Aging and the perception of depth and 3-D shape from motion parallax

The ability of younger and older observers to perceive 3-D shape and depth from motion parallax was investigated. In Experiment 1, the observers discriminated among differently curved 3-dimensional (3-D) surfaces in the presence of noise. In Experiment 2, the surfaces' shape was held constant and the amount of front-to-back depth was varied; the observers estimated the amount of depth they perceived. The effects of age were strongly task dependent. The younger observers' performance in Experiment 1 was almost 60% higher than that of the older observers. In contrast, no age effect was obtained in Experiment 2. Older observers can effectively perceive variations in depth from patterns of motion parallax, but their ability to discriminate 3-D shape is significantly compromised.