SERIAL-LEARNING BY RHESUS-MONKEYS .1. ACQUISITION AND RETENTION OF MULTIPLE 4-ITEM LISTS

Two rhesus monkeys were trained to learn eight 4-item lists, each composed of 4 different photographs. Lists were trained in successive phases: A, A --> B, A --> B --> C, and A --> B --> C --> D. After List 4, retention, as measured by the method of savings, was, on average, 66% (range: 44-84%). Indeed, all 4 lists could be recalled reliably during a single session with neither a decrement in accuracy nor an increase in the latency of responding to each item. Response latencies on a subset test employing all possible 2- and 3-item subsets of each 4-item list support the hypothesis that monkeys form linear representations of a list. Latencies to Item 1 of a subset varied directly with the position of that item in the original list. On List 1, latencies to Item 2 varied directly with the number of intervening items between Item 1 and Item 2 in the original list. During the acquisition of Lists 5-8, both Ss mastered the A --> B and A --> B --> C phases of training in the minimum number of trials possible.