Failure of familiar size to determine a metric for visually perceived distance

The use of knowledge of the familiar sizes of objects in determining the apparent distances of those objects is known as the familiar size cue to distance. If effective, this cue might be one of the factors responsible for supplying the metric (scalar) characteristics of perceptions of spatial extent within a visual display in which other information concerning scalar extents has been reduced to a minimum. Two groups of observers were presented with realistic objects of the same angular, but different assumed, sizes presented in such a cue-restricted display. Perceptions of size and distance within the display did not differ significantly as a function of the type of object initially presented. This result was consistent with the notion that scalar perceptions under these conditions probably are determined by a factor known as the specific distance tendency, rather than by the experiential factor of familiar size.     

Testing a linear relation between true scores of two measures

We concern ourselves with the hypothesis that two variables have a perfect disattenuated correlation, hence measure the same trait except for errors of measurement. This hypothesis is equivalent to saying, within the adopted model, that true scores of two psychological tests satisfy a perfect linear relation. Statistical tests of this hypothesis are derived when the relation is specified with the exception of the additive constant. Two approaches are presented and various assumptions concerning the error parameters are used. Then the results are reinterpreted in terms of the possible existence of an unspecified perfect linear relation between true scores of two psychological tests. A numerical example is appended by way of illustration. Research reported in this paper has been supported by grant GB-18230 from National Science Foundation.     

On the theory of a set of tests which differ only in length

This paper presents a contribution to the sampling theory of a set of homogeneous tests which differ only in length, test length being regarded as an essential test parameter. Observed variance-covariance matrices of such measurements are taken to follow a Wishart distribution. The familiar true score-and-error concept of classical test theory is employed. Upon formulation of the basic model it is shown that in a combination of such tests forming a “total” test, the singal-to-noise ratio of the components is additive and that the inverse of the population variance-covariance matrix of the component measures has all of its off-diagonal elements equal, regardless of distributional assumptions. This fact facilitates the subsequent derivation of a statistical sampling theory, there being at mostm + 1 free parameters whenm is the number of component tests. In developing the theory, the cases of known and unknown test lengths are treated separately. For both cases maximum-likelihood estimators of the relevant parameters are derived. It is argued that the resulting formulas will remain resonable even if the distributional assumptions are too narrow. Under these assumptions, however, maximum-likelihood ratio tests of the validity of the model and of hypotheses concerning reliability and standard error of measurement of the total test are given. It is shown in each case that the maximum-likelihood equations possess precisely one acceptable solution under rather natural conditions. Application of the methods can be effected without the use of a computer. Two numerical examples are appended by way of illustration. This research was supported in part by The National Institute of Child Health and Human Development, under Research Grant 1 PO1 HDO1762.     

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.