Researchers at the Institute for Primate Studies at the University of
Oklahoma taught ten signs of the American Sign Language to four
chimpanzees.  The signs were for listen, drink, shoe, key, more, food,
fruit, hat, look, and string. The study's goals were to determine
whether there was any consistency across signs in the ease with which signs were
learned and also whether there are chimp to chimp differences.

There were two young male chimps (Bruno and Booee) and two young
female chimps (Cindy and Thelma). The chimps were taught individually
(independently) using a reward system until each chimp could successfully
produce unprompted responses on five consecutive occasions.  The data are
the time (minutes) required to teach each sign to each subject.  The chimps
are numbered 1 (Booee), 2 (Cindy), 3 (Bruno), and 4 (Thelma) and the signs
are numbered in the order listed above.

The data originally appeared in the article:

R.S. Fouts (1973). "Acquisition and testing of gestural signs in four 
young chimpanzees," Science, 180:978-980.

and this description appeared in the book:

Ramsey and Schafer (1997). The Statistical Sleuth: A course in methods 
of data analysis, Duxbury Press.