Both infantile stimulation and exposure to sweet food lead to an increased sweet food ingestion in adult life.

The timing of early experience changes when a food preference appears

An effect of early experience may be present biologically before it becomes visible in behavior. This study examined when increased sweet-food intake emerged after neonatal handling and whether later experiences could produce a similar adult pattern.

Comparing experiences at different ages. Male rats were handled briefly during the first ten days after birth or left undisturbed. Some then encountered sweet food and were tested before puberty as well as in adulthood; others first encountered the food during adult testing. In a separate experiment, previously unhandled animals explored an environment containing toys around the preadolescent period before their adult food intake was assessed.

Several early experiences converged on later intake. The increased sweet-food consumption associated with neonatal handling appeared when habituation and testing occurred after puberty. It was not seen in the same way before puberty. Early exposure to the sweet food itself also mattered: control animals exposed between days twenty-two and twenty-seven ate more of it as adults. Exposure to the environment containing toys produced a similar increase in adult sweet-food intake.

These findings show that an adult feeding pattern can arise after more than one kind of early experience, and that the age of both exposure and testing changes what is observed. They also identify a methodological issue: familiarizing young animals with a food for an early test can itself alter the behavior measured later.

The study does not show that all stimulation has the same effect or that greater sweet-food intake necessarily indicates poorer health. It demonstrates developmental plasticity, the capacity for experience to produce lasting changes, and suggests that maturation influences how those changes are expressed. The biological mechanism linking these different experiences to adult intake remained to be established.