Infants raised with pets learn to mentally sort animals into categories effectively at younger ages than those raised without pets, according to a study published in the Journal of Cognitive Development.

Previous research has shown that human infants have are able to recognize dogs and cats, and can tell the difference between them, at very young ages. A key part of recognizing something is knowing what part to look at to distinguish it from other kinds of things. In the case of domestic animals, the head is the distinguishing feature both for categorization and for understanding their behavior. Just as infants instinctively look at key features of human faces, like the eyes and mouth, children as young as three months old appear to focus their attention on the heads of cats and dogs.

Two researchers from the University of California, Davis, Karinna Hurley and Lisa Oakes, conducted a study to determine whether this early affinity for domestic animals depended on infants’ early experience with pets. The study included 48 healthy 4-month old infants. Twenty-seven of the infants either lived in homes with cats or dogs, or spent at least 10 hours a day in a daycare setting with these pets.

The remaining 21 infants had no exposure to domestic animals. Both groups were shown a series of images of pets, as well as two types of control image (human faces and vehicles). The researchers were interested in seeing how much attention the infants paid to the pets’ heads in comparison to the rest of their bodies. The movements of the infants’ eyes were monitored and recorded while they watched each image for three seconds.

Babies who lived with pets were more focused on the heads of the cats and dogs than those who had not been exposed to pets, indicating that they recognized the domestic animals and that they were processing the information in the images more effectively. The two groups of infants did not differ in terms of how they focused on images of human faces or vehicles, indicating that these differences in processing were specific to the category of domestic animals.

The study authors conclude that learning from experience is an important part of infant cognitive development. Those exposed to pets had already, at four months of age, developed a mental model of dogs and cats that allowed them both to recognize members of this category and focus their attention on the part of the animal most related to action. These results suggest that active cognitive engagement and learning begin even at the earliest of ages.