THE CONTRIBUTION OF COLOR TO VISUAL MEMORY IN X-CHROMOSOME-LINKED DICHROMATS

We used a recognition memory paradigm to assess the visual memory of X -chromosome-linked dichromats for color images of natural scenes. The performance of 17 protanopes and 14 deuteranopes, who lack the second (red-green opponent) subsystem of color vision, but retain the primord ial (yellow-blue opponent) subsystem, was compared with that of 36 col or normal observers. During the presentation phase, 48 images of natur al scenes were displayed on a CRT for durations between 50 and 1000 ms ec. Each image was followed by a random noise mask. Half of the images were presented in color and half in black and white. In the subsequen t query phase, the same 48 images were intermixed with 48 new images a nd the subjects had to indicate which of the images they had already s een during the presentation phase. We find that the performance of the color normal observers increases,vith exposure duration. However, the y perform 5-10% better for colored than for black and white images, ev en at exposure durations as short as 50 msec. Surprisingly, performanc e is not impaired for the dichromats, whose recognition performance is also better for colored than for black and white images. We conclude either that X-chromosome-linked dichromats may be able to compensate f or their reduced chromatic information range when viewing complex natu ral scenes or that the chromatic information in most natural scenes, f or the durations tested, is sufficiently represented by the surviving primordial color subsystem. (C) 1998 Elsevier Science Ltd. All rights reserved.