ivory towers William Hartston

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Despite the attention given tolast week's imprisonment and subsequent release of Mrs Jean Knowlson, (aka the Birdwoman of Holloway), there has been little comment on how the pigeons of Purley felt about it all.

There has been a great deal of research on pigeons' homing abilities and a splendid paper by D Porter and A Neuringer ("Music discrimination by pigeons"; Journal of Experimental Psychology, 1984) which showed that pigeons can learn to discriminate between flute music by Bach and viola music by Hindemith with 80 per cent accuracy. But what about little old ladies with bin-liners full of bread?

A recent paper by HS Terrace, S Chen and AB Newman, "Serial Learning With a Wild Card by Pigeons (Columba livia): Effect of List Length" (Journal of Comparative Psychology, 1995, Vol 109, No 2) supports the argument that if Mrs Knowlson had kept the bread in five differently coloured bin- liners, and taught birds to eat from them in a specified order, then she might even have received a research grant. The paper shows that given five stimuli in a specified order, a pigeon is capable of learning to discriminate that order from others.

The researchers used differently coloured lights projected onto screens, with the pigeon rewarded with a food pellet if it pushed a lever after the lights were shone in the correct order.

The most interesting results came when pigeons were tested to see if they could correctly pick out subsets of the original order. For example, if the lights are shone in order A-B-C-D-E, can a pigeon learn that A- C or B-E are in the right order, while C-B or D-A are not?

If the pigeons are associating the stimuli with an ordinal list, they ought to be able to do it. The results show, however, that they can happily peck out any pair with A or E in it, but they cannot seem to get the hang of pairs from the middle of the list such as B-C or B-D. They are also very good at coping with the distraction of a substitute colour, or "wild card", W when it is introduced into the list at front or back as W-B- C-D-E or A-B-C-D-W, but they get confused if it is flung into the middle, A-B-W-D-E.

While pigeons can learn to perform as well as monkeys on the straight A-B-C-D-E tests, their performance is much worse on the subsets, or the wild card tests. Overall, the results suggest that a pigeon's ability to learn the middle of a list depends on the anchors of a beginning and an end.

Pigeons and monkeys clearly do not remember lists in the same way.