Friday 21 November 2014

Chimp digit span

At the same conference in Cambridge in July 1970 where I had lectured Arthur Jensen on the cultural explanation for black/white intelligence differences on Block Design and Object Assembly (he suggested these differences were unlikely to be cultural, and I argue that they were due to a lack of constructional toys in West Indian homes) I was also exposed to a stellar constellation of researchers, among whom David Premack made the most impact. He had been working with a clever chimpanzee called Sarah who had taught language-like manipulation of symbolic objects. Sarah’s skills astounded us, and we searched for artefacts in the experimental design to account for her uncommon abilities. Those of cynical disposition muttered “It must be Helen Keller in a fur coat”. Someone of greater breadth of intellect asked him what his ultimate purpose was in teaching a monkey to handle language. Premack replied: “So as to teach her how to pray”. I and others thought it an ironic put down, but those who quizzed him later came back astounded. “He was serious. He is a Skinnerian mystic”.


His Premack principle (1959) stuck with me, though I could never get child psychologists to implement it (reward a subject’s low frequency behaviour by letting the subject carry out a high frequency behaviour). Anyway, Premack triggered lots of very interesting work, based on the belief that our monkey cousins were brighter than they were given credit for. In 1978 he also proposed the Theory of Mind, with associated tests. Clever cookie. Respect.

Marty Seligman was at a previous conference where David Premack first presented his results on chimp language logic, and told me this story, gratified he had been present to witness this moment in the history of psychology. As Premack gave his lecture, and showed again and again the proofs that Sarah was capable of understanding language-like conditional probability in the manipulation of object symbols, the behavioural cynics tore in to him for a long time, trying to show he must be wrong. Finally, one hand was raised, and up stood  Keith Hayes who with Catherine Hayes had home schooled the young chimp Viki with their own child, and tried to get it to talk (for which task chimps do not have the appropriate vocal apparatus), all these heroic labours ending in abject failure with a mere 4 words mouthed.   Facing Premack for the first remark, and then turning to the audience to deliver the second, he said: “Looking back at all the work I did, I realize how stupid I was to try to get a monkey to talk. However, listening to the last half hour of criticisms, I am relieved to find I am not the stupidest person in the room”.

Here is a film that Roberto Colom sent me. When given to humans this particular physical digit-span like task is called Spatial Span on the Wechsler and I am reliably told that it is very difficult to do, and even more difficult for a clinical psychologist to administer, because you have to concentrate hard to make sure you have demonstrated each sequence correctly, and then have to concentrate even harder when the client quickly taps their repetition of the sequence (doing it fast before their memories fade, thus burdening the memory of the psychometrician trying to write down the results).

In the spirit of public education, I consented to be tested. First, you should note that at 10.45 pm, when my usual bedtime is 11 pm, I was not at my most alert. Second, I had been listening to the recordings of a mellifluous tenor who, aria by aria, was having a lowering and somnolent effect on my mood. Third, it is not considered good practice to be tested by one’s spouse.

5 forwards and 5 backwards, a scaled subtest score of 12. Long explanation follows: culturally biased test, stereotype threat, long term effects of being brought up in a cultural backwater in South America,  insufficient practice items, too late at night, lousy technique on my part which lacked any “chunking” strategies, marital competitiveness, and conflicting emotional undercurrents caused by doing the test in the kitchen, the scene of so many happy, nourishing family meals.

What a difficult test! No wonder Wechsler dropped it. See what a chimp makes of it.

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