The present study investigated whether prior consumption of garlic by nursing mothers modifies their infant's behaviors during breast-feeding when the mothers again consume garlic. Three groups of mother-infant dyads were studied. The groups differed in the type (placebo or garlic) or the timing (d 5-7 or 8-10) of capsule ingestion by the mothers and, consequently, in the amount and recency of exposure their infants had to garlic-flavored milk during an 11-d experimental period. Each mother-infant pair was observed during two 4-h test sessions. The first session occurred at the beginning of the experimental period, when the mothers ingested placebo capsules (d 4); the second occurred at the end of the experimental period, when they ingested garlic capsules (d 11). During test sessions, the infants fed on demand and were weighed before and after each breast-feeding to determine the amount of milk ingested, and their behaviors during breast-feeding were monitored by videotape. The results demonstrated an effect of prior experience with garlic in mother's milk. The infants who had no exposure to garlic volatiles in their mothers' milk during the experimental period spent significantly more time breast-feeding after their mothers ingested garlic capsules compared with those infants whose mothers repeatedly consumed garlic during the experimental period. Moreover, the former group of infants spent significantly more time attached to their mothers' breasts during the 4-h test session in which their mothers ingested the garlic compared with the session in which she ingested the placebo.(ABSTRACT TRUNCATED AT 250 WORDS)