Even newborns attend to soft sounds and visions. Their bodies become more still, they stop doing what they were doing (like sucking), they open their eyes more and the heart rate slows down. These changes in behavior seem designed to optimize the baby's disposition to receive the stimuli. They are described as orientation reflexes and can be seen, for example, when newborns attend moving lights, gradually changing sounds, or low frequency sounds. However, if the physical stimuli are too intense or the changes too sudden, the children close their eyes and are agitated and their heart rate increases. This is a protective reaction called defensive reflex. Reflections of orientation and defensive reflexes seem to be the most primitive forms of positive and negative attention of the baby.
However, researchers are generally more interested in the development of selective attention, the ability of the baby to focus on one stimulus more than another. Even newborns have the ability at least of a simple form of selective attention, since they choose to look at images of intermediate levels of brilliance and variability of drawings or patterns better than extreme levels and to sheets with drawings rather than to sheets without drawings.
Newborns also moderate their sucking to hear their mother's voice more than the voice of an unknown woman.
What controls the baby's attention? From birth to about three months, babies pay attention to models that contain contours and movement. Between 3 and 12 months they attend to things that seem surprising or discrepant about what they already know. From 12 months on, children pay attention to the events that encourage them to form hypotheses, or guess what is happening in the world.
It is interesting to note that even small children differ from one another in their attention-paying activity, which will be stable over time.