She pulls out another plastic cage, occupied by a large white rat with red eyes that is nursing a dozen 21 - day - old pups. (scientificamerican.com)
In the early part of the twentieth century, the behaviorists Watson and Rayner, in an attempt to prove that fear was a learned behavior, exposed nine - month - old «Little Albert» to neutral stimuli like white rats, monkeys, and sheaves of burned newsprint. (bookbrowse.com)
«My father used to train large white rats for the circus,» Max says. (si.com)