Does the "eyes lead the hand" principle apply to reach-to-grasp movements evoked by unexpected balance perturbations?

A fundamental principle that has emerged from studies of natural gaze behavior is that goal-directed arm movements are typically guided by a saccade to the target. In this study, we evaluated a hypothesis that this principle does not apply to rapid reach-to-grasp movements evoked by sudden unexpected balance perturbations. These perturbations involved forward translation of a large (2 × 6 m) motion platform configured to simulate a “real-life” environment. Subjects performed a common “daily-life” visuo-cognitive task (find a telephone and make a call) that required walking to the end of the platform, which was triggered to move as they approached a handrail mounted alongside the travel path. A deception was used to ensure that the perturbation was truly unexpected. Eleven of 18 healthy young-adult subjects (age 22-30) reached to grasp or touch the rail in response to the balance perturbation. In support of the hypothesis, none of these arm reactions was guided by concurrent visual fixation of the handrail. Seven of the 11 looked at the rail upon first entering the environment, and hence may have used “stored” central-field information about the handrail location to guide the subsequent arm reaction. However, the other four subjects never looked directly at the rail, indicating a complete reliance on peripheral vision. These findings add to previous evidence of distinctions in the CNS control of volitional and perturbation-evoked arm movements. Future studies will determine whether similar visuo-motor behavior occurs when the available handhold is smaller or when subjects are not engaged in a concurrent visuo-cognitive task.     

Neural enhancement and attenuation induced by repetitive recall

Learning is the process of accumulating information. Repetition can make the process of retrieving information more efficient. The mechanisms by which repetition facilitates the retrieval process, however, are not yet clear. Here, we used event-related functional magnetic resonance imaging to investigate the effects of repetition on cued recall. In this study, participants were asked to encode visually presented semantically unrelated word pairs. The word presented on the left side served as the cue, and the word presented on the right side was the target. In the first test phase, participants were presented with the cue and asked to recall the associated word (target) from the study phase. The second test phase was performed 20 min later using the same method. Participants responded orally during the interval between image acquisitions, and no feedback was provided. Neural activity for identical stimuli and responses across the two tests were compared. As compared with the first test phase, the right dorsolateral prefrontal, bilateral inferior parietal, and precuneus regions showed greater activity and the left inferior frontal areas showed reduced activity during the second test phase. These shifts in neural activity that occurred with repetition may reflect the dynamics of the retrieval process.     

A comparison of response cost and differential reinforcement of other behavior to reduce disruptive behavior in a preschool classroom

This study investigated the effectiveness of response cost and differential reinforcement of other behavior (DRO) in reducing the disruptive behaviors of 25 children in a preschool classroom. Using an alternating treatments design, disruptive behavior was reduced when the participants earned tokens for the absence of disruptive behavior (DRO) or lost tokens for the occurrence of disruptive behavior (response cost). Initially, DRO was more successful in reducing the number of disruptive behaviors; however, over time, response cost proved to be more effective.     

Multimedia comprehension skill predicts differential outcomes of web-based and lecture courses

College students (134 women and 55 men) participated in introductory psychology courses that were offered largely online (on the World Wide Web) or in a lecture format. Student comprehension skills were inferred from their scores on a multimedia comprehension battery. The learning of content knowledge was affected interactively by comprehension skill level and course format. Differences between format increased with comprehension skill such that the Web-based course advantage became greater as comprehension skill increased. This same pattern was not seen when self-reports of comprehension ability were used as the predictor. Furthermore, comprehension skill did not predict course satisfaction. Generally, students of all skill levels preferred the lecture courses.     

Release from proactive interference by experimental amnesia: electroconvulsive shock improves radial-arm maze performance in rats

Rats were trained in an eight-arm radial maze and tested using a proactive interference (PI) procedure. Each test trial consisted of forced choices of four randomly selected arms followed, after a 2-h delay, by free choices among all eight arms. Normally, rats chose correctly during the free choices by entering and retrieving food from the four arms not yet visited during the test trial. Occasionally, an interference trial preceded the test trial by 1.5 or 3 h; interference trials consisted of forced choices of another four arms and an immediate test. The presence of an interference trial lowered test-trial performance (PI). Electroconvulsive shock (ECS) administered immediately after the interference trial had no effect; i.e., PI was still observed. When ECS was administered at the midpoint of the 3-h intertrial interval, performance increased to control (no ECS, no PI) levels. Such release from PI, however, was not obtained, and test-trial performance remained inaccurate when ECS was delivered immediately after the forced choices of the test trial (either 1.5 or 3 h after the interference trial).     

The relationship between comprehension and metacomprehension ability

We investigated the relationship between the ability to comprehend text and the ability to predict future performance and to assess past performance on text. Subjects were poor at predicting performance, which may be why prediction accuracy did not relate to measures of comprehension ability. Measures of comprehension ability did relate to the accuracy with which subjects assessed their performance on tests. Better and faster comprehenders judged their relative levels of test performance over sections of text more accurately than did poorer and slower comprehenders.     

Age differences in implicit memory: fragmented object identification and category exemplar generation.

In a cross-sectional study of 164 participants aged 21 to 91, the authors examined age differences on two implicit tests, fragmented object identification (FOI) and category exemplar generation (CEG), and on tests of explicit memory, attention, and verbal fluency. FOI results revealed impaired perceptual skill learning in those over 60 and a decrease in perceptual priming across young, middle-aged, and older groups. CEG priming was impaired in those over 80. Regression analysis revealed explicit contamination of priming on both the FOI and CEG tests. Across the three implicit measures, age accounted for 4 to 13% of the variance when explicit memory was controlled. Semantic fluency predicted CEG priming, suggesting possible frontal lobe involvement on the test. Altogether, results indicate that age has a small but reliable influence on implicit memory.     

Measuring study time distributions: Implications for designing computer-based courses

In both traditional lecture-test courses and courses delivered over the World-Wide Web (WWW), both beginning and experienced college students reported studying almost exclusively just before exams. Automatic measures (computer records, WWW page hits, and electronic mail archives) confirmed the self-reported distributions of study times. Weekly deadlines produced weekly volleys of taking on-line quizzes, a pattern that was reflected in self-reports of study times. However, on-line study materials were used primarily for review for regularly scheduled in-class exams. Thus, regardless of course format, students engaged in massed practice and did not experience study aids at appropriate times. Computer technology provides new forms of learning for students, as well as opportunities for instructors to observe patterns of student study time. Management of instructional contingencies will be necessary to bring students into contact with the rich cognitive aids enabled by technology.     

Efficiency of arithmetic operations in bilinguals as a function of language

English-Spanish bilinguals solved simple arithmetic problems and were required to respond In their preferred (P) language. the language In which they originally learned arithmetic, or In their nonpreferred (NP) language. Each arithmetic problem required one. two, or three addition operations. Reaction time was a linear function of number of operations. The intercept for the P language was lower than that for the NP language. but there were no differences In slope. The intercept difference was interpreted In terms of translation time. either as translation of the sum from the P to the NP language or as translation from an abstract representation to the NP as opposed to the P language.     

Assessment of field dependence in young children

In a series of exploratory studies to develop instruments for measuring field dependence in young children, a total of 312 Japanese middle-class children, ages 5 to 6, served as subjects. Without changing the essential nature of the original test, the geometric embedded-figures test attained relatively high internal consistency (KR-20 in the .80's) and stability (R = .83 to .52, at intervals of 1.5 to 13 mo.). Correlation pattern between the Embedded Figures Test and Wechsler subscales similar to that of older subjects was influenced by the speed factor in embedded figures and Wechsler performance scales. Correlation between Kato's portable Rod-and-frame test and embedded figures was significant only in boys. In addition, the correlation pattern between the rod and frame and the preschool Wechsler was not consistent with Witkin's conceptualization. A newly developed darkroom Rod-and-Frame Test correlated with embedded figures for both sexes. Additional analyses indicated the need for more refined instructions to subjects regarding the concept of upright. Some children had more than one anchoring point for responding. Nyborg's scoring method and the relationship of Piagetian spatial concept to rod-and-frame performance are discussed.