They concluded that their results were statistically significant.Īmong humans, researchers have found that general intelligence can account for about 40% of the individual differences in IQ-type test scores. To tease out whether these correlations were due to a small sample size or chance, the researchers used a more sophisticated statistical technique called principal components analysis, testing the actual results against 10,000 randomly generated simulations. For example, if a robin did better on the motor skills or the color discrimination test, it was more likely to do better on the spatial memory test as well. Their program found a weak but positive correlation between how well any particular bird did on one test and its performance on the other five tests. The researchers then turned to computers to analyze how the birds did overall. On the spatial memory test, the birds flipped the wrong lids between zero and 13 times in their attempts to find the worm 24 to 48 hours after they had seen where the experimenter put it. For example, the birds required between 10 and 18 trials to successfully complete the motor skills test, between 12 and 80 trials to figure out the color discrimination challenge, and between 13 and 86 trials to get the symbol test right. In a paper published online this week in Animal Behaviour, Shaw and her colleagues report wide variations in how well the birds did on multiple trials of each test. This demonstrated that they were hungry enough to do their best on the exam. To be sure that the robins were motivated to cooperate in the experiment, the researchers trained the birds to hop onto a scale and eat a single worm both before and after each test. They saw how well the birds could remember in which of eight wells the researchers had hidden a worm. And because these robins store food for the winter, the scientists also measured their spatial memories. To show they could distinguish symbols, they had to discern whether the worm was under a lid marked with a cross or a square. In another-designed to test their ability to distinguish colors-the birds had to figure out whether the worm was hiding under a red or a blue lid. In a test of motor skills, for example, the birds learned to flip plastic lids covering wells in a wooden board, one of which had a tasty mealworm at the bottom. Shaw and her colleagues briefly captured and banded 20 adult birds, which they trained to carry out six different tests to measure various skills thought to be linked to specific types of animal cognition (defined as the ability to acquire, process, and act on information about the environment). The robins live at the Zealandia wildlife sanctuary, a 225-hectare nature paradise in Wellington where more than 700 of the birds live wild and protected from predators in the middle of the city. To get around some of these limitations, a team led by Rachael Shaw, an animal behavior researcher at Victoria University of Wellington, turned to a population of New Zealand North Island robins for a new round of experiments. Thus, even studies that suggest variations in intelligence among mice, birds, and apes all carry the caveat that alternative explanations could be at play. Because most experiments award would-be test-takers with food, an empty (or a full) stomach might be all it takes to skew the results. Second, differences in animal test scores can depend on how motivated they are to perform. When it comes to animals, the problem is compounded for two main reasons: First, it is very difficult to design and administer tests that pick up on overall smarts instead of specific skills, such as the keen memories of food-hoarding birds or the fine motor skills of chimpanzees that make tools for finding insects in trees. In humans, factors like education and socioeconomic status can affect performance. For years, researchers have questioned whether measurable differences exist in humans and nonhumans alike. General intelligence is usually defined as the ability to do well on multiple cognitive tasks, from math skills to problem solving. But a new study, in which scientists tested wild robins on a variety of skills, concludes that they do differ in the kind of "general intelligence" that IQ tests are supposed to measure. Are some animals smarter than others? It's hard to say, because you can't sit a chimpanzee or a mouse down at a table for an IQ test.
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