Similarly to the interest observed in Fantz’s studies to the face stimuli, it’s plausible that the importance of attending to a ‘motherese’ speaking figure is not lost on a baby however young they are and that the innate ability is to recognise voice patterns most often associated with a primary carer. In studies by Singh et al. , (2002) it becomes clear that the positive emotion conveyed in ‘motherese’ is highly important to elicit a response in the infant.
Less positive ‘motherese’ was less interesting to an infant than happy adult conversation suggesting that the preference is more attributable to the positive emotion conveyed by vocal affect. DeCasper and Fifer (1980) proposed that differentiation is highly implicated in mother – infant bonding and that this bond may be best served if babies could recognise their own mother’s voice. This being the case, the ability should be evident from birth and in order to test the theory, DeCasper and Fifer conducted a series of experiments in which infants could control what they listened through variation of sucking bursts on a non-nutritive nipple.
Recordings of mothers and unfamiliar females reading an identical passage were used as stimuli through earphones. Baseline intervals between sucking bursts under silent conditions had been established and by varying the interval between the sucking burst, the infant could display a preference for certain auditory stimuli. The subjects in these studies were raised in a group nursery and had limited contact with their mothers. Despite this, the results showed that new born infants can discriminate between speakers and demonstrate a preference for their own mothers’ voice.
One could conclude that recognition of a mothers’ voice doesn’t require learning and must be innate but it is already known that a prenatal auditory ability exists. The subjects in these studies could simply have learnt to recognise voices before birth. DeCasper and Spence (1986) used the same technique to test infant responses to passages that they were read to in utero. After birth, the favourable preference displayed to the familiar piece versus a passage never before heard did suggest that there is some auditory learning that takes place before birth.
In order to produce robust evidence, science mandates a rigid structure to experimental design but the nature of the development of perceptual ability relies on an integration of information from different sensory modalities thus limiting the isolated sensory experiments looked at this far. Adults naturally coordinate vision and auditory information by looking towards the source of sound and associating voices with people whose lips are moving. Morrongiello et al. , (1998) habituated newborns to toy – sound combinations to establish whether they could learn this cross modal integration.
The results concluded that infants can learn sight-sound pairings and that they expect them to remain co-located. In a later study by Slater et al. , (1999) non contingent and contingent experimental situations were created where the auditory stimulus was presented regardless of visual attention or contingent on subject visual interest. The results showed that babies learned the sight – sound pairings in the contingent setting and it is the presence of contingent information that governs learning of arbitrary audio-visual combinations.
These types of studies that examine perception from a more holistic approach bring up some interesting questions. If baby’s perceptual learning is improved in a cross-modal situation, what other perceptive senses are linked and is there anything more to learn from individual sense studies alone? That research has aided the understanding of perceptual development is evident. However limited, experiments into individual sensory areas have changed opinion on the perceptive functionality of an infant at birth and proved a capacity greater than some theorists might have earlier believed.
Importantly, it would appear that the functioning is improved greatly if the studies utilise stimuli that are similar to an everyday experience for an infant. To the extent that these abilities are innate or learnt is not absolute from the studies investigated here but the evidence points towards the conclusion that some areas of perception are learnt and some innate, with the innate preparedness being easier to deduce from ecologically valid experiments with socially familiar stimuli.