Chimps intelligent enough to appreciate a full pint

Last Updated: Wednesday, February 24, 2010 - 14:12

London: New research has shown that chimpanzees are intelligent enough to appreciate how big a pint of liquid is, or the volume of any other measure.

According to the report, the findings came from tests carried out by comparative psychologist Dr Michael Beran of Georgia State University, Atlanta, US, on three chimps, a 37-year-old female called Lana, a 21-year-old female called Panzee and a 34-year-old male called Sherman.

In the first experiment, Dr Beran poured quantities of fruit juice from a 600ml syringe into a clear cup and opaque cup. The chimps watched as he did so, and then choose the larger to drink.

It did not matter if Dr Beran poured 100ml, 200ml, 300ml or so on up to 600ml into either cup. More than three quarters of the time, the chimps would select the larger volume.

Crucially, by pouring the liquid into opaque containers, the chimps could only see how much was being poured, not how much had accumulated in the measuring cup. That means the chimps could accurately visualize or understand how much liquid was being poured, rather than collected.

“They had to watch juice pour into containers and once the juice was there, it was out of sight. So they had to remember how much juice is there, just from seeing it fall,” Dr Beran said.

In a second set of experiments, the chimps had to choose between a clear cup already containing a certain volume of juice, and another they couldn’t see, but into which was poured a drink.

That meant the chimps could not take the relatively easy option of timing the pouring events, and choose whichever cup had liquid poured into it for longer. “This is a complicated feat because there are no cues such as duration of pouring or height of the liquid that can be used,” explained Dr Beran.

“They must represent and compare the poured amount to the visible amount, and estimate which is larger,” he said. Again the chimps easily appreciated the difference. In a third set of experiments, Dr Beran then varied the height from which the liquids were poured.

That creates a perceptual illusion that might confuse the chimps. However, it made little difference to all three chimps, which picked the largest amount over 80 percent of the time, with Panzee scoring a high of 86 percent.

“The results support the position that chimpanzees are good mental accountants who judge various forms of quantities,” said Dr Beran.

ANI



First Published: Wednesday, February 24, 2010 - 14:12

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