It's a Math World for Animals（4）

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    Likewise, 12-month-old babies look longer at a bigger pile of sugar cookies. Even though they can't talk or count, the babies seem to know how to go for more.

   Most interesting of all, says cognitive scientist Claudia Uller, is that those skills fall apart at about the same number in both monkeys and babies.

    "It's so incredible," says Uller, who is at the University of Louisiana at Lafayette . "It breaks down at around four. If you give babies two or three, they'll go for three. At three versus four, their choices are random. At four versus six, they're random." The same is true for monkeys and tamarins.

    Because primates and people are so closely related, Uller wanted to try the same experiment with a completely different kind of animal: salamanders. Amazingly, she found the same results.

    When shown test tubes holding different numbers of live fruit flies, redbacked salamanders looked at the tube that held more. But only up to a certain point. Just as in babies and monkeys, the system seemed to break down around four. Uller published her results recently in the journal Animal Cognition.