Biomedical subjects
Publications and source records attributed to Julien Gross.
Six- and 9-month-old human infants were tested in a deferred imitation paradigm in which an experimenter performed a single action with a novel object. Although infants of both ages imitated the action when tested immediately, only the 9-month-olds exhibited imitation after a 24-h delay.
Two alternative hypotheses have been generated to account for seasonal variation in the birth weight of human infants born in industrialized countries. First, it has been hypothesized that low ambient temperature during the second trimester of gestation decreases birth weight. Second, it has been hypothesized that exposure to bright sunshine during the first trimester increases birth weight. We tested these two hypotheses to determine which, if either, accounted for seasonal variation in birth weight of full-term infants. Birth weight data, collected over a 5-year period, were analyzed as a function of peak and trough sunshine and ambient temperature. Although there was no effect of ambient temperature during any trimester on birth weight, infants whose mothers were exposed to peak sunshine during their first trimester were born significantly heavier than infants whose mothers experienced trough levels of sunshine during the same trimester. Furthermore, infants whose mothers were exposed to trough levels of sunshine during their second and third trimesters were born significantly heavier than infants whose mothers were exposed to peak levels of sunshine during the same trimesters. We hypothesize that high levels of sunshine during early gestation may increase the level of insulin-like growth factor (IGF)-1, facilitating prenatal growth.
Although the mobile conjugate reinforcement, deferred imitation, and visual attention paradigms are commonly used to test memory processing by infants, there is often debate about the comparability of memory measured by these three procedures. In a series of experiments, we systematically compared 6-month-old infants' performance across all three procedures. Contrary to current claims, measures of memory obtained using the mobile conjugate reinforcement and deferred imitation paradigms were more similar than those obtained using the deferred imitation and visual attention paradigms.