Accommodation to increased accuracy demands by the right and left hands

This study was designed to identify the phase of rapid aimed movements responsible for hand differences in motor skill, and to evaluate potential differences between the hands in accommodating to greater accuracy demands. In both experiments, an accelerometer mounted on a stylus allowed key changes in acceleration to be used to partition the movement into phases. In Experiment 1, slower left hand movement times were attributable primarily to a terminal homing-in phase, especially as target size decreased. Since error rates varied as a function of hand and target size, speed-accuracy trade-offs may have occurred. Experiment 2 rigidly controlled error rate and confirmed the major hand difference to occur in the latter phase of the movement where error correction is presumed. Although less pronounced, adjustments were made in the earlier movement phases as well. Accommodation to greater accuracy demands involved moving the stylus closer to the target before decelerating to engage in error correction. This adjustment to gain enhanced precision was more pronounced in the left hand.     

Reaction time methods in the study of motor programming: the precuing of hand, digit, and duration

Recent reaction time analysis of motor programming has utilized a precue stimulus that provides advance information about some or all of the attributes for the upcoming motor response. This kind of precue typically confounds the number of remaining stimuli with the motoric processes under investigation (Zelaznik, 1978). In Experiments 1 and 2 the precuing of hand, digit, and duration of a key press response was manipulated. A new precuing procedure was utilized that does not confound the number of stimuli with the motoric processes under investigation. The findings of Experiments 1 and 2 demonstrate that none of the advance information was helpful in reducing reaction time and as such, suggest that these features of movement are not selected in any particular order. Experiment 3 compared this new method of precuing to the other, traditional method. The results of this experiment suggested that there is parallel processing of the perceptual and motor mental operations in this reaction-time task, since there was an underadditive interaction between the number of stimulus response alternatives and the non-precued movement dimensions. This paper highlights problems inherent in the utilization of precursing methods to understand motor programming processes. It appears that a better understanding about the variables involved in movement control is necessary before examining the order of selection of those variables.     

Symmetry and transitivity of conditional relations in monkeys (Cebus apella) and pigeons (Columba livia)

In Experiment 1 six monkeys were tested with discriminative relations that were backward relative to their training in a 0-second conditional (“symbolic”) matching procedure. Although there was some indication of backward associations, the evidence was generally weak, and statistical evaluations did not reach conventional significance levels. Unlike children, who show backward associations to the point of symmetry, monkeys and pigeons display at best only weak and transient backward associations. In Experiment 2 associative transitivity was assessed across two sets of conditional matching tasks. All four monkeys tested demonstrated strong transitivity. In contrast, in Experiment 3 there was no evidence of transitivity in three pigeons tested under conditions closely comparable to those of Experiment 2. These results may identify some key features of interspecies differences and contribute to analyses of serial learning in animals.     

Saying and doing: A contingency-space analysis

Correspondences between verbal responding (saying) and nonverbal responding (doing) may be organized in terms of the classes of verbal/nonverbal relations into which particular instances of verbal/nonverbal response sequences can enter. Contingency spaces, which display relations among events in terms of the probability of one event given or not given another, have been useful in analyses of nonverbal behavior. We derive a taxonomy of verbal/nonverbal behavior relations from a contingency space that takes into account two conditional probabilities: the probability of a nonverbal response given a verbal response and that probability given the absence of the verbal response. For example, positive correspondence may be said to exist as a response class when the probability of doing is high given saying but is otherwise low. Criteria for other generalized classes, including negative correspondence, follow from this analysis.     

Quantitative assessment of infant reaching movements

We have identified a fundamental property of human motor behavior as a tight coupling of the curvature-speed relationship in the reaching movements of 5- to 9-month-old infants. This relationship termed a movement unit, occurs regardless of the distance of duration of the reach and in spite of the developmental change that occurs in grasping during this period. Movement unit durations are tightly clustered around 200 ms regardless of overall duration or distance or the position of the unit in the reach. The curvature-speed coupling has been identified by others in adult reaching and handwriting. Models of biological motor control must account for this invariant relationship.     

Ethical dilemmas in forensic evaluations

Ethical issues emerging from forensic assessments are addressed from clinical and research perspectives. The relevance of agency, forensic identification, and attitudes toward defendants are explored within the framework of ethical practice. Finally, the ethical role of mental health professionals in the courtroom, the scope and basis of their testimony, and the rendering of conclusory opinions are discussed within a psycholegal context.     

Conflict of interest between therapist-patient confidentiality and the duty to report sexual abuse of children

All 51 jurisdictions in the United States require physicians to report suspected child abuse. In most jurisdictions, reporting requirements override both confidentiality and privilege associated with the physician-patient relationship. The authors review the literature relevant to the conflict between privacy and reporting abuse and report the results of a national survey of therapists at sex offender treatment units. They discuss ethical problems experienced under these statutes by therapists who attempt to provide treatment for sex offenders, and by therapists who are required to report past instances of child abuse even when there is no evidence of ongoing abuse.     

Function-altering effects of contingency-specifying stimuli

Contingengy-specifying stimuli (CSSs) can function differently than discriminative stimuli. Rather than evoking behavior due to a history of discrimination training, they alter the function of other stimuli and, therefore, the behavioral relations involving those stimuli. CSSs can alter the evocative function of discriminative stimuli, establishing operations, and conditional stimuli, as well as the efficacy of reinforcing and punishing stimuli and of stimuli that can function in second-order respondent conditioning. The concept of function-altering CSSs has implications for such areas of interest as stimulus equivalence, the terminology involving "rules" and "rule-governed behavior," and the way in which behavior analysts view the effects of such basic processes as reinforcement and punishment.     

Conditional relations by monkeys: Reflexivity, symmetry, and transitivity

Two cynomolgous macaques categorized six colors into two groups of three after conditional discrimination training (zero-delay symbolic match-to-sample). The procedures resulted in the establishment of relations among the elements of each set-relations that were not specifically trained and that can be characterized by the properties of reflexivity, symmetry, and transitivity. Each set of colors was related to a characteristic pattern of responding: One response pattern involved temporal duration (press and hold the response keys); the second response pattern entailed repeated pressing and releasing of the response keys (fixed ratio 8). Six combinations of two colors were trained, three combinations from each set. After discriminative performance stabilized for each monkey, they were tested with 10 additional color combinations, all of which differed from the training combinations. The conditional relations established between test combinations can be characterized as stimulus equivalence. The training procedures were analogous to the procedure of using category names, and have implications for understanding the function of language in the formation of equivalence classes.     

目的、意向和意识

本文提出了一个意向性目标搜寻的计算机模型,它有两个部分,静态部分包括一个目标表征和到达这个目标的程序。动态部分是一个感觉输入、中间信息加工,行为输出的重复的反馈循环。人类意向必然伴有意识,但机器人则可能无意识而有意向。 利用目标搜寻系统机器人模型,我们对目标搜寻系统的目的连续统下了定义;这个连续统从简单的直接反应系统一直到意向性系统。对这个目的连续统有两种传统的解释:一是柏拉图、亚里士多德和普罗提诺的终极原因理论,二是希腊原子论者和现代进化生物学家的还原主义学说。本文评价了这些学说。 本文考察了几种类型的意识机能,提出了以自动机为依据的意识理论,比较了人类和计算机。从计算机结构的角度来看,人类意识是一类特殊的计算机控制系统。