It is important to study infants as this might help predict outcomes later in life. Early development lays the foundation for later life (e.g. malnutrition in infancy can lead to obesity in later life). Early trauma has cascading effects. It is possible that cognitive processes can be predicted by using outcomes in infancy. Early intervention and prevention are more effective than later interventions.

Infants are extremely sensitive to learning. During infancy, there are fast-growth processes in both the body and the brain. Sleep and sleep quality are associated with good outcomes in infants. It is thus important for infants to learn how to sleep well and not learning this has cascading effects.

It is difficult to study infants because regular research methods do not work. However, there are several standardized tests to study infants (e.g. Bayley’s scales of infant development). The standardized tests have several disadvantages. The standardized tests are time-consuming (1), require much training (2) and are not very reliable (3). Using parent measures is not measuring the infant, which is a disadvantage.

There are two main methods of studying infants:

1. Visual preference method
   This method assumes that a longer looking time indicates a preference or an interest. Besides that, it is assumed that a longer looking time indicates that the infant is able to distinguish the stimulus of interest from other stimuli. This method can be used to examine what infants can perceive and what infants know. 
2. Habituation-dishabituation method
   This method presents an infant with repeated presentations of the same stimulus. A decrease in looking time is seen as habituation. It is believed that an increased looking time upon the presentation of a novel stimulus (i.e. dishabituation) is indicative of being able to distinguish the stimulus of interest from other stimulus and gives insight into the knowledge of infants.

Looking behaviour is used to study infants because it is available in infants early on (1), because saccades and looking behaviour is more under voluntary control than their arms and legs (2) and because visual acuity develops almost completely before three months of age (3).

A modern technique to study infants is the eye-tracking technique which uses a light to illuminate the eye (i.e. infrared light). A camera films the eye and an algorithm detects the corneal reflection and this determines eye gaze position. This data needs to be processed in fixations and saccades. Heart rate measures could also be used to study infants as a higher heart rate is associated with changes in attentional status.

The gaze patterns of adults depend on the instructions given to the participant. The eye-tracking technique can also be used to identify strategies when solving problems (e.g. children doing arithmetic problems).

There are different stages of attention development in infants:

1. Alertness, wake-sleep cycles
2. Spatial orienting (i.e. engagement, disengagement, shifting)
3. Object attention
4. Endogenous control

The looking time of infants appears to be related to cognitive functioning at a later age. This is explained by stating that the difference in looking time is related to a shift from global to local attention (1) or that the difference in looking time is related to overall processing speed.

The long looking infants do not appear to be good at feature discrimination. However, when given enough time, the long lookers are able to discriminate different features. This breaks down in global discrimination if they are given less time. Short lookers have more efficient information processing abilities when compared to long lookers. This is associated with later executive function measures.

The fixation durations and the saccade amplitudes decrease with age. The horizontal bias refers to adult eye movements being generally more horizontal than vertical. The central bias refers to attention always starting in the centre rather than in the periphery (i.e. especially for adults).

The determinants of infant attention allocation are general exploration strategies (1), perceptual factors (2), cognitive factors (3) and individual differences (4).

Infants tend to look longer at locations where adults look at. Infants that are better at visual search have faster-decreasing fixation durations. Furthermore, infants that are better at inhibition have decreasing fixation durations. There appears to be a competition between endogenous and exogenous control.

Marker tasks make use of behavioural tasks and check the performance on the same tasks at different ages in different contexts to provide insight into the interrelations between developmental changes in observable behaviour and brain structure. However, these results are difficult to generalize as it may be mediated by different neurological structures at different stages of development.

Overt orienting refers to shifting one’s gaze from one location to the other. Covert orientation refers to shifting attention without shifting gaze or body. Exogenously controlled shifts of attention refer to automatic shifts of attention (e.g. loud noise). Endogenously controlled shifts of attention refer to voluntary shifts of attention. However, initiation of attention shifts includes both endogenous and exogenous components. The visual grasp reflex (i.e. attention-getting reflex) refers to automatic saccades as the result of the sudden onset of a stimulus in the peripheral visual field.

In infants, looking away is preceded by the disengagement of attention and gaze. Young infants have difficulty looking away from a stimulus once their attention has been engaged. This is expressed in periods of long staring and is called obligatory fixation.

The degree of disengagement difficulty varies between situations as the probability and latency of infant’s shifts of gaze from a stimulus currently under attention to a target in the periphery are influenced by higher-order characteristics of the two stimuli. During fixation of a stimulus, rapid shifts of covert attention take place to select the next location to look at. The response facilitation effect refers to perceptual processing of stimuli at the previously attended location being enhanced for 300ms. A longer interval leads to the reverse pattern and this is the inhibition of return.

Once an infant orients on a stimulus, the infant will scan it. They examine limited parts of the stimulus and spend long periods fixating a few single locations and ignore other stimuli in the visual field. They will look at the most salient parts of a stimulus (e.g. edges) (i.e. externality effect). Around 4 or 5 months of age, eye movements are generated in accordance with the strategic demands of ongoing information processing.

The anterior eye movement control system is responsible for saccades that are voluntary or planned. The posterior eye movement control system is responsible for saccades that are fast and reactive. Both systems control the activity of the superior colliculus. Bronson’s model states that early development of visual attention can be viewed as a shift from subcortical to cortical processing as subcortical processing is the most mature at birth.

Self-regulation refers to maintaining a stable or desirable state by modulating affect, behaviour and cognition (e.g. drinking to prevent thirst). Self-regulation abilities and behaviour in infants is related to later life outcomes. In young children, it is typically tested using the marshmallow test. Infants engage in self-control by looking away from intense or annoying stimuli. Infant’s ease of disengagement is associated with their level of distress when faced with limitations. Attentional processes affect infant’s regulatory skills and social behaviour.

The development of self-regulation builds on simpler cognitive skills (e.g. visual attention). Attention processes consist of three neural networks which are closely related to self-regulation.

1. Alerting network
   This network is involved in achieving and maintaining attention.
2. Orienting network (most important during infancy)
   This network is involved in selecting input.
3. Executive attention network (most important after 3 or 4 years)
   This network is involved in executing control over the alerting and orienting network.

Longer fixation and less variation in fixation predicts better effortful control. However, compliance in toddlerhood is not predicted by visual attention measures. Longer fixations may indicate better executive function because of the enduring conflict between maintaining and disengaging attention. Less variation of fixation may indicate cognitive maturity.