Toddlers' pointing when joint attention is obstructed

Abstract
The aim of this study was to examine toddlers' ability to take their social partner's line of sight into account when engaging in joint attention. If pointing involves an understanding of the relationship between seeing and knowing, then specific modifications in communication should appear when joint attention is obstructed. In this study, obstacles were introduced in order to manipulate object visibility for the toddler's social partner. Thirty-two toddlers aged 18-23, 24-29, and 30-36 months were tested with an adult social partner and two animated clown mannequins. In Task 1, whereas both clowns were always visible to toddlers, there were three conditions varying the number of targets visible to the adult social partner (both, one, or none). In Task 2 toddler and social partner were sitting face-to-face, each having a clown fully visible (in front) and one not visible (behind). When attempting to communicate about an object not visible to the social partner, toddlers show increased levels of the following behaviours: pointing frequency; proportion of pointing accompanied by visual checking with the adult; anticipatory visual checking (just before pointing initiation); frequency of vocalizations associated with pointing; and frequency of language both associated with