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.     

Isolating the typicality effect in semantic memory

An experiment was conducted to isolate the typicality effect in the overall categorization process. Subjects were required to indicate whether or not a probe word was a member of one of a variable number of categories held in memory. The typicality of the probe word, with respect to its superordinate category, was varied as was the physical quality of the probe. These manipulations were designed to test predictions drawn from Collins and Loftus (1975) and Anderson and Reder (1974), as well as a prediction based on the well-known effect of semantic context on word perception. A fourth prediction was drawn from a proposed model which postulates successive access of categories and locates the typicality effect in a within-category search stage. Typicality proved to be additive with stimulus quality and set size, but interacted with response type. These results were interpreted as support for the successive-access within-category search model while disconfirming the alternative predictions.     

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.