Female and male responses to cuteness, age and emotion in infant faces

Abstract

Neonatal features in the newborn are thought to trigger parental care, the most fundamental prosocial behaviour. The underlying mechanisms that release parental care have not yet been resolved. Here we report sex differences in the ability to discriminate cues to cuteness despite equivalence in the capability to discriminate age and facial expression. These differences become apparent in a task where adults were asked to choose the cuter of two babies. While women could reliably choose the cuter infant, men had more difficulty in doing so. When showing the exact same face pairs but asking to choose the younger or the happier baby, there was no sex difference. These results suggest that the sex difference in the ability to discriminate cues to cuteness in infants underlies female-specific emotive responses. We argue that this reactivity expressed by women evolved to ensure that a female allocates her caretaking resources to her youngest offspring while it needs mothering care.

Introduction

The cuteness of an infant face is most likely determined by pedomorphic features. These have been thought to function as a stimulus configuration which evokes positive emotions and caring behaviour towards the infant. Lorenz (1943) proposed the concept of the Kindchenschema as an innate releasing mechanism for caretaking behaviour and affective orientation towards infants, triggered by features such as protruding cheeks, a large forehead and large eyes below the horizontal midline of the skull. Baby faces showing these features are commonly described as cute or attractive (see also Sternglanz, Gray, & Murakami, 1977).

Literature on perception of infant faces is scarce. Even fewer empirical studies have investigated the physical properties of a cute baby face. These studies found that exaggerated head sizes are perceived as cuter (Gardner and Wallach, 1965, Hückstedt, 1965). One study reported that preference for babyish head shapes was more pronounced in females than in males (Hückstedt, 1965), while other studies failed to find this difference (Gardner & Wallach, 1965). Hildebrandt and Fitzgerald (1978) investigated whether infant cuteness influenced looking behaviour, facial muscle activity and skin conductance, and found that cute babies were generally looked at longer. Additionally, they report that for women zygomaticus activity increased compared to men, but that cuteness did not modulate the activity of facial muscles. A further study (Alley, 1981) showed that a more infantile head shape increased cuteness when head size is held constant, but did not look at the performance of males and females separately. For a review on sex differences in responses to infants see Berman (1980).

Brosch, Sander, and Scherer (2007) examined whether the Kindchenschema captures attention. They used pictures of infant and adult humans, cats and dogs to test whether infant faces capture attention more than adult faces. They found that photos of human infants capture attention more than photos of adult faces. Furthermore, they found this effect only for stimuli presented to the left visual field, suggesting an advantage for the right hemisphere. Finally, this effect was specific for human stimuli; puppies and kittens did not capture attention more than adult cats and dogs. They found no sex difference, suggesting that infant faces are biologically significant for men and women and are therefore prioritized by the attention system.

In the present study, we take a closer look at the general sensitivity of adults towards baby faces. A recent study found that women showed greater sensitivity to infant cuteness than men (Sprengelmeyer et al., 2009). The difference was enhanced in females taking hormonal contraception and was diminished in postmenopausal women. This suggests a role of the hormones progesterone and oestrogen in mediating sensitivity. But do these sensitivity differences derive from a distinction in perceptual processing? Are men perceptually less sensitive to infant faces? If so, women should perform at a higher level compared to men in other visual judgments about infant faces. Alternatively, women might be more responsive to infant cuteness due to their special biological role in infant care. For example, only females are able to breastfeed and therefore may have developed specific emotional reactions towards infantile cues. Here we explore possible differences between males and females when observing infant faces and specifically test whether sex differences occur for other discrimination tasks such as age or mood discriminations.