Resolving discrepant results of the Wheatstone Experiment

Summary Soon after Wheatstone published his results obtained with the twelve earliest stereograms. Brewster disputed the result obtained with one of them. This stereogram consisted of a thick vertical line presented to one eye and a thin vertical and thick inclined line to the other. Wheatstone reported seeing depth with this figure but Brewster did not. We conducted three experiments to explore the possible reason for the disagreement. Experiment 1 indicated that the stereogram produces a variety of perceptions including the depth as reported by Wheatstone and the rivalry as reported by Brewster. Experiment 2 showed that Brewster's procedure of keeping the eyes fixed while viewing the stereogram reduces the proportion of subjects reporting depth. In Experiment 3, the top half and the bottom half of the stereogram were presented in different trials. The top of the stereogram that contains no conflicting cues produced reliable depth, but the bottom that does, did not. It is concluded that the difference in the procedures they used and the nature of the stimulus were responsible for the conflicting results.     

Orientation effects on line afterimages

Lines of various orientations were viewed as prolonged afterimages in six experiments. The duration of unitary appearance was not influenced by line orientation for monocular afterimages, but there was a marginal effect for afterimages generated binocularly; vertical and horizontal lines tended to be visible for longer than did 45-deg lines. Measures of fragmentation frequency and the latency to the first disappearance did not vary reliably with orientation under any conditions. Binocular afterimages lasted longer than did monocular ones, but generally showed the same pattern of fragmentations. These results are compared with those from experiments using optical stabilization and steady fixation, in which orientation differences have been reported.     

The influence of eye movements and eye position on perception of the visual vertical

Summary Four experiments are reported which involved the adjustment of two points of light in an otherwise dark room to the visual vertical. In the first two experiments different point separations (corresponding to visual angles of about 2° and 23°) were employed in an attempt to control the degree of scanning eye movements. Binocular adjustments to the visual vertical during body tilt were influenced by the point separation (Exp. 1), but monocular adjustments with the head upright were not (Exp. 2). Using the larger point separation and fixating the top point the visual vertical using the right eye was counterclockwise of that with fixation of the bottom point when the head was upright (Exp. 3), but this difference was not found for judgments during tilt (Exp. 4). The results were discussed in terms of the rotational changes in eye position accompanying scanning eye movements and ocular elevation and depression.

---

Zusammenfassung Es wird über vier Experimente berichtet, in denen es um die Einstellungen zweier Lichtpunkte in eine vertikale Richtung geht. In den ersten zwei Experimenten sollte der Einfluß der Fixierbewegungen der Augen geprüft werden. Der Winkelabstand der Lichtpunkte betrug 2° oder 23°. Bei seitwärts geneigtem Körper und binokularer Betrachtung wurde ein Unterschied gefunden (Exp. 1). Bei aufrecht gehaltenem Kopf und monokularer Betrachtung dagegen zeigte sich kein Unterschied (Exp. 2). Wurde in aufrechter Körperlage und bei einem Punktabstand von 23° der obere Punkt mit dem rechten Auge fixiert, so verschob sich die scheinbare Vertikale im Uhrzeigersinn; sie verschob sich noch weiter im Uhrzeigersinn, wenn der untere Punkt fixiert wurde (Exp. 3). Bei geneigtem Körper wurde dagegen kein Unterschied festgestellt (Exp. 4). Die Ergebnisse werden im Zusammenhang mit der Augendrehung diskutiert, die mit dem scanning sowie mit der Auf- und Abbewegung der Augen beim Fixieren verbunden ist.

---

---

This research was carried out while I was a recipient of a Forschungsstipendium from the Alexander von Humboldt-Stiftung, appreciation for which is gratefully acknowledged. I also wish to thank the subjects who participated in the experiments.     

Bain on Neural Networks

In his bookMind and body(1873), Bain set out an account in which he related the processes of associative memory to the distribution of activity in neural groupings—or neural networks as they are now termed. In the course of this account, Bain anticipated certain aspects of connectionist ideas that are normally attributed to 20th-century authors—most notably Hebb (1949). In this paper we reproduce Bain's arguments relating neural activity to the workings of associative memory which include an early version of the principles enshrined in Hebb's neurophysiological postulate. Nonetheless, despite their prescience, these specific contributions to the connectionist case have been almost entirely ignored. Eventually, Bain came to doubt the practicality of his own arguments and, in so doing, he seems to have ensured that his ideas concerning neural groupings exerted little or no influence on the subsequent course of theorizing in this area.     

African American men's Gender Role Conflict: The significance of racial identity

This study examined the relationships between racial identity attitudes and gender role conflict in a sample of 95 African American men ages 23–80 years old. Participants completed the 1981 Black Racial Identity Attitude Scale by Parham and Helms and the 1986 Gender Role Conflict Scale by O'Neil, Helms, Gable, David, and Wrightsman. Results indicated that racial identity attitudes were differentially related to patterns of gender role conflict when racial identity is externally defined. However, an internally defined racial identity had no relationship to gender role conflict. Results are discussed in terms of the significance of racial identity for understanding African American men's conflict associated with traditional male gender role standards and expectations.     

It's the thought that counts: specific brain regions for one component of theory of mind

Evidence from developmental psychology suggests that representing the contents of other people's thoughts and beliefs depends on a component of reasoning about other minds (theory of mind) that is distinct from the earlier-developing mental-state concepts for goals, perceptions, and feelings. To provide converging evidence, the current study investigated the substrate of the late-developing process in adult brains. Three regions--the right and left temporo-parietal junction and the posterior cingulate--responded selectively when subjects read about a protagonist's thoughts, but not when they read about other subjective, internal states or other socially relevant information about a person. By contrast, the medial prefrontal cortex responded equivalently in all of these story conditions, a result consistent with a broader role for medial prefrontal cortex in general social cognition. These data support the hypothesis that the early- and late-developing components of theory of mind rely on separate psychological and neural mechanisms, and that these mechanisms remain distinct into adulthood.