The Mirror Test

Gallup (1977) is famous for arguing that animals, particularly the great apes (chimpanzees and gorillas) do indeed have human-like consciousness. In one famous series of experiments, he studied the ability of apes to recognize mirror images of themselves. He assumed that if they recognized their image in the mirror, they had some kind of self-awareness. . That can be debated, but at least it is an objective measure.

What was Gallup's experiment on self-recognition in apes?

First Gallup gave chimpanzees 10 days of exposure to full-length mirrors. During the 10 days, frequency of "other-directed behaviors" such as threat displays directed toward the mirror rapidly fell to near zero. Then he anesthetized the chimps and painted the top half of an eyebrow ridge with "bright red, odorless, non-irritating, alcohol-soluble dye." The marks were located so the animals could not see them without the mirror.

When the chimps awoke from the anesthesia, they were placed in front of the mirror. They increased their frequency of mirror-looking behavior by over 25 times. They touched the red spot, and they smelled and examined their fingers after touching the red area "even though the dye had long since dried and was indelible" (Gallup, 1977). Gallup and other investigators found that a variety of other primates, such as baboons, macaques, mandrills, and two species of gibbons did not respond this way. Gallup and his colleagues concluded that this ability was unique to humans and great apes.

A team of behaviorists, Epstein, Lanza, and Skinner (1981), could not leave this claim of "animal consciousness" unchallenged. What if a pigeon could be taught to do the same thing? Would we attribute self-consciousness to a bird? They decided to use conditioning techniques to see if they could teach pigeons to behave like Gallup's apes.

How did Epstein and Skinner respond to Gallup's experiment?

First the researchers taught pigeons to peck white flecks of paper off their own bodies, using a shaping procedure. Then they taught them to peck at things they could see only in a mirror. Finally they fitted the pigeons with collars so the birds could not see their own bodies except in a mirror. Then they put flecks of paper on their bodies where they could not see them, except in the mirror.

Sure enough, the pigeons reached around the collar and pecked off the flecks of paper that they could see only in the mirror. Evidently they referred the mirror image to their own bodies. The researchers triumphantly concluded that Gallup was wrong to use this task as an operational definition of self-awareness, because (obviously? transparently?) pigeons would not have self-consciousness of the sort Gallup was claiming for apes.

What is "one problem" with the Epstein and Skinner rebuttal to Gallup?

There is one problem with the Epstein, Lanza, & Skinner (1981) rebuttal to Gallup. The researchers seemed to be making the same assumption in their own work that they were criitcizing in the work of Gallup: that the "same" behavior in two different species represented the same subjective events. Pigeons could do the mirror task, and pigeons probably lack self-consciousness, ergo apes who could do the mirror task were not necessarily self-conscious. This logic only works if pigeons and apes go through the same cognitive processes in performing the task, and we do not know that.

What are some other criticisms of Gallup's research or conclusions?

Gallup's experiment has been criticized on various other grounds. Westergaard and Hopkins (1994) noted, "Only 20%...of the chimpanzees he actually tested actually passed the notorious mark test." They also pointed out that "effects of human contact on the development of self-recognition in chimpanzees and orangutans have yet to be assessed." In other words, this may not be a spontaneous or natural behavior. Finally, they point out that monkeys, too, readily learn to use mirrors to guide their own hand movements to obtain hidden food, so perhaps the discontinuity between monkey and apes (emphasized by Gallup) is not as great as first appears. Despite the criticisms, Gallup's research has definitely been successful in one way: raising questions, stimulating thought, and inspiring new research.

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Copyright © 2007 Russ Dewey