Pressure variations applied by newborns and by infants 1 to 4 months old to rubber nipples were recorded in three different procedures under no-fluid conditions. In the first study, infants were presented for 90 seconds with novel nipples varying in shape and in shape plus material. Results suggested that a developmental trend existed for an increase in oral exploration and decrease in sucking. Further, this age trend was found to be influenced by the type of nipple. In the second study, infants were successively presented with novel rubber nipples for 10 time blocks 30 seconds long and separated by pauses 30 seconds in duration. Results showed that, according to age, repeated presentations caused different variabilities of the mean proportion of two patterns of response: sucking and exploration. Finally, in a third investigation, gustative parameters as opposed to "geometric" features of the intra-oral stimulus were manipulated. Infants were presented for 30 seconds with a dry nipple, one previously soaked in water, or one soaked in water with 15 percent sucrose. Results confirmed the general evolution of exploration and sucking patterns of response, with responses not being significantly affected by the introduced gustative variations. Results were interpreted to support the contention that there is a double function of the mouth: nutritive as well as perceptual, with the latter function gaining in importance within the first months of life. (Author/RH)