     

Nonsexist curricula,sex of teacher,and children's sex-role learning

This study examined the impact of nonsexist curricula and teacher's sex on children's sex role learning. Thirty-two boys and 32 girls, aged three to five, were equally divided among four programs: nonsexist curriculum, female director; nonsexist curriculum, male director; control curriculum, female director; and control curriculum, male director. Sex role discrimination and preference were measured at the beginning and end of a six-month period. Exposure to the nonsexist curriculum produced significantly greater reductions in sex stereotyping on all measures than exposure to the control curriculum. Moreover, children in the male-directed nonsexist program displayed greater decreases in stereotypic knowledge and preference for sex-typed children's activities than those in the female-directed nonsexist program, while children in the male-directed control program showed more stereotypic increases on these measures than their counterparts in the female-directed control program. Finally, children under the direction of an opposite-sex teacher exhibited less stereotypic changes in preference for adult activities than children under the direction of a same-sex teacher. Implications for early childhood programs are discussed.This research was partially supported by an Oregon State University Foundation grant from the Shell Foundation and a grant from the Milne Computer Center.     

Representation of linear orders

Two binary classification tasks were used to explore the associative structure of linear orders. In Experiment 1, college students classified English letters as targets or nontargets, the targets being consecutive letters of the alphabet. The time to reject nontargets was a decreasing function of the distance from the target set, suggesting response interference mediated by automatic associations from the target to the nontarget letters. The way in which this interference effect depended on the placement of the boundaries between the target and nontarget sets revealed the relative strengths of individual interletter associations. In Experiment 2, students were assigned novel linear orders composed of letterlike symbols and asked to classify pairs of symbols as being adjacent or nonadjacent in the assigned sequence. Reaction time was found to be a joint function of the distance between any pair of symbols and the relative positions of those symbols within the sequence. The effects of both distance and position decreased systematically over 6 days of practice with a particular order, beginning at a level typical of unfamiliar orders and converging on a level characteristic of familiar orders such as letters and digits. These results provide an empirical unification of two previously disparate sets of findings in the literature on linear orders, those concerning familiar and unfamiliar orders, and the systematic transition between the two patterns of results suggests the gradual integration of a new associative structure.     

The micro-structure of tapping movements in children

In order to investigate the development of movement speed in relation to movement organization, children of 5, 6, 7, 8 and 9 years of age and adults carried out a reciprocal tapping task, in which time pressure and distance were manipulated. The duration, velocity, acceleration and accuracy of the movements were compared between age groups. Age differences appeared mainly in the homing time, not in the duration of the distance covering movement phase. Accuracy and velocity of the distance covering movement phase differed with age. Time pressure affected the homing time, but not the duration of the distance covering phase. Distance manipulation affected mainly the velocity and duration of the distance covering movement phase and the homing time. In the discussion it is contended that age differences in homing time may be related to both the accuracy of the distance covering movement phase and the rate of information processing of the subject.     

Rapid error correction during human arm movements: evidence for central monitoring

Studies were made of rapid error correction movements in eight subjects performing a visually guided tracking task involving flexion-extension movements about the elbow. Subjects were required to minimize reaction times in this two-choice task. Errors in initial movement direction occurred in about 3% of the trials. Error correction times (time from initiation to reversal of movement in incorrect direction) ranged from 30-150 ms. The first sing of correction of the error movement was a suppression of the electromyographic (EMG) activity in the muscle producing the error movement. This suppression started as early as 20-40 ms after the initiation of the error-related EMG activity and as much as 50 ms before any overt sign of limb movement. The correction of the error movement was also accompanied by an increase in the drive to the muscle which moved the arm in the correct direction. This increased activity always occurred after the initiation of the error movement. it is concluded that the first step in the error correction, suppression of drive to the muscle producing the error movement, cannot be based on information from the moving limb. It is thus suggested that this earliest response to the error movement is based on central monitoring of the commands for movement.     

A maximum likelihood hierarchical disaggregate model for predicting choices of individuals

The absence of operational disaggregate lexicographic decision models and Tversky's observation that choice behavior is often inconsistent, hierarchical, and context dependent motivate the development of a maximum likelihood hierarchical (MLH) choice model. This new disaggregate choice model requires few assumptions and accommodates the three aspects of choice behavior noted by A. Tversky (1972, Journal of Mathematical Psychology, 9, 341–367). The model has its foundation in a prototype model developed by the authors. Unlike the deterministic prototype, however, MLH is a probabilistic model which generates maximum likelihood estimators of the aggregate “cutoff values.” The model is formulated as a concave programming problem whose solutions are therefore globally optimal. Finally, the model is applied to data from three separate studies where it is demonstrated to have superior performance over the prototype model in its predictive performance.     

Children's understanding of conversational principles

Sixteen preschool, first-, and third-grade children were presented with short stories ending with a verbal statement by a story character. Two alternative ending statements were provided. One alternative violated a postulate (H. P. Grice, 1975, in P. Cole & J. Morgan (Eds.), Syntax and Semantics (Vol. 3), New York: Academic Press) or a reasonable request condition (D. Gordon & G. Lakoff, 1971, Conversational postulates, papers from the seventh regional meeting of the Chicago Linguistic Society, University of Chicago, Department of Linguistics), while the other alternative did not. The child's task was to choose the “funny or silly“ ending, i.e., the violation. Data analysis showed that 100% of the third-graders, 83% of the first-graders, and 19% of the preschoolers performed with significant (P < .02) accuracy. These results suggest that children's understanding of conversational principles improves considerably between preschool and first grade. There were no significant differences among four types of conversational principles examined.     

Intergroup contact: The typical member and the exception to the rule

Three studies examined the role of the perceived typicalness of an out-group member on her effectiveness in improving evaluations of her group. Subjects were students at two adjacent colleges. In the first study they interacted with a member of the out-group college. The interaction was either pleasant or unpleasant, and the contact person either confirmed or disconfirmed several stereotypes of the out-group (typicalness manipulation). Subjects evaluated the out-group most favorably when they interacted with the typical-pleasant member of the out-group. The second study demonstrated that contact with a highly typical member is not beneficial if her typicalness is based on stereotypes that reflect negatively on the subject's in-group. Several explanations of the typicalness findings were considered in a third study. Support was found for the hypothesis that the more typical member is perceived to be more predictive of the personality and actions of other out-group members.     

Context effects on the perceived physical attractiveness of faces

Four experiments were conducted to study the nature of context effects on the perceived physical attractiveness of faces. In Experiment 1, photos of faces scaled on attractiveness were presented in sets of three, with target faces appearing in the middle flanked by two context faces. The target faces were of average attractiveness, with the context faces being either high, average, or low in attractiveness. The effect of the context was one of assimilation, rather than contrast, regardless of whether the persons in the photos were portrayed to be associated. This result was interpreted in terms of a “generalized halo effect” for judgments of the physical attractiveness of stimuli within a group. Presenting the persons of a set as friends enhanced the perceived attractiveness of the target face but only when the context did not contain a face of low attractiveness. In Experiment 2, the assimilation effect was observed to carry over to influence ratings of the target faces several minutes after the context faces had been removed. Experiment 3 showed the assimilation effect to be robust regardless of whether the context was composed of two faces or one, but Experiment 4 showed the assimilation effect to be evident only when the context faces were presented simultaneously with the target.