Relative costs and statistical power in the extreme groups approach

The relationship between variables in applied and experimental research is often investigated by the use of extreme (i.e., upper and lower) groups. Recent analytical work has provided an extreme groups procedure that is more powerful than the standard correlational approach for all values of the correlation and extreme group size. The present article provides procedures to optimize power by determining the relative number of subjects to use in each of two stages of data collection given a fixed testing budget.The opinions or assertions contained herein are those of the writers and are not to be construed as official or reflecting the views of the Navy Department.Edward F. Alf, Jr. is also affiliated with the Department of Psychology, San Diego State University.     

Do the mentally retarded have poor memory?

The hypothesis that mentally retarded persons have a short-term memory deficit whixh is due to inadequate rehearsal strategies is reexamined. A reevaluation of results of a number of experiments suggests that normal and retarded persons differ on short-term memory tasks, and the superiority of normals is present from the time of initial stimulus exposure. While some evidence for slope differences in retention curves is found in a few tasks, it is not strong support for memory differences. The hypothesis that “memory” differences are due to differential encoding as a result of more adequate rehearsal by the normal subjects is unacceptable. If this were the case, some differences in slope of retention curves could be expected unless rehearsal beyond the encoding stage was totally precluded. The review points to a need for an empirical reevaluation of the issue with a full recognition that deficits in particular processes may characterize some retarded persons and not others.     

The effect of alcohol on male aggression toward female targets

This study attempted to determine the effects of alcohol, verbal provocation, and target strategy on male aggression toward female targets. Intoxicated and nonintoxicated male research participants competed with a female confederate in a reaction time task designed to measure aggression. Intoxicated participants responded more aggressively than did nonintoxicated participants. Verbal provocation had no effect on participants' aggressive response. Effects of target strategy and trial outcome lent support to a cognitive disorganization interpretation of the effect of alcohol on aggression.     

Aversive procedures: The minnesota experience

Aversive and deprivation procedures for controlling and reducing challenging behaviors have received increasing attention. Many states have adopted guidelines on the use of these procedures treating persons with developmental disabilities. The Minnesota state rule promulgated in October, 1987 requires reviews from both local and state-wide review committees on permitted, but controlled procedures. Data generated from state-wide committees revealed that (a) state operated regional treatment centers (RTCs) employed individual habilitative training programs with controlled procedures more frequently than community-based agencies (b) a higher proportion of RTC submissions were for treatment of self-injury than submissions from community services, and (c) RTCs had a higher usage of mechanical restraints than community facilities with both services settings using manual restraints more frequently than all other controlled procedures combined. Reasons for the above differences in the two service settings were discussed.     

The perception of semantic relations in pictures

Three picture processing experiments are reported that present evidence of an “agent advantage effect,” that is, faster processing of the performer of the action depicted the agent of the action than of the element acted upon (the patient). Experiment 1 demonstrated the effect in a paradigm in which reaction time to manually indicate the location of a target (agent or patient) was faster for agent targets. Experiment 2 demonstrated that the critical time required for subjects to encode the agent was shorter than the time required for encoding patients. Experiment 3 again demonstrated the agent advantage effect in a directed attention paradigm. Together, the results of the experiments indicated that subjects were able to encode agent information faster than patient information. The results also indicated that subjects did not adopt a strategy whereby encoding of patient information was necessarily dependent upon encoding agent information.     

The generality of overselectivity in developmentally disabled children

A growing body of research suggests that low Mental Age (MA) autistic and retarded children show a unique stimulus control deficit, one that may cause many or most of their behavioral deficiencies. This problem, stimulus overselectivity, is evidenced when a child responds only to a restricted portion of the stimulus environment when compared with normal children. The purpose of this study was to assess whether this overselectivity is general across situations or whether it is restricted to certain stimulus/task conditions. Eight autistic children, who evidenced overselectivity on a preassessment task, and 8 normal children with similar MA levels participated. All children were trained on 3 tasks to determine if overselectivity varied as a function of different stimulus conditions. Each of the 3 tasks involved training a child to respond to (i.e., touch) a card containing a circle (S +) and to avoid a blank (S ?) card. In each case, the circle comprised a series of dots. The difference between the 3 circles (tasks) was the distance between the successive dots making up each circle. Also, in the minimal separation condition the dots were smaller in size and greater in number than in the larger separation conditions. Of concern was whether autistic children learned about the gestalt (i.e., the circle), which required attention to multiple cues, or whether children would overselect and respond to the dots. The results showed that (1) stimulus overselectivity was found not to be a generalized deficit in autistic subjects; instead, it varied as a function of the stimulus variables; and (2) the stimulus variables manipulated in this study similarly influenced the responding of both normal and autistic children. The implications of these data for a theory of overselectivity are discussed.     

Abstraction of contingency in concept learning

It is generally agreed that concept learning involves the abstraction of some general representation or schema. Just what is abstracted, however, and how it is used in the classification of sets of stimuli in the natural world or in the laboratory, remain outstanding questions. In this paper a hypothesis involving contingency abstraction is described as a possible solution to these questions. An experiment which manipulated measured contingency in a concept-learning task, and which offered empirical support for the hypothesis, is reported. The advantages of a contingency-abstraction theory of concept learning are briefly discussed.     

A biphasic 60-Hz synchronizer circuit for the recording of visually evoked responses in high-noise environments

A simple synchronizer clock circuit is described that aids in the rejection of 60-Hz noise from evoked potential measurements.