Think of a little baby trying to understand the world. One thing they need to be able to deal with is causal relationships. They seem to come with their visual systems able to identify some simple events, for example the ‘launching effect’ where one moving object contacts another stationary one and imparts its motion to the stationary object. Identifying objects that seem to control other objects is an important starting point for understanding events. I had presumed this is why infants notice hands and follow their movements. Hands, including their own, are movers of other things. Well, I still do assume this importance of hands to infants, but a recent paper by Yu and Smith adds more importance to hands (see citation below). They are useful in establishing joint attention.
Joint attention is a key to communication. Once two people are both attending to the same object/event and know it, they can communicate. Even without language - through gesture, posture, facial expression and little noises - they can ‘discuss’ the joint target of their attention. With language, words become the pointers to steer joint attention, not just to objects in sight but to objects and metaphors in the mind. Being able to establish and maintain joint attention is very important for infants to master in order to go on to master a number of skills including language.
Until recently it was thought that infants established joint attention by following the eye movements of their partner. But this is quite a difficult skill. The eye movements are small, not too accurate and limited in availability. On the other hand, hand movements are very clear and accurate. Most people move their eyes in the same direction as they move their hands when they are using their hands. It is more efficient for an infant to follow hand movement then eye movements.
Here is part of the Yu/Smith paper:
One-year-olds and their parents temporally coordinated their visual attention to objects and did so smoothly, consistently, and as equal partners without one partner dominating or leading the interaction. Further, the two partners often shifted attention to the same objects together in time. (One way) to coordinated visual attention: each partner looks to the other’s eyes and the seen direction of gaze of the partner influences the direction of the other partner’s gaze, leading to coupled looking behavior. (An other way) alternate pathway: Within individuals a tight coordination of hand and eye in goal-directed action means that hand and eye actions present spatially redundant signals but with the hand cue being more spatially precise and temporally stable. The results show that the hand actions of an actor have a direct effect on the partner’s looking, leading to coordinated visual attention without direct gaze following. This hand-eye pathway is used by one-year-olds and their parents, and supports a dynamic coordination of the partners’ fixations that is characterized by rapid socially coordinated adjustments of looking behavior. The documentation of a functional alternative to following the eye gaze of a social partner begins to fill the contemporary knowledge gap in understanding just how joint attention between infants and parents might work in cluttered and complex everyday contexts. Joint attention as a means of establishing common reference is essential to infant learning in many domains including language and the present results show how coordinated looking may be established and maintained in spatially and dynamically complex contexts that include manual actions on objects. Infant attention and sensitivity to hand actions demonstrated in the present results is also consistent with the large and growing literature on their ability to interpret the causal implications of hand movements and gestures .
Successful adult social interactions are known to depend on rapid (with fractions of a second) behavioral adjustments in response to and across a suite of sensory-motor behaviors that include eye, head, hand, mouth, and posture movements. The hand-eye pathway evident in one-year-olds and their parents shows this same character of well-coordinated rapid adjustment in response to the partner.
Yu C, & Smith LB (2013). Joint Attention without Gaze Following: Human Infants and Their Parents Coordinate Visual Attention to Objects through Eye-Hand Coordination. PloS one, 8 (11) PMID: 24236151