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.     

Interaction of genetics and separation in canine hyperkinesis and in differential responses to amphetamine

A model of childhood hyperkinesis, using the Telomian-beagle hybrid dog, is described, demonstrating the interactions of genetics and separation in the development of this syndrome and in the favorable responses of some of these dogs to amphetamine. This work represents the collaboration of three laboratories, utilizing chiefly methods of inhibitory training. Inducing separation distress enhanced the resistance to inhibitory training and the favorable responses to amphetamine.     

Distributed study facilitates infants’ delayed recognition memory

Infants of 5–6 months of age were tested for recognition of briefly presented photographs of faces. The interaction typically obtained with adults, a beneficial effect on retention due to the temporal spacing of study, was obtained with these infants. The results suggest that the distribution effect reflects a fundamental and automatic process of human memory.     

Measurement of sexual arousal in several paraphilias: The effects of stimulus modality,instructional set and stimulus content on the objective

The effects of instructional set (become aroused or suppress arousal), stimulus modality (videotape, audiotape, slides, free fantasy) and stimulus content (paraphilic or non-paraphilic) on sexual arousal, as measured by penile plethysmograph, of six different groups of paraphilics, pedophiles, rapists, exhibitionists, homosexuals, sado-masochists and fetishists, were determined. The results showed significant main effects of instructional set and of stimulus modality (videotape was clearly more arousing) as well as several complex interactions of diagnostic group with the other independent variables.