触觉空间精确性与触觉神经元密度相关联的验证

本研究应用栅栏定向任务,通过对小学一年级儿童和大学生的触觉敏感性的比较,验证触觉敏感性与神经元密度的关系。结果表明：对较大的易于分辨的刺激,成人可以完成得较好,而对较细小的难于分辨的刺激,儿童成绩更好。本研究验证了高感受单元密度对应较强的触觉敏感性的假设。     

Ecological influences in youth crisis shelters: Effects of social density and length of stay on youth problem behaviors

For 472 consecutive days we monitored the number of youths residing in a crisis shelter for adolescents, the average length of stay for the youths residing in the shelter on each day, and the number of problem behaviors occurring within the shelter on a daily basis. We analyzed these data using a combination of time series and logistic regression techniques to fit a model that would predict the occurrence of a problem behavior on any given day. After controlling for significant time trends in the data, our results indicate that both the number of youths in the shelter and the proportion of youths who have resided in the shelter longer than 14 days are significantly associated with a problem behavior occurring on any given day. The number of youths in the shelter and the probability of a problem behavior occurring correlated significantly. However, as the proportion of youths who resided in the shelter longer than 14 days increased, the probability of a problem behavior occurring decreased.     

Structure in semantic memory: A probabilistic approach using a continuous response task

In the continuous response (CR) task, the subject is given the name of a familiar category and must respond with category examples within a fixed time limit. The response sequence and the interresponse times are the measured variables. A general model is proposed for performance in the CR task. The time taken to generate a response is identified with the shortest search time from among a set of simultaneous search processes. Each response has a generation probability that is a function of the parameters governing the search process durations. Data involving the category states in the United States are used to test the model. The model accounts for the performance of nearly all individuals in these data.This article is based on a dissertation completed at the University of California-Berkeley in partial fullfillment of the requirements for the Ph.D. degree in psychology. Portions of the article were presented at the joint meeting of the Psychometric and Classification Societies (June 1984) and at the meeting of the Society for Mathematical Psychology (August 1984). The authors wish to thank Barbara Mellers, Juliet Schaffer, Steve Palmer, and Eleanor Rosch for helpful comments.     

On the distinction between open and closed economies.

Open and closed economies have been assumed to produce opposite relations between responding and the programmed density of reward (the amount of reward divided by its cost). Experimental procedures that are treated as open economies typically dissociate responding and total reward by providing supplemental income outside the experimental session; procedures construed as closed economies do not. In an open economy responding is assumed to be directly related to reward density, whereas in a closed economy responding is assumed to be inversely related to reward density. In contrast to this predicted correlation between response-reward relations and type of economy, behavior regulation theory predicts both direct and inverse relations in both open and closed economies. Specifically, responding should be a bitonic function of reward density regardless of the type of economy and is dependent only on the ratio of the schedule terms rather than on their absolute size. These predictions were tested by four experiments in which pigeons' key pecking produced food on fixed-ratio and variable-interval schedules over a range of reward magnitudes and under several open- and closed-economy procedures. The results better supported the behavior regulation view by showing a general bitonic function between key pecking and food density in all conditions. In most cases, the absolute size of the schedule requirement and the magnitude of reward had no effect; equal ratios of these terms produced approximately equal responding.     

基于语料库统计的“音-形”激活概率及加工机制

为了了解心理词典中语音与汉字的联结情况以及从音到形的加工机制,研究首先计算出了基于语料库统计的“音-形”激活概率(某个音节激活其对应汉字的概率),并通过一个听写实验来验证这种激活概率是否反映实际加工中的激活情况。结果证明基于语料统计得到的“音-形”激活概率基本可以预测实际的“音-形”激活情况,表现为:“音-形”激活概率越高的汉字被激活的概率和强度越高,并且有明显的优势字效应; 该统计概率具有可独立于其他影响因素的预测功能。     

The precise time course of lexical activation: MEG measurements of the effects of frequency, probability, and density in lexical decision

Visually presented letter strings consistently yield three MEG response components: the M170, associated with letter-string processing (Tarkiainen, Helenius, Hansen, Cornelissen, & Salmelin, 1999); the M250, affected by phonotactic probability, (Pylkk?nen, Stringfellow, & Marantz, 2002); and the M350, responsive to lexical frequency (Embick, Hackl, Schaeffer, Kelepir, & Marantz, 2001). Pylkk?nen et al. found evidence that the M350 reflects lexical activation prior to competition among phonologically similar words. We investigate the effects of lexical and sublexical frequency and neighborhood density on the M250 and M350 through orthogonal manipulation of phonotactic probability, density, and frequency. The results confirm that probability but not density affects the latency of the M250 and M350; however, an interaction between probability and density on M350 latencies suggests an earlier influence of neighborhoods than previously reported.     

EFFECTS OF CALORIC LEVEL ON RUMINATING

A series of recent studies has shown that a number of dietary variables affect ruminative behavior in institutionalized retarded persons. This experiment extends an earlier study that examined the influence of the caloric level of the diet on the frequency of ruminating. Subjects consumed regular portions of food that varied between phases from normal to high caloric levels. The data show a clear but modest inverse relation between the caloric value of the diet and the rates of postmeal ruminating.     

Impact of artificial fissioning and social networks on levels of aggression and affiliation in primates

Levels of aggression may be affected by stability of social relationships or by population density. A number of studies of nonhuman primates have indicated that spatial density influences agonistic activity levels less than does social density. Artificial fissioning of a captive troop of rhesus macaques was undertaken and the resultant differences in patterns of aggression and affiliation were examined. If population density has a major effect on levels of aggression, then fissioning will result in a decrease in aggression; if social stability has a major effect on levels of aggression, then fissioning is likely to be accompanied by an increase in aggression. An increase in rates of both aggressive and affiliative behavior resulted from artificial troop fissioning. These findings concur with other studies that have concluded that social stability is a more important determinant of primate aggression than is population density. Nonhuman primates use affiliative mechanisms to adjust their behavior when population density increases such that potentially adverse consequences of crowding are avoided.     

Initial excitatory conditioning with the truly random control procedure in rats: The effects of density of the conditioned stimulus

The present experiments were designed to test whether initial excitatory conditioning to a stimulus was obtained, using a within-subject design of the truly random control (TRC) procedure, and to examine the effects of the density of the conditioned stimulus on it. In Experiment 1, the effect of the three levels of CS density (50%, 25%, 20%) was assessed at six different stages of training, using the conditioned suppression of licking in rats. Although all of the groups given the TRC procedure showed evidence of initial excitatory conditioning, it was more marked in the group with the highest CS density than in the other groups. Experiment 2 confirmed the results of Experiment 1, using a between-subject design. The findings are in line with predictions from the Rescorla-Wagner model, and are discussed with reference to other contemporary theories of associative learning.