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February 1995 Bird Brains Are No Hindrance To Time SenseWEST LAFAYETTE, Ind.–Time flies, but birds keep track. A Purdue University study shows that pigeons have a remarkable sense of time, and in some cases, are better than humans at determining intervals of time. "Though it has long been established that birds have a keen sense of time, our feathered friends are proving to be much more adept at judging time than we thought," says J. Gregor Fetterman, associate professor of psychology at Indiana University-Purdue University Indianapolis, who specializes in animal psychology. Fetterman's studies focus on relational learning–the ability to compare events in a relative way, as opposed to an absolute way–for instance, judging in terms of heavier, faster, longer, etc. He used pigeons for his study because they often have difficulty learning tasks that involve judgments about event relations. In his studies, however, the pigeons proved to be more adept than humans at some of these comparisons. Their keen sense of time was especially apparent when the birds were asked to determine whether specific intervals were in proportion to a set time interval. "Distinguishing whether two intervals of time are a three-to-one ratio or a two-to-one ratio can be difficult, and requires the ability to think in the abstract," Fetterman says. "This is the first study to show that birds may have the ability to relate one event to another." A sense of time is involved in all coordinated movements, both in humans and other animals, Fetterman says. "In birds, time sense helps determine several behaviors, such as when to forage for food, when to migrate, and how to sing." For example, a sense of time may help birds develop optimal foraging behavior, he says. "An optimal forager will keep track of how long it has been looking for food and how much food it has found. Time can serve as a cue about when to go somewhere else to look for food." Timing is also a critical component of singing for birds, which involves learning the sequence, pitch and duration of notes. Fetterman tested the pigeons' ability to determine intervals of time by showing them separate red and green lights, with each color light presented for a different amount of time. The pigeons were rewarded with food when they correctly indicated which light was on for a longer period of time by pecking a disc of matching color. The pigeons were accurate about 85 percent of the time–only slightly less often than a control set of human subjects. In another study, the pigeons were exposed to two intervals of red light followed by green, which were presented in a specific ratio, such as 3-to-1. For example, a light interval of 30 seconds was followed by an interval of light that lasted 10 seconds. In this way, the pigeons were trained to recognize lights presented in a specific ratio. To test the birds' ability to relate this learning to other events, Fetterman then varied the two intervals of lights, making the ratios greater than or less than 3-to- 1. For example, the first light may appear for 40 seconds, and the second for 10 seconds, resulting in a ratio greater than 3-to-1. The pigeons indicated whether the time intervals were greater or less than the original ratio by pecking different discs. Though half the tests used time intervals that were longer than 3-to- 1, and half used shorter time intervals, the length of time varied so that the birds could not simply memorize a particular set of intervals. Again, the pigeons were accurate approximately 85 percent of the time. The human subjects were correct only 70 percent of the time on the ratio test. Though humans generally have a better sense of time than pigeons, they are not used to judging time in ratios, Fetterman says. "For humans, language probably regulates our sense of time," he says. "In spoken language, we use relational terms like 'longer than' or 'shorter than' to describe our temporal experiences." He hopes to follow up these results with studies on monkeys and young children who have not yet developed strong language skills, to further analyze the role that language plays in judging time. Fetterman's studies were supported by the National Science Foundation. He has published his findings in the Journal of Experimental Psychology: Animal Behavior Processes, and in the Journal of Comparative Psychology. He presented his results at the Midwestern Psychological Association conference in May and at the International Society for Psychophysics in Vancouver in August. Purdue News Service: (765) 494-2096; purduenews@purdue.edu
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