Visual detectability gradients: the effect of distractors in contralateral field

A number of studies involving recognition of tachistoscopically presented words have reported that the typical right visual field performance superiority associated with linguistic stimuli is enhanced by bilateral presentations (simultaneous stimuli in both visual half-fields) compared to unilateral presentations (stimuli in only one half-field on a trial). We have reported the same phenomenon, however, using visual spatial patterns in a search paradigm (E. W. Yund, R. Efron, & D. R. Nichols, 1990c. Brain and Cognition, 12, 117-127) and have accounted for it in terms of the operating characteristics of a visual scanning mechanism which serially examines a decaying neural representation of the stimuli. In the present experiment we attempted to exploit these operating characteristics to influence this difference between unilateral and bilateral presentations. The results not only are consistent with the assumptions of the scanning hypothesis but they also provide new information pertinent to the operating characteristics of this mechanism.     

Target detection in one visual field in the presence or absence of stimuli in the contralateral field by right- and left-handed subjects

Marked differences in detectability are observed as a function of retinal locus when subjects are required to find a briefly exposed target pattern of uncertain location in the presence of a number of discriminably different nontarget patterns. Our previous studies using this search paradigm have attributed these detectability differences, and the right visual field detectability superiority associated with them, to a serial (scanning) mechanism which tends to examine stimuli in the right field earlier than those in the left. The present experiment, performed on large groups of right- and left-handed subjects, was designed to test the hypothesis that there are two independent serial processors, one in each hemisphere--an hypothesis which might account for the differences in detectability within and between the two half-fields in terms of hemispheric processing differences. The results are inconsistent with the dual independent serial processor hypothesis but are fully consistent with a single serial processor, a scanning mechanism, which has access to the information presented to both visual half-fields.     

Yosef Hayim Yerushalmi: Historian of German Jewry

This article draws attention to a rarely considered dimension of Yosef Hayim Yerushalmi’s scholarship and teaching, namely, his engagement with the history of German Jewry. It examines the manner in which Yerushalmi approached this subject—generally through the twin poles of antisemitism and Wissenschaft des Judentums—and suggests that analyzing it with reference to the Arendtian categories of “pariah” and “parvenu” provides us with a key to unlocking some of the motivations that drove Yerushalmi’s particular interests. The article concludes with some speculation as to why, by contrast, Yerushalmi seemed to avoid the history of Eastern European Jewry, in spite of his oft-repeated pride in and intimacy with his own personal heritage.     

Detectability gradients as a function of target location

We examined the ability to detect a specified visual pattern (a target) in a randomly selected location when it was briefly presented with 11 other spatially distributed nontarget patterns and also when it was presented by itself for the same duration (50 msec) on a background of visual noise. Two experiments were designed to measure target detectability as a function of its location in the visual field where all possible target locations were equidistant from the fovea. A right visual field detection superiority was obtained in both experiments. In addition, highly significant detectability differences were observed within the right and left visual fields in both experiments. The origin of these detectability differences are interpreted in terms of parallel and serial processing mechanisms.