Perceptual Development: Attention

Development of Attentional Processes

Arousal refers to the engagement and maintenance of attention in the service of information acquisition, cognition, or behavior. Psychophysiological measures, specifically changes in heart rate, have been combined with simple viewing paradigms to examine changes in arousal and sustained attention. Heart rate changes during sustained attention and attention termination have provided researchers with important information about the early postnatal development of the arousal system. There is generally a slowing of heart rate during the attentive or vigilant state. This returns to baseline levels at attention termination (i.e., inattentiveness even as the subject continues to look at the stimulus). This highlights the idea that attention is more than vision. Many of us can recall a situation in which we are watching a television show but cannot recall anything that happened. The extent of arousal is reflected by the extent of heart rate deceleration during sustained attention. Between three and six months of age, infants show greater heart rate deceleration during sustained attention and simultaneously behavioral indication of better performance on a variety of measures (e.g., more effective information acquisition).

The orienting system has also been heavily studied in infancy. For example, infants as young as two months of age can learn to direct eye movements to anticipate the appearance of a picture in a particular location in space. This requires shifting focus to a location in the absence of something to look at. By definition, this is beyond the scope of simple alerting. Spatial cueing paradigms have been used most extensively to examine the development of overt and covert orienting. In general, attention is engaged with a centrally presented attractive stimulus. A brief peripheral “cue” stimulus is flashed on a screen positioned in front of the infant, to the right or to the left of center. If an eye movement or saccade is allowed to the peripheral cue, the paradigm is considered to index overt orienting. If the cue is too brief to elicit an eye movement, the paradigm is measuring covert orienting. After a delay interval, the peripheral cue is presented by itself either in the same location (valid trial) as the flash or in the opposite (invalid trial) screen location. Changes in the speed of an eye movement, or the frequency of looking in very young infants, to the target as a function of a previous cue are taken as indication that an attentional shift was made to the flashing peripheral cue. Eye movements to the target will be faster, or more frequent, on valid trials relative to invalid trials when the delay between presentations is short. That is, responses are facilitated by the appearance of the peripheral cue. However, they will be slower, or relatively infrequent, if the delay between cue and target presentations is long. This effect has been called inhibition of return (IOR). In the case of overt spatial cueing, IOR has been reported in newborn infants. Inhibition of return following covert shifts of attention may begin to emerge at around three months of age but is not observed consistently until six months. The IOR effect is considered to play a role when infants search the visual environment, prohibiting eye movements to previously examined locations. This would theoretically have the effect of maximizing the number of locations targeted in a visual scene. Indeed, IOR is a putative mechanism at play in tasks that are specifically designed to examine how infants scan the visual world.

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