Parental recognition in the rat

Infant rats were tested in a 2-choice test for their preference for (a) their mother vs an alien mother, (b) their father vs an alien father and (c) their father, whom they had never experienced, vs an alien father. Pups were able to recognize their mother and showed a preference for her for the duration of the experiment. Pups could also recognize their father, even if they had never previously experienced him. However, they showed a reversal in preference for their father during the experiment, preferring their father at Days 10-14, but preferring an alien father at Days 18-22. It is concluded that fathers are recognized by general cues of kinship through “phenotype matching”, whereas mothers assume a positive reinforcing value and are recognized by individual cues.