A signal-to-noise theory of the effects of luminance on picture memory: comment on Loftus.

In studies of picture memory, subjects typically view a sequence of pictures. Their memory is tested either after each picture is presented (short-term recall) or at the end of the sequence (long-term recall). The increase in performance as a function of picture viewing time defines "the rate of information acquisition." Loftus (1985) found that reducing the luminance of a picture reduces the rate at which information is acquired (for both short-term and long-term tests) and, for long viewing times, reduces the total amount of recall. The theory proposed here assumes that both of these effects are consequences of intrinsic noise in the visual system that becomes relatively more prominent as signal (picture luminance or contrast) is reduced. Noise shares a limited capacity channel with signal, and thus noise reduces the rate of information acquisition; noise, as well as signal, occupies space in memory, and thus noise reduces recall performance.