Developmental psychology
Chapter 5
Perception, knowledge and action in infancy

Introduction

Cognitive development: the development of behaviors that relate to perception, attention, thinking, remembering and problem-solving.

Mental representation: an internal description of aspects of reality that persists in the absence of these aspects of reality.
Traditionally a key aspect of the distinction between perception and cognition.
But, its applicatoin to infancy has not been so productive as once seemed likely.

• Prior to gaining the ability to reflect on absent environments, infants have to learn how to perceive and act appropriately in their here-and-now environment.

Right from birth, infants perceive the world in a sophisticated way, and in the early months they develop perceptual abilities that ‘fill in the gasp’ in perception so that invisible parts of objects are perceived, and that are temporarily hidden are treated as continuing in existence.

Visual perception from birth to six months

Early limitations in vision; are they really a problem?

Visual acuity: the ability to make fine discrimination between the elements in the visual array.

Newborns’ vision is significantly poorer than that of older individuals.
Visual acuity is probably around 1/30th the level of perfect adult acuity.
Young infants have poor control over focusing the eyes (visual accommodation).
These limitations are short lived, both acuity and accommodation improve rapidly during the first 6 months.
Although much of the detail of the visual world may be not available to young infants, these limitations should not affect perception of the larger scale structure of objects.

How can we investigate infant perception?

The visual preference method

Visual preference method to determine whether infants have preferences for certain stimuli. They are shown two objects side by side, and the amount of time they spend looking at each one is then compared.
Such looking time difference is defined as a visual preference. Such a preference implies discrimination, otherwise there would be no basis for preference.
The two stimuli are presented over a series of trials in which left-right associations are systematically varied.

Habituation techniques

If the infant looks for shorter periods over trials, this implies that progressively more of the stimulus has been committed to memory. This if infants habituate they must have form of visual memory.
To investigate visual discrimination.

Shape perception in newborns

Even newborns are capable of perceiving differences between simple shapes such as crosses, triangles, squares and circles.

The components of shape

Newborns can discriminate between different line orientations.

During habituation, young infants have a tendency to process on the basis of the simplest variable.
Even newborns perceive simple shapes as a whole and not just as a collection of parts.

Newborns perceive a three-dimensional world

Size constancy: understanding that an object remains the same size despite its retinal image size changing as its moves closer to or away from us.
Shape constancy: understanding that an object remains the same shape even though its retinal image shape changes when it its viewed from different angles.

Evidence for both shape and size constancy has been obtained with newborns.
Found out with habituation.
Infants respond to a change in true size but not to a change in retinal image size.

Retinal image size: the size of a visually perceived object on the retina of the eyes.

Perceptual development in the first six months

Perception of object unity

Object unity: understanding that an object is whole or complete even though part of it may be hidden.

Common motion is one principle infants use to perceive object unity.

But, newborns do not perceive object unity.
There is a picture of gradual emerge of object unity during early months.

Perception of object trajectories

For example. Whether, if an object moves behind and occlude, the infant fill in the invisible part of its trajectory.

6-month-old perceived traject continuity.
4-month-olds only did when the occluder was very narrow
They perceive trajectory continuity when either the time out of sight or the distance is short.
2-month-olds perceived the trajectory to be discontinuous even with the narrow occluder.

There are age related improvements.

Perception of subjective contours

Subjective contour: when only parts of an object are presented, the remaining contours are ‘filled in´ in order hat the complete shape can be perceived.

This ability develops shortly after birth.

Infants’ perception of people

Face perception

A form of face perception is present at birth.
Infants within a few minutes or hours after birth prefer face-like patterns.
Mechanisms responsible for this preference are in question:

• Two process account: newborn preference for faces stems from an innate sub-cortical mechanism (CONSPEC) that leads newborns to attend preferentially to faces of the same species. After the second month of life, CONSPEC is replaced or supplemented by CONLERN, and experimentally based mechanism that involves a diffuse network of cortical areas and allows for continued cortical specialization and tuning to specific faces.
• Newborns have a preference for certain properties of stimuli that are not face specific.

Discriminating between faces

There is evidence for discrimination between the mother’s and a female stranger’s face by young infants and even newborns with only a few hours contact with their mother.

Preference of attractive faces

2-month-old infants and even newborns will look longer at a face rated attractive by adults than they will at faces rated less attractive.
This preference appears to be driven by the arrangement of internal face features since it is still found when external features are concealed.

Prototypical face: the most typical example of a face. Produced when many different faces are averaged.

Infants may possess an innate ‘face recognition system’ that triggers attention to faces and which is maximally stimulated by a prototypical face.
An alternative possibility is that the attractiveness preference within a few days of birth arises from experience of faces in the immediate postnatal environment. Some kind of facial averaging could provide a learned prototype that attracts more looking.

Perceptual narrowing and face processing specialization

Differences in face experience may explain evidence of growing specialization for faces of particular species, race, gender and age.
Very general abilities become more narrowly tuned as result of experience. This narrowing is likely the result of the extensive social and perceptual experience accumulated with own-race caregivers and other adult individuals within the first year of life.
Preference for female faces is nor present at birth, and is found by three months. This preference develops it only appears for same-race faces.
Interpretation:

• Infants are born with a very general system for recognizing faces, possibly tuned to a very general stereotype, and permitting discrimination of a range of face types, but experience leads to this being replaced by a more specific face system tune to the race the infant encounters.

Imitation

Newborns are capable of imitating facial and manual gestures.
Newborns have no experience of seeing themselves making the gestures, and the suggestion is that this early imitation is based on inter-modal matching between seeing a gesture and the sensation of producing the same gesture.
Imitation may have a very early role in language development. Newborns produce appropriate mouth movements in response to ‘m’ and ‘a’ sounds produced by adults. This occurs even when infants have their eyes closed.
There is an inter-sensory component to these abilities.

Voice perception

Even prior to birth the fetus picks up auditory information.
26 gestation onwards, fetal heart rate changes consistently in relation to auditory stimulation.
There is also responsiveness by 12 weeks gestation.

Newborns reveal the ability to discriminate between certain speech syllables.
Very young infants appear to discriminate speech distinctions that exist in other languages but not in their own, later narrowing their discriminative capacities to distinctions contained in their own language.

Voice and speech discrimination

Newborn infants show an attentional preference for their mother’s voice compared to that of a female stranger of similar age.
Speech sounds are available in the uterine environment and the unborn child learns about auditory information.
Fetuses and newborn infants are capable of encoding speech in sufficient detail to extract differences in rhythm and/or intonation between two passages.

Preference for infant-directed speech

Infants prefer to hear infant-directed speech over adult-directed speech.
Motherese: infant-directed speech, the speech that adults and children over 4 years old use when addressing an infant.
It not only attracts the infant’s attention, but presents clearer examples of speech from which the infant is more capable of learning relationships between words, and objects and actions.

Infant's knowledge of the world

Jean Piaget and the development of object permanence

Piaget’s view was that infants were not born with knowledge of the world, but instead gradually constructed knowledge and the ability to represent reality mentally (constructivism).

Object permanence: the ability to understand that even if an object is no longer visible, it continues to exist.

The ability to maintain a representation of object that are out of sight, leading to awareness of their permanence.
According to Piaget, prior to the age of 9 months, infants do not exhibit object permanence. And although this appears in simple form at 9 months, it does not develop fully until near the end of the second year of life.

Search onset and the A not B error

By 9 months the infant’s reaction to disappearance has changed. Now, if an object is hidden, the 9-month-old would search for it successfully.
This indicated the beginnings of the ability to represent the absent object.
A not B error: an object-searching error that is often made by 8-12 months olds. Infants making this error will look for an object where they have most often found it, rather than where they last saw it hidden.
Piaget took this as evidence that their representation of the hidden object was not yet fully objective, they repeated an old action to ‘recreate’ the object, as if their own actions defined its existence.

Later work on infant cognition

Infants have an awareness of object permanence and an advanced general understanding of the physical world.

The violation of expectation technique

Infants are shown an event and are then shown two new events, on of which is consistent with everyday reality (possible) and the other is inconsistent (impossible). Infants will typically look longer at the impossible event because it violates their expectancies.

Young infants reason about the number of objects in an event

Infants possess core knowledge of the world, on the basis of which they reason about the events that they see.
Infants reason about the number of objects involved in an event.

Young infants discriminate different numbers of items

Infants are capable of discriminating between arrays in terms of numerousity, though only in the case of small numbers.
Subitising: the ability to perceive directly the number of items without consciously counting them or using another form of calculation. This ability only applies to very small numbers.
Infants also appear to be able to discriminate between larger numbers, although in this case they appear to be using a distinct system for detecting approximate differences that only works when the ratio between smaller and larger number is large.

Young infants can count

Young infants have an understanding of addition and subtraction.
When infants saw incorrect numeral outcome, they produced brain activity that matched that obtained from adults when they encounter incorrect outcomes.

Object search revisited

Search failure is not due to lack of motor skill

Infants only have problems with cases where one object conceals another.
This can be because they have difficulty perceiving or understanding the relationship between object and occluder.

Seeking an explanation of the A not B error

Response perseveration?

Response perseveration: Repeating a previously learned response usually when it is no longer appropriate.

Infants make errors even if they have only seen the object hidden and revealed at the A location, and have not been given the opportunity to reach for it.

Memory limitations?

It is possible that infants have more profound memory limitations than adults.

Infants rarely make errors if they were allowed to search immediately for the hidden object at B.
It can be that interference occurred between memory of the object at the first location and memory of it at the new location, such that information about its prior location often predominated over the more recent information about its new location.

Errors occurred even when the object was fully in view at the B location.

Place A as a container

One possibility is that though seeing an object hidden and finding it, infants quickly learn to treat place A as a container, and that it is this knowledge rather than knowledge about the specific object hidden that leads to search errors. And if we consider infant’s everyday experience, it is quite possible that their ideas about containers is to some extent magical.

When hiding took place without overt communication between investigator and infant errors were reduced on B trials.
It is possible that social information has a negative effect on search performance though misinterpretation of the communicator’s message.

Attention

A link has been found between success and continued attention to location B during the delay.
When attention is distracted during the delay perserative behavior increased.

Longer looks and a larger percentage of time spent looking during a focal attention task correlate positively on a looking version of the AB task.

There is a role for individual differences in the likelihood of search errors.
Infants frequently perseverate when they are fully attentive, so inattention is unlikely to be the sole cause of preservation.

Frontal cortex immaturity

The frontal cortex is involved in planning and guidance of action, executive functions.
Diamond claims that immaturity of frontal cortex in early infancy leads to deficits in infant’s ability to use certain types of information to guide action. Infants are unable to use their memory of the absent object to inhibit an old response that is now inappropriate.
There is relevance of the frontal cortex in the AB task. There is an association between successful B trials and greater frontal EEG activation.

Converting knowledge to action

When faced with the A not B task, infants are aware of the continued presence of the object, but are simply unable to use this information to guide action.
Initial success at finding the object at A is based on trial and error manipulation of the cover at which it disappeared rather than knowledge of the existence of the object. And they repeat this action whenever and wherever the object disappears, and even if the objects is placed in view at the B location.
Development of frontal cortex involves formation of links between object knowledge and action, leading to accurate search based on knowledge of the object’s position rather than trial and error.