Herbert S. Terrace, director
Here is a brief list of some recently completed experiments. Click on the experiment name for more info. MetaMTSS (using confidence judgements) Hint Simchain Simchain
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The ability to make judgements on one's own knowledge is called metacognition, and for a long time was thought to be a uniquely human ability. In this experiment, we looked for evidence of metacognition in monkeys by devising a paradigm where they could make confidence judgements on their performance on a variety of tasks. We started with psychophysical tasks, such as identifying the longest line in an array. Then we used a working memory task (matching to successive sample), where the monkeys saw a series of pictures and then had to choose the familiar one from an array of pictures (only one of which they had actually seen before). Before finding out if they were right or wrong, the monkeys made a confidence judgement, or a "bet". If they chose high risk, they would earn 3 tokens following a correct response, and lose 3 tokens following and incorrect response. If they chose low risk, though, they were guaranteed one token. Each time the monkey accumulated a certain amount of tokens, they were given a food reward.
The results of this experiment will be published in Psychological Science in early 2007. For a video of Ebbinghaus doing this task, go to Videos.
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Sequences contain two types of information, order and item information. The simultaneous chaining paradigm has already proven that monkeys are capable of remembering both types of information in long-term memory. However, studies looking at short term memory have yet to prove that monkeys can remember both. Individually, item information and order information has been proven for short term memory but whether the monkeys have the capacity necessary to remember both using short-term memory has been inconclusive. In HintRecall we provide list-items simultaneously and use hints to reveal the order of the list. Monkeys are required to press the item that is flashing, at which time the next item in the list begins to flash. Once they have gone through the list during the presentation phase of the trial they are then give a test. List items are displayed again without any hint to order. Subjects are required to press the items in the order given them during the presentation phase of the trial in order to receive reinforcement. The list varies from trial to trial so no long-term memory is required. This test requires short-term memory of both item and order information.
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Cognitive imitation was demonstrated in rhesus macaques that were trained on a serial task in which arbitrarily selected photographs had to be touched in a particular order. The position of the photographs varied randomly from trial-to-trial to prevent subjects from learning lists as particular motor sequences. List-naïve monkeys learned new lists more rapidly when they could observe an experienced monkey execute the list than when they had to learn lists in isolation, by trial-and-error. Control conditions ruled out social facilitation and computer feedback as explanations of that difference. This suggests a qualitative difference between the mechanisms underlying cognitive and motor imitation
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We concluded that the monkeys were effectively able to monitor their memory, as their risk-accuracy correlation was positive (and became stronger with each transfer to a new task). This correlation is a measure of how often they chose high risk following a correct response, and low risk following an incorrect one.