Martin Schein, founder of the Animal Behavior Society in 1964, studied the diet of brown rats and came to the conclusion that the most-liked foods of brown rats include scrambled eggs, macaroni and cheese, raw carrots, and cooked corn kernels.
According to Schein, the least-liked foods were raw beets, peaches, and raw celery.
The vocalization, described as a distinct "chirping", has been likened to laughter, and is interpreted as an expectation of something rewarding.
Like most rat vocalizations, the chirping is too high in pitch for humans to hear without special equipment.
Selective breeding of Rattus norvegicus has produced the laboratory rat, a model organism in biological research, as well as pet rats. However, the English naturalist John Berkenhout, author of the 1769 book Outlines of the Natural History of Great Britain, is most likely responsible for popularizing the misnomer.