Various visual cues provide information about depth and shape in a scene. When several of these cues are simultaneously available in a single location in the scene, the visual system attempts to combine them. In this paper, we discuss three key issues relevant to the experimental analysis of depth cue combination in human vision: cue promotion, dynamic weighting of cues, and robustness of cue combination. We review recent psychophysical studies of human depth cue combination in light of these issues. We organize the discussion and review as the development of a model of the depth cue combination process termed modified weak fusion (MWF). We relate the MWF framework to Bayesian theories of cue combination. We argue that the MWF model is consistent with previous experimental results and is a parsimonious summary of these results. While the MWF model is motivated by normative considerations, it is primarily intended to guide experimental analysis of depth cue combination in human vision. We describe experimental methods, analogous to perturbation analysis, that permit us to analyze depth cue combination in novel ways. In particular these methods allow us to investigate the key issues we have raised. We summarize recent experimental tests of the MWF framework that use these methods.

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A global shape judgement task was used to investigate the combination of stereopsis and kinetic depth. With botb 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 afier 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.

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.

Objective: Data from the 1995 Nova Scotia Health Survey were analyzed to determine the relation between body mass index (BMI) and the risk of depression as measured by the Center for Epidemiological Studies Depression Scale (CES-D).Methods: Clinical measures for height and weight and CES-D scores were available for 2,482 subjects from an initial sample of 5,578 Nova Scotians stratified probabilistically to be representative of age, gender and area of residence. BMIs were categorized according to the international standards (BMI 18.5-24.9 acceptable weight; 25-29.9 overweight; 30 obese).Results: More men than women were classified as overweight (43.2% vs. 28.3%) but slightly more women than men were obese (25.6% vs. 23.4%). Based on the summary score of the CES-D, 14.2% were categorized as at risk for depression ( 16). Logistic regression indicated that lower education (p<0.001) and income (p<0.001), and BMI category (p<0.05) were all significantly related to an increased risk of depression. The odds ratio for the association between obesity and depression, after controlling for education and income, was 1.41 [95% CI = 1.07-1.86].Discussion: More studies are needed to ascertain the mechanism by which obesity and depression could be related and the significance of this relation for the prevention and treatment of both obesity and depression. Given the effects of depression, we suggest that health professionals should assess their obese patients for risk of depression before embarking on a weight management protocol.La traduction du résumé se trouve à la fin de l'article.