Investigations of mirror self-recognition (SR) in chimpanzees (Pan troglodytes) have had small samples and divergent methods. In Experiment 1, 105 chimpanzees (10 months to 40 years of age) were observed for signs of SR across 5 days of continuous mirror exposure. In Experiments 2 and 3, negative SR adult and adolescent chimpanzees were saturated with mirror exposure in efforts to facilitate SR and a longitudinal study was conducted with a number of young subjects. In Experiment 4, mark tests were administered to groups of positive SR, negative SR, and ambiguous SR subjects. In Experiment 5, we explored whether previous positive SR reports in young chimpanzees were artifacts of increased arousal during mirror exposure. Results suggest that SR typically emerges at 4.5-8 years of age, at the population level the capacity declines in adulthood, and in group settings SR typically occurs within minutes of a subject's exposure to a mirror.

The ability of young children to recognize themselves in delayed videotapes and recent photographs was investigated using a delayed analog of the mirror mark test, as well as verbal reports. In Experiment 1, 42 2-4-year-old children were videotaped while playing an unusual game. During the game an experimenter covertly placed a large sticker on the child's head. The videotape was played back 3 min later to the children. Older, but not younger, children reached up to remove the sticker when the tape revealed it being placed on their heads. In Experiment 2, a similar procedure was used with 60 3- and 4-year-olds where Polaroid photographs were taken during and after the act of the sticker being placed on the child's head. When allowed to look at the photographs, young 3-year-olds did not reach up to search for the sticker, whereas older 3- and 4-year-olds did. Almost all of the children who did not appear to realize that there was a sticker on their head from the information provided by the photographs did provide a correct verbal label for the image, and reached up to remove the sticker when presented with a mirror. Experiment 3 compared the reaction of 48 2 1/2-3 1/2-year-olds to live versus delayed video feedback and indicated an effect of the temporal aspect of the stimulus. The results are discussed in the context of the different forms of self-conception that may underwrite the 2 manifestations of self-recognition.

The ability of young children to recognize themselves in delayed videotapes and recent photographs was investigated using a delayed analog of the mirror mark test, as well as verbal reports. In Experiment 1, 42 2-4-year-old children were videotaped while playing an unusual game. During the game an experimenter covertly placed a large sticker on the child's head. The videotape was played back 3 min later to the children. Older, but not younger, children reached up to remove the sticker when the tape revealed it being placed on their heads. In Experiment 2, a similar procedure was used with 60 3- and 4-year-olds where Polaroid photographs were taken during and after the act of the sticker being placed on the child's head. When allowed to look at the photographs, young 3-year-olds did not reach up to search for the sticker, whereas older 3- and 4-year-olds did. Almost all of the children who did not appear to realize that there was a sticker on their head from the information provided by the photographs did provide a correct verbal label for the image, and reached up to remove the sticker when presented with a mirror. Experiment 3 compared the reaction of 48 2 1/2-3 1/2-year-olds to live versus delayed video feedback and indicated an effect of the temporal aspect of the stimulus. The results are discussed in the context of the different forms of self-conception that may underwrite the 2 manifestations of self-recognition.

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