Elizabeth Johnston

Systematic distortions of shape from stereopsis.

The effectiveness of disparity information in defining 3-D shape was investigated by means of judgements of the shape of cylindrical continuous curved surfaces presented as random dot stereograms. At a close viewing distance, truly circular cylinders appeared elongated; at an intermediate distance, perception was close to veridical; and, at a far distance, cylinders appeared flattened. Indirect measures of scaling distance were calculated from these data. The results strongly suggest that the observed shape distortions are a consequence of scaling horizontal disparities with an incorrect measure of egocentric distance.

Integration of Stereopsis and Motion Shape Cues

A global shape judgement task was used to investigate the combination of stereopsis and kinetic depth. With both cues present, there were no distortions of shape perception, even under conditions where either cue alone did show such distortions. We suggest that the addition of motion information overcomes the stereo distance scaling problem. However, when incongruent combinations of disparity and motion were used, the results did not match predictions of a number of combination theories. These data could be described by a model which used weighted linear combination after correctly scaling disparities for viewing distance. When the motion cue was weakened by presenting only two frames of each motion sequence, stereo was weighted more heavily.

Integration of depth modules: Stereopsis and texture

Global shape judgements were employed to examine the combination of stereopsis and shape-from-texture in the determination of three-dimensional shape. Adding textural variations to stereograms increased perceived depth. Thus, texture was not simply vetoed by the strong stereo cue. In experiments where the depth specified by texture was incongruent with that specified by stereo, the data were well described by a weighted linear combination rule. Although only a small weight was assigned to texture, this weight was somewhat greater at a farther viewing distance. This could be a consequence of the decreased reliability of stereopsis at far viewing distances.

Effects of different texture cues on curved surfaces viewed stereoscopically.

Stereoscopic shape judgements can be modified by the addition of texture cues. This paper examines the properties of texture that are responsible for this effect. When a three-dimensional curved surface is projected onto a two-dimensional image, changes in surface orientation result in gradients of texture element size (or area), shape (compression) and density in the image. Manipulating each of these gradients independently we found that 97% of the variance in the results could be accounted for by the compression gradient. When the texture pattern corresponds to a highly anisotropic texture on the objects surface, shape-from-texture becomes ineffective. These results suggest that human shape-from-texture proceeds under the assumption that textures are statistically isotropic, and not that they are homogeneous.

Balancing life and work by unbending gender: Early American women psychologists’ struggles and contributions

Womens participation in the work force shifted markedly throughout the twentieth century, from a low of 21 percent in 1900 to 59 percent in 1998. The influx of women into market work, particularly married women with children, put pressure on the ideology of domesticity: an ideal male worker in the outside market married to a woman taking care of children and home (Williams, 2000). Here, we examine some moments in the early-to-mid-twentieth century when female psychologists contested established norms of life-work balance premised on domesticity. In the 1920s, Ethel Puffer Howes, one of the first generation of American women psychologists studied by Scarborough and Furumoto (1987), challenged the waste of womens higher education represented by the denial of their interests outside of the confines of domesticity with pioneering applied research on communitarian solutions to life-work balance. Prominent second-generation psychologists, such as Leta Hollingworth, Lillian Gilbreth, and Florence Goodenough, sounded notes of dissent in a variety of forums in the interwar period. At mid-century, the exclusion of women psychologists from war work galvanized more organized efforts to address their status and life-work balance. Examination of the ensuing uneasy collaboration between psychologist and library scholar Alice Bryan and the influential male gatekeeper E. G. Boring documents gendered disparities in life-work balance and illuminates how the entrenched ideology of domesticity was sustained. We conclude with Jane Loevingers mid-century challenge to domesticity and mother-blaming through her questioning of Borings persistent focus on the need for job concentration in professional psychologists and development of a novel research focus on mothering.

Assessing Pragmatic Skills in Children's Language.

The purpose of this article is to provide the speech-language pathologist with information regarding the assessment of pragmatic skills in childrens language. The authors delineate the most freque...