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Olfactory (odor recognition) information is important in the interaction between parents and their infants. Each can recognize the other's odor, and infants can recognize and remember odors soon after birth. Studies have shown that humans can be trained to associate a particular odor with a second stimulus such as a pleasant touch. This type of classical conditioning relies on normal function in two brain areas. If newborns were found to be responsive to this type of conditioning, then function of the involved brain areas could be tested soon after birth. The ability of 66 one-day-old infants to respond to olfactory conditioning was evaluated. In the study, responses to a citrus odor were evaluated when the odor was presented a second time, after an initial presentation was immediately followed by gentle stroking. Responses to this situation were compared with those in which stroking initially preceded the odor or when the odor or stroking was given alone. Only infants who were given the odor and then stroking responded to the second presentation of the odor, by turning the head toward the odor. Responses were apparently odor-specific, as infants did not respond to a novel floral odor. Neither sex, method of obstetrical delivery, nor method of feeding influenced which infants responded. Both sleeping and awake infants responded. None of the infants given stroking followed by the odor, or odor or stroking alone, showed this response. The results indicate that infants are capable of complex learning within the first 48 hours of life, and this may allow early screening of newborns for brain damage. (Consumer Summary produced by Reliance Medical Information, Inc.)