Do babies learn to perceive human faces

One of the most powerful and influential instruments in non-verbal communication is the human face. The human face conveys not only emotion but also facts about the human itself; from ethnicity and physical health to age and gender. It is perhaps the most easily recognisable and distinguishing feature of the human body.

Humans use facial expressions constantly during social interaction as a universal form of non-verbal communication, commonly recognised across all cultures. Without this, there would be a distinct barrier to cross-cultural interaction.Facial perception and processing therefore has a largely important bearing on non-verbal communication, which is perhaps why ‘newborn infants prefer to look at human faces over almost any other form of stimuli’ (Pascalis & Kelly, 2009). This preferential attention could be due to the dynamic movements of the human face and the sounds emitted from speech creating an interesting stimulus for an infant, or the face could be a ‘target’ stimulus that the infant is pre-programmed to devote attention to.There is a longstanding psychological debate concerning how infants perceive human faces.

A great proportion of modern psychological evidence suggests that babies do not learn to perceive human faces and that this perception is innate from birth; that infants are born with a pre-programmed ability to perceive, recognise and attend to human facial features (Morton & Johnson, 1991). Other evidence suggests that infants have some form of innate perceptual ability, but are not born with all perceptual skills and instead learn more complex perceptual tasks as they mature, such as learning to recognise the sex of a face (Leinbach & Fagot, 1993).One particular biological explanation for innate learning of the human face is the theory of Gestational Proprioceptive Feedback (GPF), (Quinn & Slater, 2003). Gestational Proprioceptive Feedback is an innate facial processing theory that came from evolutionary adaptation of the human species. It suggests that face perception is formed in utero before the infant is even born; facial movements made by the unborn infant could create a very early representation of a face that the infant knows by birth.

For this to happen, the unborn infant has to either be able to perform motor movements of limbs to be able to raise its arms to touch its own face, or be able to perform muscular facial movements such as blinking or opening its mouth in order to gain a perceptual representation of a human face.‘Cross-modal recognition’ is the final element in GPF which would enable this innate facial representation; the ability to match schematic facial stimuli presented visually with the utero-presentation that the infant is born with. Although hard to grasp, three day-old infants have been found to demonstrate cross-modal recognition for shapes (Steri & Gentaz, 2003).Morton and Johnson (1991) proposed a system-based theoretical explanation for infant perception of human faces using the terms ‘CONSPEC’ and ‘CONLERN’.

‘CONSPEC’ is the first of two innate systems that the infant uses, as this system is active immediately once the infant is born. As a subcortical visuomotor system, ‘CONSPEC’ encourages the infant to attend to patterns in their environment which appear to be like human faces. Increased visual attention to human faces maximises the infant’s ability to perceive and recognise them from its birth.The second system, ‘CONLERN’, usually becomes active around the two-month mark of the infant’s life and develops cortically as a result of frequent exposure to human faces. ‘CONLERN’ would therefore not become active without the innate process of ‘CONSPEC’, as it is the subcortical visuomotor system which ensures the infant’s exposure to faces from birth.

‘CONLERN’ is responsible for the specific learning of the visual characteristics of faces; a more advanced learning which would enable recognition.Support of ‘CONSPEC’ and ‘CONLERN’ comes from earlier experiments in which newborns showed preferential tracking of schematic faces as opposed to scrambled faces (Goren, Sarty, & Wu, (1975); Johnson, Dziurawiec, Ellis, & Morton, 1991), which implies the innate perceptual knowledge of the human face that ‘CONSPEC’ would provide the infant with from birth. The experiments involved an infant being presented with three differing stimuli: a schematic face-like image, a scrambled face-like image and a blank image as a control. Eye and head movements were greater in both experiments for schematic face-like stimuli, with further tracking demonstrating a specific interest in the schematic stimuli in comparison with the scrambled and blank stimuli.CONSPEC as a subcortical system is also supported in a finding that the facial preferences were only made when the face-like stimuli were presented in the temporal visual field, which translates information to subcortical pathways; no preference was elicited when stimuli were presented in the nasal visual field (Simion, Valenza, Umiltà, & Della Barba, 1995).However, ‘CONSPEC’ and ‘CONLERN’ theory (Morton & Johnson, 1991) cannot account for the vast amount of perceptual abilities found evident in newborns, such as preferences for attractiveness, sex and for a parent over a stranger.

Bushnell, Sai and Mullen (1989) experimented on forty four-day-old infants using live faces of a mother and a stranger matched for hair colour and facial brightness in pairs. The experiment resulted in the finding that infants had a strong and clear preference for their mother’s faces over the matched stranger. To ensure that the mothers had not cued their infants in some way, twenty naïve observers viewed each matched pair to ensure that the mother was not distinguishable from the stranger. None of the observers could determine which of the pair the infant’s mother was. This finding supports the idea that infants are born with an innate ability to perceive faces.Leinbach and Fagot (1993) examined the ability of eighty infants to perceive and categorise faces on the basis of sex.

The infants were either five, seven, nine or twelve months old during the experiment and were presented with twelve different same-sex faces as habituation stimuli. Two more faces, one male and one female, were utilised as test stimuli.Only the nine and twelve month-old infants showed a categorised distinction between the male and female faces, which suggests that some forms of facial perception (such as that of the sex of a human) are not entirely innate but can be developed with frequent exposure to face-like stimuli and therefore with learning. A small proportion of infants at younger ages (five and seven months) were also beginning to show categorisation, which demonstrates the learning element in this perception, as categorisation was fully possible for infants between nine and twelve months old.A second experiment involved altering hair length and including unisex clothing so that the male and female faces appeared to be the same for those cues.

Although categorical responses declined, there was still a significant amount of categorisation made by the older infants. It was found that by twelve months old, infants had clear categorisations for male and female faces, which may include hair length and clothing that was sex-typical.The findings from Leinbach and Fagot (1993) give evidence for an element of learning in their experiment, demonstrating the increase in sex-categorisation ability in infants as they mature. This particular area of face perception stands out from the other areas explored so far as it does not seem to be effective from birth, therefore may not be entirely innate or perhaps innate at all.

Infant perception of attractiveness, however, appears to begin much earlier than sex-categorisation. An experiment by Slater et al. (1998) found that infants as young as 14-151 hours from birth devoted longer attention (looking) on attractive faces than unattractive faces when paired together.A later experiment by Slater, Quinn, Hayes, and Brown (2000) found that two-day-old infants still had a preference for attractive faces over unattractive, yet also had a preference for upright faces as opposed to inverted faces. This suggests that infants’ early perception of faces as attractive is ‘orientation-specific’ (Slater, Quinn, Hayes & Brown, 2000), and that this upright-orientation perception of faces is either innate or rapidly learnt from birth.

Slater, Bremner, Johnson, Sherwood, Hayes and Brown (2000) conducted a study on ‘newborn infants’ preferences for attractive faces’ with focus on the role of external and internal facial features. The finding that infants as young as two days old make preferences on attractiveness by taking into account both internal and external facial features raised serious questions about the ‘Externality Effect’ (Bushnell, 1978). The ‘Externality Effect’ suggests that infants under two months of age cannot perceive the internal elements of geometric objects or faces and instead perceive a face only by its contours, until over 2 months of age when they have developed and learnt to perceive both external and internal features of a human face.It has since been suggested that infants consider both internal and external features of a human face as they perceive the stimuli, whether the face is static or dynamic.Vinter (1986) studied imitation and whether newborns can imitate both static and dynamic models.

Thirty-six infants of two to five days old were assigned randomly to three levels of the design: ‘static’ (tongue protrusion or hand open for twenty-five seconds and then closed), ‘movement’ (adult modelled a tongue protrusion and hand opening/closing) and control (the experimenter did not make any facial expressions and simply faced the infants).Highest rates of imitation were found in infants that had been exposed to the kinetic modelling of tongue protrusion or hand opening and closing, whilst infants exposed to static modelling failed to imitate the experimenter’s actions.The results show that kinetic actions play an important role in infant facial perception via imitation. Imitation is another example of an infant learning to perceive faces rapidly from birth; the infants have learnt to perform facial expression through kinetic modelling of expression from the experimenter.

Another argument for the development of face perception in later infancy through elements of learning ‘Perceptual Narrowing’ theory by Nelson (2001). This theory, when applied to face processing, suggests that infants may be born with some innate predisposition to processing faces in general. However, this innate predisposition develops through the repeated exposure of the infant to human faces in its first few months of life, to ‘tune’ the infant to focus on the human face by three months old. The infant is born with an ‘unspecified’ ability to recognise any face; including mammals such as monkeys (Pascalis, de Haan & Nelson, 2002).Pascalis, de Haan and Nelson (2002) examined how far six and nine month old infants were able to recognise human faces in comparison to the faces of another species; Rhesus Macaque monkeys.

At both ages the infants were able to demonstrate recognition of human faces, yet only six-month-old infants were able to demonstrate recognition for money faces. This suggests that infants become ‘tuned’ to specifically perceive human faces in the time span between six and nine months old, providing evidence for infants learning to perceive human faces.From the evidence provided and explored in this essay, it is arguable that babies do learn to perceive human faces, but this learning is only due to an innate predisposition to human facial representation.It is clear from evidence that some elements of facial perception (such as categorisation of sex and recognition of the face itself as human) come with learning and repeated exposure to the human face as the infant develops.

Learning of human face perception seems to be rapid, even considering the aforementioned learnt-perceptions. All perceptual abilities explored in this essay appear to be learnt by twelve months of age and most are learnt by as young as three months old.Perception of facial attractiveness was particularly strong evidence for the rapidity in which infants can learn to distinguish appealing faces from unappealing ones, whilst accounting for both orientation of the face and its internal features.Findings for infants perceiving internal facial features at an age as young as two days leaves an opening for wider research into the ‘Externality Effect’ (Bushnell, 1978) and research into how far this still applies, if it does still apply.

The ever-mounting modern evidence for innate face-perception abilities in infants has overwhelmed the weighting of the essay and therefore the conclusion must be that infants are born with an innate ability to perceive faces from birth, and are pre-programmed to devote a significant amount of attention to human faces in particular to gain specific recognition in later development. This specific recognition is enabled by the learning of human faces due to repeated exposure to them, which is where evidence for infants learning to perceive human faces exists.It can be concluded overall that infants to do not perceive faces due to learning or innate pre-disposition to human facial representation alone, but due to a combination of both of these factors.