A newborn baby often sees many faces pass by above their crib. Although the visual system is not fully developed at birth, babies develop a preference for the mother's face within a few weeks. However, the extent to which babies are aware of the stimuli around them remains to be determined. Because babies cannot share their experiences with us, it is difficult to answer this question. Nevertheless, by making use of EEG it is still possible to try to figure out what babies perceive.
To distinguish conscious perceptions from unconscious perceptions, so-called masked stimuli are often used. For example, an image of a face is shown for several hundred milliseconds, immediately followed by another image. The latter image acts as a "mask" of the previously shown picture. In research it may be an image of a distorted figure of the same size and shape as a face, which is not recognizable as such. By varying the timing and duration of the mask stimulus, a subject will sometimes consciously perceive the image of the face and sometimes not. While performing such a task, the brain activity can be captured with the help of an EEG. In adults, it has been shown that peaks in EEG brain activity can only be measured when a person indicates that they have consciously perceived the stimulus.
The above research design has now also been applied to infants aged 5, 12 and 15 months. In all age groups the same EEG characteristic of conscious perception was measured, as has also been found in adults. In the youngest infants, however, this response was very weak and delayed. In the older infants, the response was stronger and also occurred earlier. It therefore seems that the brain mechanisms responsible for conscious perceptions are present early in development. However, these processes still need to develop further, as shown by the slow response in the younger infants. This may be because myelination is still in full swing or because certain connections between brain regions have yet to form. Myelination is a process during brain maturation in which a layer of fatty material forms around the part of a neuron which transports signals to another neuron. This helps our brain to send information faster to other brain parts.
Nevertheless, the authors of this study emphasize that the results say nothing about the subjective experience of the babies. We can only speculate because verbal communication of babies is needed for that. It is therefore going too far to say that babies have memories, feelings or associations when seeing a face.
This research was published in Science on April 19, 2013.
Author: Bart Aben (translated and edited by Sophie Ruppert)
Originally published on Brainmatters: May 8th, 2013