The use of an adult as a resource for help and instruction in a problem solving situation was examined in 9, 14, and 18-month-old infants. Infants were placed in various situations ranging from a simple means-end task where a toy was placed beyond infants' prehensile space on a mat, to instances where an attractive toy was placed inside closed transparent boxes that were more or less difficult for the child to open. The experimenter gave hints and modelled the solution each time the infant made a request (pointing, reaching, or showing a box to the experimenter), or if the infant was unable to solve the problem. Infants' success on the problems, sensitivity to the experimenter's modelling, and communicative gestures (requests, co-occurrence of looking behaviour and requests) were analysed. Results show that older infants had better success in solving problems although they exhibited difficulties in solving the simple means-end task compared to the younger infants. Moreover, 14- and 18-month-olds were sensitive to the experimenter's modelling and used her demonstration cues to solve problems. By contrast, 9-month-olds did not show such sensitivity. Finally, 9-month-old infants displayed significantly fewer communicative gestures toward the adult compared to the other age groups, although in general, all infants tended to increase their frequency of requests as a function of problem difficulty. These observations support the idea that during the first half of the second year infants develop a new collaborative stance toward others. The stance is interpreted as foundational to teaching and instruction, two mechanisms of social learning that are sometime considered as specifically human. (Contains 4 tables, 3 figures and 4 notes.)