Monkey visual short-term memory directly compared to humans

Two adult rhesus monkeys were trained to detect which item in an array of memory items had changed using the same stimuli, viewing times, and delays as used with humans. Although the monkeys were extensively trained, they were less accurate than humans with the same array sizes (2, 4, & 6 items), with both stimulus types (colored squares, clip art), and showed calculated memory capacities of about 1 item (or less). Nevertheless, the memory results from both monkeys and humans for both stimulus types were well characterized by the inverse power-law of display size. This characterization provides a simple and straightforward summary of a fundamental process of visual short-term memory (STM; how VSTM declines with memory load) that emphasizes species similarities based upon similar functional relationships. By more closely matching monkey testing parameters to those of humans, the similar functional relationships strengthen the evidence suggesting similar processes underlying monkey and human VSTM.