The contributions of pictorial, motion, and binocular cues to the perception of depth and distance

Multiple visual cues are available for the estimation of distance. According to the modified weak fusion model, the information from these cues is combined through weighted averaging, with the weights determined by the relative reliability of each cue. Empirical tests of this model tend to isolate a small number of cues, in order for their reliabilities to be manipulated. Weights measured in this way are specific to the testing environment, and do not allow us to quantify the contributions of individual cues in natural viewing. To address this, we used estimates from the literature of sensitivity for a wide range of distance cues to predict the contribution of pictorial, binocular, and motion cues to relative distance. The cues assessed included convergence, accommodation, height in the field, texture density, relative size, height in the field, binocular disparity, and motion (assuming a walking observer). We used the modified weak fusion model to estimate the contribution of binocular, motion, and pictorial cues for distances between 2 and 100 m. These calculations provide estimates of the expected contributions of individual depth cues in everyday viewing conditions. In most cases, our results show a clear benefit for the weighted averaging of cues in the natural environment, in comparison with the use of the most reliable cue alone.