Based upon prior research showing thac the error associated with the Sander parallelogram is maximal when the diagonal lines are physically omitted rather than physically present, an attempt was made to determine if a similar finding might result from eliminating the shaft in the Mueller-Lyer illusion. An interaction was found between shaft vs no-shaft condition and fins-in vs fins-out. Eliminating the shaft significantly increased error in the fins-in condition and significantly decreased error in the fins-out condition. The results were judged consonant with the previous study involving the Sander parallelogram.In a previous study by the authors (Runyon & Cooper, 1970), we examined the effects of systematically redilcing the n~unber of component lines in the Sander parallelogram upon judgments of the relative lengths of the diagonal lines. W e found the illusion maximal when the parallelogram was reduced to its minimal form, viz., three parallel lines remained, with all other lines including the diagonals omitted.Gregory (1966) reported a similar comparison with the Mueller-Lyer illusion in which the shaft portion between the fins was included or omitted. Although he did not report data, he indicated that elimination of the shaft produced a more "labile" response, which we interpreted to mean "less stable." Since our prior results ( 1970) lead to highly stable and reproducible errors, we decided to investigate systematically the effect of the removal of the shaft upon the magnitude of the Mueller-Lyer illusion.Based upon a straightforward generalization of the results with the Sander parallelogram to the MueUer-Lyer illusion, we hypothesized that the no-shaft conditions would produce maximal error scores.
METHOD
SubjectsUndergraduate students (27 male, 21 female)' selected on a voluntary basis from introductory psychology courses served as Ss.
Potential theory encompasses a new set of observations growing out of a study of difficulties encountered in using Licklider's rat shocker. The theory explains these difficulties, gives meaning to the observations, and provides new techniques for solving many of the problems encountered in shocking animals. In the course of the study a promising new shock stimulus using dielectric electrodes was discovered. Finally a specific practical solution to the problem of shocking monkeys is presented, an electric field shocker.
Fresh leaves and bracts of poinsettia (Euphorbia pulcherrima) were fed to 46 Sprague-Dawley rats. The animals were observed for 1 week for changes in weight or behavior. The animals were then sacrificed in ether and examined for changes in thyroid and adrenal weights. One group was also examined for damage to the duodenum, jejunum, and ileum. No lesions or other signs of intestinal damage were observed. None of the groups showed any change in behavior or any significant change in body weight or adrenal weight. Only one group showed a significant increase in thyroid weight.
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