Homonymy in the Lexicons of Young Children Acquiring American Sign Language

The incidence of homonymy in children's early sign language production was examined in nine young children of deaf parents. Analysis of parental reports of how their children formed their signs revealed that all of the children produced homonymous forms (i.e., a single manual form used to represent two or more different adult target signs). Altogether, the children were reported as producing 26 sets of homonymous forms to represent 59 adult target signs. This incidence of homonymy in the children's early signing did not differ significantly from the incidence of homonymy previously reported in a study of normally developing children acquiring spoken language. This finding is interpreted as indicating an important similarity in language acquisition processes across language modalities. Analysis of the sign formational characteristics of the children's homonymous forms revealed that the children's signs and the adult target signs typically shared a common location aspect. The movement and handshape aspects of the adult target signs were less frequently retained in the children's homonymous forms.     

Withdrawing attention at little or no cost: Detection and discrimination tasks

We used a concurrent-task paradigm to investigate the attentional cost of simple visual tasks. As in earlier studies, we found that detecting a unique orientation in an array of oriented elements (“pop-out”) carries little or no attentional cost. Surprisingly, this is true at all levels of performance and holds even when pop-out is barely discriminable. We discuss this finding in the context of our previous report that the attentional cost of stimulus detection is strongly influenced by the presence and nature of other stimuli in the display (Braun, 1994b). For discrimination tasks, we obtained a similarly mixed outcome: Discrimination of letter shape carried a high attentional cost whereas discrimination of color and orientation did not. Taken together, these findings lead us to modify our earlier position on the attentional costs of detection and discrimination tasks (Sagi & Julesz, 1985). We now believe that observers enjoy a significant degree of “ambient” visual awareness outside the focus of attention, permitting them to both detect and discriminate certain visual information. We hypothesize that the information in question is selected by a competition for saliency at the level of early vision.     

Visual attention and perceptual grouping.

Perceptual organization is thought to involve an analysis of both textural discontinuities and perceptual grouping. In earlier work, we found that textural discontinuities were detected normally even when visual attention was engaged elsewhere. Here we report how perceptual grouping is affected when visual attention is engaged by a concurrent visual task. To elicit perceptual grouping, we used the Gestalt demonstrations of grouping on the basis of proximity and of similarity. Four tasks were investigated, some requiring the observer to discriminate between horizontal and vertical grouping, and some requiring the observer to merely detect the presence or absence of grouping. Visual attention was engaged at the center of the display by a form identification task. The detection of a textural discontinuity served as a control task. Concurrent form identification conflicted with all four grouping tasks, resulting in a significant reduction of grouping performance in each case. No performance reduction was observed when either form identification or grouping discrimination was combined with the detection of a textural discontinuity. These results suggest that perceptual grouping and form identification compete for visual attention, whereas the detection of a textural discontinuity does not.     

Short-term retention of superimposed and of spatially distinct multiletter visual arrays

On each trial, Ss attempted to retain a series of five visually presented letters while concurrently “shadowing” (repeating aloud) a rapid series of aurally presented letters. If serial-position accuracy is ignored, they were able to store more than only the last letter of a typical series, even though all five letters appeared on the same screen, and that performance was superior to the retention of five auditorily presented letters. Together, these findings suggest that a form of visual storage might have been employed for the retention of visual stimuli and, specifically, one that was relatively immune to erasure as compared to “iconic” storage. In further support of that hypothesis, retention of such visual series as measured by free-recall accuracy was not inferior to that of five letters, each of which was presented on a separate screen.