Summary: Research Article
The Capacity of Visual Short-
Term Memory Is Set Both by
Visual Information Load and
by Number of Objects
G.A. Alvarez and P. Cavanagh
Harvard University
ABSTRACT--Previous research has suggested that visual short-
term memory has a fixed capacity of about four objects. How-
ever, we found that capacity varied substantially across the five
stimulus classes we examined, ranging from 1.6 for shaded
cubes to 4.4 for colors (estimated using a change detection task).
We also estimated the information load per item in each class,
using visual search rate. The changes we measured in memory
capacity across classes were almost exactly mirrored by changes
in the opposite direction in visual search rate (r2
5 .992 between
search rate and the reciprocal of memory capacity). The greater
the information load of each item in a stimulus class (as in-
dicated by a slower search rate), the fewer items from that class

Source: Alvarez, George A. - Department of Psychology, Harvard University
Cavanagh, Patrick - Department of Psychology, Harvard University

Collections: Biology and Medicine