Perceived target displacement as a function of field movement and asymmetry

In two experiments induced movement of an object was produced to demonstrate that movement of the background influences the perceived localization of the object in space. The Roelofs (asymmetry) effect could be used to explain only part of the shift in localization in Experiment1. The asymmetry effect was excluded from Experiment2 by the procedure employed. It was concluded that the Roelofs effect is a sufficient, but not necessary, condition for the effects of induced movement to occur, and that relative displacement of the target and background plays an important part in the illusion. Furthermore, it was shown that the effects of induced movement can occur even when the border of the background remains stationary.     

The perception of size in a distorted room

This study was concerned with determining the factors important in the size illusion occurring with respect to extraneous objects introduced into an Ames’ monocular distorted room, It was asserted that the distortion in the room was unnecessary in order for the size illusion to be present, A rectangular room plus the extraneous objects produces the same stimulus conditions found in the Ames’ room and, hence, should produce the same illusion in perceived size, In an experiment using a rectangular room, 24 Os judged the size and distance of objects at the same or different distances behind the windows. As in the case of the Ames’ room it was found that the objects of physically equal size were perceived to be in the plane of the windows with the more distant objects appearing to have the smaller size. These results are explained in terms of the action of the equidistance tendency making the objects appear at the distance of the windows and the concept that objects in the same apparent fronto-parallel plane must have equal values of perceived size per unit of retinal size.     

On accuracy in reliability estimation

This study in parametric test theory deals with the statistics of reliability estimation when scores on two parts of a test follow a binormal distribution with equal (Case 1) or unequal (Case 2) expectations. In each case biased maximum-likelihood estimators of reliability are obtained and converted into unbiased estimators. Sampling distributions are derived. Second moments are obtained and utilized in calculating mean square errors of estimation as a measure of accuracy. A rank order of four estimators is established. There is a uniformly best estimator. Tables of absolute and relative accuracies are provided for various reliability parameters and sample sizes.     

Listener judgements of fluency: The effect of part-word CV repetitions and neutral vowel substitutions

Three groups of forty subjects listened individually to one of four recordings of voluntary disfluencies. Disfluencies took the form of either one or two-unit repetitions and contained either the correct vowel or the stressed neutral vowel in place of the correct vowel. Each listener rated the speaker on a five point scale where 1 represented the most fluent rating and 5 represented the least fluent rating. Results indicated no significant difference in the ratings of the four recordings. Overall severity ratings decreased as training in speech pathology increased. Graduate students in Speech Pathology rated three of the four tapes as being significantly more fluent than the non-Speech Pathology undergraduates. While Speech Pathology graduate students tended to rate the four tapes as being more fluent than did the Pre-professional Speech Pathology students, only one tape was rated significantly different.     

The layman's use of trait and behavioral information to predict behavior

This study investigated conditions that determine subjects' preferences for information about another person's traits versus his specific past behavior in order to predict his future behavior. The similarity-dissimilarity between the situation for which past behavior was available and the one to which predictions had to be made strongly influenced the choice of specific behavioral information versus more general trait information. As expected, behavioral information was preferred most when the situation to which behavior had to be predicted was highly similar to the one for which the past behavioral data were available. On the other hand, more general trait information was preferred in predicting to situations that were not directly similar to those for which past behavioral information was available. The effect of the temporal span covered by available information was also explored.     

The effect of perceived distance on perceived movement

Equations were developed to predict the apparent motion of a physically stationary object resulting from head movement as a function of errors in the perceived distances of the object or of its parts. These equations, which specify the apparent motion in terms of relative and common components, were applied to the results of two experiments. In the experiments, the perceived slant of an object was varied with respect to its physical slant by means of perspective cues. In Experiment I, O reported the apparent motion and apparent distance of each end of the object independently. The results are consistent with the equations in terms of apparent relative motion, but not in terms of apparent common motion. The latter results are attributed to the tendency for apparent relative motion to dominate apparent common motion when both are present simultaneously. In Experiment II, a direct report of apparent relative motion (in this case, apparent rotation) was obtained for illusory slants of a physically frontoparallel object. It was found that apparent rotations in the predicted direction occurred as a result of head motion, even though under these conditions no rotary motion was present on the retina.     

Changes in factor structure of a complex psychomotor test as a function of practice

Scores obtained at eight different stages of practice on the Complex Coordination Test together with scores on 18 reference tests were subjected to a Thurstone Centroid Factor Analysis. Nine meaningful factors were identified in the experimental battery. The results indicated considerable, but systematic, changes in the factor structure of the Complex Coordination Test as practice on the task was continued. The test became less complex (factorially) as practice was continued. Moreover, there was a change in thenature of the factors contributing variance at early and later stages of practice. Implications of the findings are related to certain problems of learning theory, psychomotor test development, and criterion analysis. Skill Components Research Laboratory. The opinions or conclusions contained in this report are those of the authors and do not necessarily reflect the views or indorsement of the Department of the Air Force. The writers are indebted to Dr. Jack A. Adams for the basic data on which this analysis is based.