Adaptation in distance perception based on oculomotor cues

Accommodation and convergence primarily serve to adjust the eyes to the distance of the object viewed, but, once made, these oculomotor adjustments serve as cues for the object’s distance. Experiments are reported that show that the relation between oculomotor adjustments and the distances they signify can be changed by adaptation to glasses that cause alteration in the oculomotor adjustments with which objects are viewed. This changed relation manifested itself in marked alterations of size perception. Wearing, for 30 min, glasses that caused a change in accommodation and convergence corresponding to a smaller object distance and equivalent to 1.5 lens diopters caused subsequent mean size increases that ranged from 50% to 65%. Adaptation to glasses that changed oculomotor adjustments in the same amount but in the opposite direction resulted in decreases in perceived sizes that varied from 18% to 40%, dependent on the distance of the test object. These were the results of size estimates obtained before and after the adaptation period under conditions where only accommodation and convergence served as cues for distance. A newly developed test of size perception was also used, in which S adjusted the size of the projected image of an array of familiar objects on a screen until the size of the objects appeared normal. Again, such adjustments were made before and after the adaptation period, and size differences were obtained that were in the direction to be expected of adaptation and varied in amount between 12% and 33%, dependent on the distance of the screen. The reason for the different amounts of size change measured by the two kinds of tests was investigated.     

Effects of inferiority and superiority in groups on recognition memory and confidence

Summary Three dependent variables were derived from an extended Signal-Detection paradigm: memory performance, confidence level, and response-bias. In the assessment of memory items, S and 2 confederates were exposed periodically to fictitious results which implied inferiority or superiority of S. Memory performance was generally better in group situations than when the subject was alone. Within groups, inferiority motivated S to improve. Significant confidence differences between correct and false judgments and, if S judged falsely, a high susceptibility to cognitions about S's relative performance, led theoretically to a distinction between internal and external cues and to the assumption that S wished to avoid uncertainty. Response-bias was found to be independent of motivation and very close to expected stimulus occurrence. The reward/cost theory of Thibaut and Kelley accounts for the motivation engendered and is linked to some theoretical considerations about processing objectively classifiable stimuli in social context.

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Zusammenfassung Aus einem erweiterten Signal-Detection-Paradigma wurden 3 abhängige Variablen abgeleitet: Gedächtnisleistung, Sicherheitsniveau und Response-bias. Bei der Beurteilung von Gedächtnisaufgaben wurden einer Vp und 2 Mitwissern des Vl von Zeit zu Zeit fiktive Ergebnisse gezeigt, die entweder Unterlegenheit oder Überlegenheit der Vp induzierten. Verglichen mit einer Alleinsituation stieg die Gedächtnisleistung allgemein in Gruppensituationen. Innerhalb von Gruppensituationen wurde die Vp durch Unterlegenheit motiviert, sich zu verbessern. Signifikante Unterschiede in der Sicherheit zwischen richtigen und falschen Urteilen und hohe Beeinflußbarkeit durch Kognitionen über den relativen Leistungsstand der Vp bei Fehlerurteilen führte theoretisch zu einer Unterscheidung zwischen innerem und äußerem Aufschluß und zu der Annahme, daß die Vp Unsicherheit vermeiden will. Der gefundene Response-bias war unabhängig von Motivation und sehr nahe bei der Wahrscheinlichkeit des Auftretens der Reize. Die reward/cost Theorie von Thibaut und Kelley kann die erzeugte Motivation erklären und wird mit einigen theoretischen Überlegungen über die Verarbeitung objektiv definierbarer Reize im sozialen Kontext verknüpft.

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This research was supported by research grants from the Deutsche Forschungsgemeinschaft allotted to the Sonderforschungsbereich 24 at the University of Mannheim, West Germany. We are grateful to Mary Madden, Pauline Sadler, and Jennifer S. Sentance for their cooperation on the English translation.

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This article is partly based on a Diplom-thesis by the second author entitled Effekte von Überlegenheit und Unterlegenheit in Gruppen auf Gedächtnisleistung und Skalengebrauch.     

Negation of Park's transformations

Zusammenfassung Parks Kritik beruht, meiner Ansicht nach, auf einem entscheidenden Mißverständnis meiner Intentionen: es geht mir überhaupt nicht um eine Argumentation gegen eine Transformationsgrammatik à la Chomsky, und nicht einmal in erster Linie gegen die Absicht mancher Psycholinguisten, eine derartige Theorie in ihren psychischen Funktionen aufzuzeigen. Ich möchte lediglich dafür plädieren, daß die Psycholinguistik in erster Linie psychologische (und nicht linguistische) Überlegungen und Modellvorstellungen als Leitlinien verwendet.     

The effect of abnormal displacement of the retinal image during eye movements

The displacement of the images on the retina that results from a turning of the eye does not lead to an apparent motion of what is seen, It has been generally assumed that this is due to a compensating process which takes eye movement into account and serves to discount those image displacements that result from eye movements, It follows from this view that an abnormal image displacement, that is, an image displacement that is larger or smaller than the causing eye movement would warrant, should lead to an experienced displacement of the target. Abnormal image displacement was produced by placing the eye in the converging or diverging bundle of rays from a point source that form behind a strong positive lens; this arrangement yielded a disc-shaped image, the projection of the pupil onto the retina, which displaced abnormally during eye movements. By changing the position of the eye along the axis of the lens in relation to the crossing point of the bundle, the degree to which the displacement was abnormal could be varied, For various displacement rates ranging from 25% to 120 and 400% of normal, abnormal displacements produced by incidental eye movements remained unnoticed, Only where eye movements were intentional did some of our Ss report shifts of the perceived image. It is suggested that the organism copes with the image displacement resulting from the ever-present incidental eye movements not by compensation but by ignoring them.     

Can a shuttlebox computer analog be used to condition human avoidance behavior?

Freedman (1990) introduced a computer analog of the shuttlebox paradigm and presented results to show that this analog could be used for studying human avoidance conditioning. In the present study, a first experimental phase was conducted to test how the fact that the tone was considered aversive in the instructions and the intensity of this tone affect avoidance behavior. In a transfer-of-control test phase, it was tested as to whether the warning stimulus presented as a cue to the aversive stimulus had acquired either aversive or informative quality. An effect of instructions was observed for both levels of the auditive stimulus, and a stimulus effect was found for those groups that were given the instructions that described the tone as aversive. In the case of subjects who in the first phase achieved a certain learning criterion, it was recorded how often they in the second phase selected a condition in which the warning signal of the first phase was not presented. No transfer of control was observed. Thus, no positive evidence was found indicating that Freedman’s computer analog could be used for studying human avoidance conditioning.     

An extension of the concept of specific objectivity

Comparisons of subjects are specifically objective if they do not depend on the items involved. Such comparisons are not restricted to the 1-parameter logistic latent trait model, but may also be defined within ordinal independence models and even within the 2-parameter logistic model.     

How valid is the psychoticism scale? A comment on the Van Kampen critique

Van Kampen (1993) has published a paper in which he criticizes the concept of psychoticism and the use of the P scale as a measuring device, and advances measures for his own S scale and its validity. This reply attempts to clarify the notion of ‘validity’, and to demonstrate that there is a considerable body of experimental evidence to show that P has a high degree of construct validity, whereas the Van Kampen S scale lacks completely any degree of construct validity. Several examples are given of how the experimental evidence legitimates both the P scale, and the theory (nomological network) on which it is based.     

A compensatory approach to optimal selection with mastery scores

A Bayesian approach for simultaneous optimization of test-based decisions is presented using the example of a selection decision for a treatment followed by a mastery decision. A distinction is made between weak and strong rules where, as opposed to strong rules, weak rules use prior test scores as collateral data. Conditions for monotonicity of optimal weak and strong rules are presented. It is shown that under mild conditions on the test score distributions and utility functions, weak rules are always compensatory by nature. The authors are indebted to Wilbert Kallenberg for his valuable comments and to Jan Gulmans for providing the data for the empirical example. The names of the authors are alphabetical; they are equally responsible for the contents of this paper.     

Validation of a full body 3-D dynamic linked segment model

In studies related to human movement, linked segment models (LSM's) are often used to quantify forces and torques, generated in body joints. Some LSM's represent only a few body segments. Others, for instance used in studies on the control of whole body movements, include all body segments. As a consequence of the complexity of 3-dimensional (3-D) analyses, most LSM's are restricted to one plane of motion. However, in asymmetric movements this may result in a loss of relevant information. The aim of the current study was to develop and validate a 3-D LSM including all body segments. Braces with markers, attached to all body segments, were used to record the body movements. The validation of the model was accomplished by comparing the measured with the estimated ground reaction force and by comparing the torques at the lumbo-sacral joint that resulted from a bottom-up and a top-down mechanical analysis. For both comparisons, reasonable to good agreement was found. Sources of error that could not be analysed this way, were subjected to an additional sensitivity analysis. It was concluded that the internal validity of the current model is quite satisfactory.