How early and later-acquired experience affects the age bias in face recognition: an exploration of age-of-acquisition effects.

In this doctoral dissertation I present some of the studies conducted during my PhD aimed to investigate how face processing abilities develop across the lifespan and how the face representation system adapts to reflect each individual's social experience. As adults we are expert at processing faces; nevertheless our ability is greater for some categories of faces than for others, giving rise to recognition biases based on social dimensions such as species, race and age. These biases have been interpreted as a result of the interaction between individual motivation and perceptual experience provided by social environment, which work together in affecting the way we encode, process and mentally represent faces. The studies presented in this dissertation focused on the age bias that is the variability in face recognition abilities determined by the relation between the age of the observer and the age of the perceived face. Specifically I will discuss recent evidence suggesting the presence of a processing advantage for adult versus non-adult faces in the lifespan (from infancy to old age) and I will provide novel evidence on how the time of acquisition modulates the effects of individual experience with non –adult faces on this perceptual advantage for adult faces across the life-span. In Chapter 1 I will investigate the short- and long-term effects of early-acquired experience with a child or an infant face provided by the presence of a younger or older sibling in our participants’ family household. Study 1 and Study 2 investigated the behavioral and the neural correlates of the perceptual tuning towards adult faces and its modulation as a consequence of sibling experience, within the first year of life. These two studies show that early-acquired experience has a critical role in the emergence of neurocognitive specialization for adult faces. Study 3 provides evidence on the long-lasting effects of this early acquired experience in interaction with later-acquired experience during adulthood: recognition ability for adult and infant faces was tested in first-time mothers who were or were not exposed to sibling experience in their first years of life. Results show that experience acquired early in life has a greater impact than the one acquired later in life, as only mothers with a younger sibling were able to bootstrap perceptual learning of infant faces from exposure to their own child. These findings suggest that early-acquired experience has continuous effects into adulthood, as it preserves the system from the loss of plasticity that would otherwise take place. In Chapter 2 I will investigate the extent to which face representation system remains plastic during adulthood and old age. Results show that professional experience with older adult individuals in adulthood and social experience with peers in old age reduce the magnitude of the recognition advantage for adult faces suggesting that experience with multiple individuals is capable to modulate face processing abilities even in adulthood and old age. Lastly Study 6 investigated how face age affects the deployment of selective visual attention and whether this effect is modulated by professional experience with non-adult faces acquired later in development. Findings provided by this last work extend the few existing evidence on the impact of face dimensions, such as age and race, on visual attention and yielded novel insights into the differential mechanisms underlying the age and the race bias. Overall these studies confirmed the plasticity of the face representational system which constantly adapts to reflect the individual’s current social and perceptual experience across the whole lifespan from infancy up to old age.