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We report a longitudinal study investigating developmental changes in the structure of attention engagement during early infancy. Forty-three infants were observed monthly from 2 to 4 months. Attention engagement was assessed from play interactions with parents, using a coding system developed by Bakeman and Adamson (1984). The results indicated a developmental transition in attention engagement at 3 months: after this age infants engaged for longer periods and in a wider variety of states. Most infants displayed person engagement at 2 months, passive joint engagement at 3 months, and object engagement at 4 months. To address whether emerging abilities of attention engagement allow infants to follow the attention of social partners, we compared attention engagement to performance on an experimental measure of attention control (reported by Perra & Gattis, 2010). Analyses revealed a positive relation between passive joint engagement and checking back, suggesting that changes in passive joint engagement reflect the development in attention control., (Copyright © 2012 Elsevier Inc. All rights reserved.)

The control of social attention during early infancy was investigated in two studies. In both studies, an adult turned towards one of two targets within the infant's immediate visual field. We tested: (a) whether infants were able to follow the direction of the adult's head turn; and (b) whether following a head turn was accompanied by further gaze shifts between experimenter and target. In the first study, 1-month-olds did not demonstrate attention following at the group level. In addition, those infants who turned towards the same target remained fixed on it and did not shift attention again. In Study 2, we tested infants longitudinally at 2-4 months. At the group level, infants followed the adult's head turn at 3 and 4 months but not at 2 months. Those infants who turned towards the same target at 3 and 4 months also shifted gaze back and forth between experimenter and target. By 3 months, infants seem able to capitalize on the social environment to disengage and distribute attention more flexibly. The results support the claim that the control of social attention begins in early infancy, and are consistent with the hypothesis that following the attention of other people is dependent on the development of disengagement skills.

Although much is now known about eye movement detection, little is known about the higher cognitive processes involved in joint attention. We developed video stimuli which when watched, engender an experience of joint attention in the observer. This allowed us to compare an experience of joint attention to nonjoint attention within an fMRI scanning environment. Joint attention was associated with activity in the ventromedial frontal cortex, the left superior frontal gyrus (BA10), cingulate cortex, and caudate nuclei. The ventromedial frontal cortex has been consistently shown to be activated during mental state attribution tasks. BA10 may serve a cognitive integration function, which in this case seems to utilize a perception-action matching process. The activation we identified in BA10 overlaps with a location of increased grey matter density that we recently found to be associated with autistic spectrum disorder. This study therefore constitutes evidence that the neural substrate of joint attention also serves a mentalizing function. The developmental failure of this substrate in the left anterior frontal lobe may be important in the etiology of autistic spectrum disorder.