observed without a mirror, picking their noses, making faces, and blowing bubbles at their own reflections. Gallup expanded the study by manipulating the chimpanzees' appearance and observing their reaction to their reflection in the mirror. Gallup anesthetized the chimps and then painted a red alcohol-soluble dye on the eyebrow ridge and on the top half of the opposite ear. When the dye dried, it had virtually no olfactory or tactile cues. Gallup then removed the mirror before returning the chimpanzees to the cage. After regaining full consciousness, he then recorded the frequency with which the chimps spontaneously touched the marked areas of skin. After 30 minutes, the mirror was reintroduced into the cage and the frequency of touching the marked areas again determined. The frequency increased four to ten, with the mirror present, compared to only one when the mirror had been removed. The chimpanzees sometimes visually or olfactorily inspected their fingers after touching the marks. Other mark-directed behavior included turning and adjusting of the body to better view the mark in the mirror, or tactile examination of the mark with an appendage while viewing the mirror. An important aspect of the classical mark-test (or rouge test) is that the mark/dye is nontactile, preventing attention being drawn to the marking through additional perceptual cues (somesthesis). For this reason, animals in the majority of classical tests are anesthetized. Some tests use a tactile marker. If the creature stares unusually long at the part of its body with the mark or tries to rub it off, then it is said to pass the test. Animals that are considered to be able to recognize themselves in a mirror typically progress through four stages of behavior when facing a mirror: Gallup conducted a follow-up study in which two chimps with no prior experience of a mirror were put under anesthesia, marked, and observed. After recovery, they made no mark-directed behaviors either before or after being provided with a mirror. The rouge test was also done by Michael Lewis and Jeanne Brooks-Gunn in 1979 for the purpose of self-recognition with human mothers and their children. Implication and alternate explanations The default implication drawn from Gallup's test is that those animals who pass the test possess some form of self-recognition. However, a number of authors have suggested alternative explanations of a pass. For example, Povinelli suggests that the animal may see the reflection as some odd