Infant Development

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This area focusses on infants aged 0 - 18/24 months.

Infants cannot physically tell us what they are thinking, we must find ways of understanding them. To be able to understand how an infant thinks we must look at perception and cognition:

  • Perception involves basic processing of sensory information
  • Cognition involves the extraction of meaning and understanding from this information

therefore; Cognition operates on perception. The information about an infant's perception and cognition is collected through the window of their behaviour.

In experiments we may use various techniques to measure infant perception; looking time, sucking-rate, heart rate, head turns, neuroimaging and eyetrackers

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Can infants distinguish between 2 or more stimuli?

A change in reaction usually deduces discrimination towards a stimulus but absence of reaction does not mean lack of discrimination. Pascalis et al (2002) found that babies could discriminate between primate faces, something that adults are not very good at. Older babies (+ 9 months) refused to look at the new face because they were bored.

When a child is exposed to the same stimulus repeatedly they will become bored and habituation will occur. If a new stimulus is introduced, infant's attention will return to initial levels.

Habituation can be used by a fixed number of sets or by measuring the decrease in reaction to the stimulus.

Habituation basically means that the infant is becoming desensitized to a stimulus, the habituation method relies on the observation that infants have a preference for new stimuli but it is worth noting that they also have a preference for complex and human-like stimuli.

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Piaget believed that children are blank slates with absolutely no understanding of numbers. To Piaget, cognitive development was a progressive reorganisation of mental processes resulting from biological maturation and environmental experience (Learning & Growing)

Opposing Piaget are Nativists who claim that children may actually have an ancient numerical system that gifts them with numerical skills.

Researchers at Boston College have demonstrated that infants who are shown 2 screens filled with a number of objects whilst drum beats are being played will look longer at a screen whos number of items corresponds with the amount of drum beats.

McGarrigle et al, 1974 also exposed children to two rows of candy and asked which row had more, children who answered this correctly changed their answer when one row was spread out, they believed the stretched row now had more candy even if it had less however, children who were asked "which row would you like to eat?" Usually choose the row with more candy no matter which row was stretched. So does the way we test children in a verbal sense have an effect on results and was Piaget wrong about children being merely blank slates?

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Wynn, 1992

5 month old infants were seen to calculate the results of simple arithmatical operations on small numbers of items. This indicates that infants may hold true numerical concepts and that we could be born endowed with numerical abilities.

Experiment 1 : A looking time procedure was used on 2 groups of 32 infants.

The '1+1' group were shown an object within an empty display area. A small screen was then rotated up, hiding the item from the infant's view. A second identical item was seen being placed behind the screen (Infant sees the process but not the result). The screen is then lowered. The '2-1' group consisted of similar events, however an item was subtracted from behind the screen instead.

Infant looking time was recorded. Before test-trials infants were shown the scenario 6 times in order to record baseline looking time. It is assumed infants look longer at unexpected events, if able to compute numerical results looking times will be longer for incorrect results than correct results. Both groups looked longer at incorrect results.

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Wynn, 1992 (2)

Experiment 2: Replication of experiment 1, smaller number of objects, same pattern of results obtained.

Infants know that an addition or subtraction results in a change in the number of items but is there another explanation for this success?

It is possible that infants are calculating the results of the addition and subtraction as a continuous amount of physical substance but there has been no evidence to support that infants are sensitive to small differences in physical matter.

Cohen & Marks (2003) disagreed with Wynn's results, they believed that children did not look longer at the impossible outcome because they were surprised but because it was familiar to them. Research suggests a curvolinear relationship between looking time and stimulus discrepency. At the beginning, when infants are still habituating to a stimulus, familiarity outweighs response to novelty so...

Perhaps Wynn did not habituate her infants sufficiently.

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Other Problems with Wynn

When a number varies so does the surface area, length of contours and density of the items in the area.

What is it that the infant is dishabituating to? It has been found that infants increased looking time in response to contour length and not to number. Need to be careful this is not what the infants are focussing on.

It may be better to include other possible factors into the habituation process (Xu & Spelke, 2000). Infants were habituated to 8 dots that changed surface area and density on each presentation. Infants presented with 8 to 16 dots, with habituated density and surface area, showed dishabituation due to number.

When it comes to numeracy in infants we can never be too sure. We have to consider that looking time is the measure used which may need to be used carefully as it can be influenced by a range of factors already discussed. We also have to ask the question if infants are really using numeracy or are their attentions focussing on things like surface area.

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Object Permanence

The understanding that an object does not simply disappear when hidden.

Piaget (1963) used looking behaviour to test object permanence as it is believed to be part of the sensorimotor stage of development.

The Development of Object Permanence;

0-1 month - Out of sight out of mind

1-4 months - Where did it go?

4-8 months - Looks for partially hidden objects

8-12 months - Looks for hidden objects where they were previously hidden

12-18 months - Looks in a new hiding place/can't deal with objects that move when hidden

18-24 months - Looks for objects that have been hidden and moved.

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Baillergeon et al, 1985

Infants were habituated to watching a drawbridge move back and forth. A solid object was placed behind the drawbridge in its path of movement which provided 2 test events; 

  • Possible event - Drawbridge moves down, hiding the box & then retrieving showing that the box is still present.
  • Impossible event - Drawbridge appears to travel unobstructed through the obstacle.

Results: 5 month old infants showed surprise (indexed by looking time) when they saw the screen apparently travel unobstructed through the obstacle.

Conclusion: 5 month old infants seem to realise that a solid object is a permanent obstacle despite its invisibility.

Baillergeon et al concluded that babies know about object permanence at this age but cannot act on their own knowledge. Getting children to look for an object leads to an underestimation of what they understand.

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Problems with Baillergeon et al

Problem with habituation:Does an infant look longer at the impossible event because it has acquired object permanence or becuse it is a novel event? Habituation confounds cognitive ability with a general reaction to novelty, in the presence of a block, in the degree of rotation of the bridge.

Solution: Take novelty out of the equation and habituate infants to all events.

Bogartz et al (2000) conducted a replication study of the 1985 study with five and a half month olds used events for both habituation stage and test allowing the investigation into familiarity and novelty.

After replication it was found that looking time in the drawbridge experiment was determined by novelty and familiarity, not possibility. Infants with fewer familiarisation trials were more likely to prefer a familiar rotation event, object permanence is now questioned.

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Goal Directedness

Do infants understand behaviour? That certain movements are directed towards a goal?

Goal directedness would imply intentionality (behaviour is intentionally adjusted in order to reach the goal) and rationality (behaviour is one that leads most directly to the attainment of the goal) amongst infants.

Reports a habituation study indicating that 12 month old infants can take the "intentional stance" in interpreting the goal-directed spacial behaviour of a rational agent.

Is has been theorised that in the fifth year of life a young child applies a relatively sophisticated mentalistic interpretational strategy to explain and predict the behaviour of other agents.

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Gergely et al, 1995

In this experiment, infants observe 2 sequences involving the behaviour of two simple figures (a small circle and a larger circle) positioned at a distance from one another with a rectangle placed in between them. The large circle expands and contracts, returning to its original size and then the smaller circle repeats this movement. After this is repeated a second time the small circle rolls towards the large circle following the shortest path which will allow them to connect however, it stops in front of the rectangle which is clearly obstructing its path. The small circle returns to its original position and starts again, this time jumping over the obstacle, approaching the large circle where they make contact. Circles again repeat the expansion/contraction routine.

By hypotheses, repeatedly viewing the sequence of events explained should allow the infant to interpret the small circle's behaviour as that of a rational agent with an intention to approach its goal.

Sequence 2 places the rectangle behind the small ball so that it is no longer in the way. There is already a more rational means goal available so infant should abandon her interpretation of the small circle's behaviour as a rational agent.

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Gergely et al, 1995 (2)

Following the habituation phase, both groups of subjects were presented with two types of test events. It was believed that by the end of their first year, infants are able to interpret the goal-directed behaviour of rational agents supported by the dishabituation of infants seeing sequence 1 when faced with a new situation they would be able to generate an excepectation about the most rational new means action the agent would be likely to perform to reach its goal.

The fact that subjects showed less surprise at new action indicates that they were able to predict this as the most rational means action likely performed in the new situation.

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Intentional People

Gergely et al (2002) replicated a previous study (Meltzoff, 1988).

14 month old infants watched an actor turn on a lightbulb with her head. 1 week later it was found that two thirds of the infants showed deferred imitation of using their heads to switch on a lightbulb.

The use of the head is surprising given that one year olds apparently understand rationality therefore, infants would be expected to re-enact an action only if it seemed to them the most effective means to acheive the goal.

If infants noticed that the demonstrator did not use her hands they may have inferred that the head action must offer some afvantage in turning on the light.

This study had 2 conditions; Hands occupied, hands free. "Claimed rationality has to be evaluated in relation to the constraints of the situation". If the lightbulb was turning on and the children noticed that actor's hands were free they were more likely to try it.

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So Infants are Rational?

Infants are able to infer intentions and link behaviour to these intentions therefore they should be able to pereive people as agents with a mind, who will act in accordance with their intended goals.

Theory of Mind (ToM): The ability to appreciate that others have a mind of their own. Traditionally people believe that a theory of mind emerges around the age of 4 or 5. Do younger infants have ToM?

Studies have been conducted in order to test children's ability to predict an actor's behaviour on the basis of her true or false belief about a toy's hiding place (Sally-Anne Task). Onishi & Baillergeon (2005) have conducted a similar experiment using 15 month old infants.

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Onishi & Baillergeon, 2005

Infants received three familiarization-trials.

At the beginning of the first trial a toy watermelon rested on the apparatus flood between two boxes (one yellow, one green). The actor played with the toy and then placed it inside the green box. During the second and third trials the actor reached into the green box as though to play with the toy, paused and a screen was dropped to hide the scene.

Next infants received a single belief induction, there were 4 versions of this trial, 2 true belief and 2 false belief conditions;

  • Child & actor watched yellow box approach green box & return to original spot = no change
  • Child & actor watch toy move from green to yellow box
  • Only child sees object move to yellow box
  • Child & actor see toy move to yellow box but actor leaves and toy is returned to green box
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Onishi & Baillergeon, 2005 (2)

Test trial:

Child sees actor reaching into either yellow or green box.

Planned comparisons indicated that, in each of the four belief conditions, infants expected the actor to search for her toy where she believed it to  be hidden and looked longer when she did not.

These children already possess a theory of mind when the test is not verbally confusing.

In support of this a replication study was conducted (Senjo et al, 2009) using eye-trackers in replacement of looking time and confirmed that 24 month old infants looked at the box consistent with the actors belief even before the actor made the movement to reach for the object.

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It is unclear whether young infants understand concepts of number or object permanence, it is clear that they are able to attribute goal directedness and intentional behaviour to animated objects and people.

Attention and memory are highly important!

In order to encode a sequence of goal-directedness movement, the infant needs to be able to sustain its attention for the duration of the episode. As well as this in order for the infants to understand false beliefs the infant needs to remember what the actor has seen.

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