PBS Lent Developmental Psychology

This lecture will consider the major theoretical frameworks for considering cognitive development in children, those of:

Piaget, Vygotsky and Bowlby

What kinds of knowledge are central to human cognitive development? One proposal is that there are 3 basic domains of knowledge, [blank]. Information about these domains can be gained by looking at and listening to the world of people, objects and events, and (as motor skills develop) by acting on the world and learning about the consequences of these actions.

naïve physics, naïve psychology and naïve biology

The major theorist of human cognitive development is still [blank], who worked at the University of Geneva from the 1950s onwards. His experimental paradigms for measuring children’s cognitive development have shaped the field, and his creativity and observational powers were immense.

Jean Piaget

Although his main thesis has been disproved – which was that [blank] – his theory still stands as the main organisational construct in the field. The Piaget Institute in Geneva is still going strong.

there are a sequence of stages in children’s cognitive development, and that children do not think and reason in an adult-like fashion until the teenage years

Piaget was by training a biologist, and in his theory the primary causal mechanism for building knowledge was [blank] Knowledge was constructed by the child as a consequence of their active experiences of the external world.

the adaptation to and refinement of existing cognitive “schemes” (or knowledge structures) by the environment.

Piaget suggested that the cognitive system would naturally seek equilibrium, and that cognitive development was caused by two processes. These were:

accommodation and assimilation

Accommodation was:

the process of adapting cognitive schemes for viewing the world (general concepts) to fit reality.

Assimilation was [blank]. As every cognitive equilibrium can only be partial, every existing equilibrium (stage) must evolve towards a higher form of equilibrium (stage) - towards a more adequate form of knowing. This process of evolution was thought to drive cognitive development.

the complementary process of interpreting experience (individual instances of general concepts) in terms of current cognitive schemes

Piaget proposed four major cognitive stages in logical development, corresponding to four successive forms of knowing. These were:

sensory-motor cognition, pre-operational cognition, concrete operational cognition and formal operational cognition

During each of these stages, children were hypothesised to think and reason in a different way. Each stage was thought to require fundamental cognitive restructuring on the part of the child. Subsequent experimental work has shown that:

children can “pass” the tasks intended by Piaget to capture the fundamentals of reasoning in each stage at earlier ages than envisaged in the original theory

A key insight for the field has been that 'pure' measures of reasoning, in which logical abilities are measured independently of the context in which they are required, [blank] Similarly, in certain contexts, adults can appear to lack basic principles of logic.

are more or less impossible to devise. When familiar, 'child-centred' materials are used, and when attention is paid to linguistic and non-linguistic aspects of the experimental set-up, then even very young children may pass tasks assumed to test the abilities of adolescents.

The second core theory in cognitive development is that of [blank]

Lev Vygotsky

Vygotsky focused on [blank] in cognitive development. While Piaget focused on how the individual child constructed knowledge for herself,

the complementary roles of language and of culture

Vygotsky argued that knowledge originated in socially meaningful activity. Knowledge was also shaped by:

language. Language played an essential role in the organisation of ‘higher psychological functions’ such as reasoning. Language was seen as the primary ‘symbolic system’ that children could respond to psychologically. Language hence mediated cognition.

Vygotsky argued that cognition developed prior to language, as demonstrated by the cognitive activities of babies. However, ‘the most significant moment in the course of intellectual development .. occurs when speech and practical activity, two previously completely independent lines of development, converge’. This convergence was marked by:

egocentric or inner speech. Inner speech was seen as fundamental in organizing the child’s cognitive activities.

Vygotsky argued that language was as important as action in attaining goals, and that language and action were part of ‘one and the same complex psychological function’:

Language enabled children to disconnect themselves from the immediate, concrete situation and to generate possibilities and plans for solving problems. Language was also thought to play a role in controlling the child’s own behaviour. For example, by speaking of her intentions, the child guided her actions. Finally, language enabled children to ask adults to help them, thus acting as a problem-solving tool.

The importance of learning from others to cognitive development was recognised in the concept of the ‘zone of proximal development’. While acknowledging that it was important to measure a child’s actual level of development, for example via tests of mental function, Vygotsky argued that it was important also to investigate:

how much further a child could go under the guidance of a teacher. He gave the example of two children who entered school aged 10 years, and who could deal with standardised tasks up to the degree of difficulty typical of the 8 year level. These two children would have a mental age of 8 years. However, suppose the experimenter then showed them different ways of dealing with some of the problems. Suppose that with assistance one child could deal with problems up to a 12-year-old’s level, the other with problems up to a 9-year old’s level. Vygotsky argued that mentally these children were clearly not the same. They differed in terms of their zone of proximal development (ZPD).

Vygotsky argued that the ultimate natural ZPD was:

play. Play and the world of the imagination fulfilled a crucial psychological function in development. For example, play enabled children to realise desires that could not otherwise be fulfilled (e.g., being the mother).

Vygotsky argued that the defining characteristic of play was:

the creation of an imaginary situation. Play was not simply symbolic, because of the role of motivation. Play also involved rules of behaviour, hence supported the development of self-regulation. Vygotsky argued that play provided a critical bridge between the perceptual/situational constraints of early childhood, and adult thought, which was totally free of situational constraints.

Thirdly, we consider the theory of John Bowlby, who recognised the important role of emotional and social experiences in development. He argued that:

a ‘warm, intimate and continuous’ relationship with the mother (or other primary caregiver) was essential for mental health. At birth infants prefer the mother’s voice and the mother’s smell, as these are most familiar

However, the important factors in becoming a ‘preferred attachment figure’ are:

proximity and consistency. Babies quickly learn to prefer the faces, voices and smells of their most consistent and warm caretakers. These specific attachments are very important for healthy psychological development.

Bowlby argued that the [blank] are critical for the development of children’s “internal working models” (psychological expectations) of their value as a person who is deserving of love and support from others.

consistency of early attachment experiences

If these interactions are characterised by consistency and warmth, the baby is described as showing:

“security of attachment”

If an infant consistently experiences caretaking that fails to be contingent on their needs, or that is not characterised by warmth, then the attachment is said to be:

“insecure”.

Similarly, if an infant consistently experiences caretaking that is erratic and neglectful, so that sometimes caretaking is contingent on their needs and sometimes it ignores those needs, attachment is also:

insecure

Infants who are insecurely attached to their caregivers still prefer those caregivers over other people. The term “insecure attachment” refers to the fact that the [blank] Mary Ainsworth, a student of Bowlby, devised the ‘strange situation’ to enable the experimental measurement of attachment security.

infant cannot rely on those caregivers responding appropriately to their cries and smiles - or responding at all.

Two main types of insecure attachment are identified in the literature. [blank] infants appear to become resigned to their fate. They develop self-protective strategies, such as not seeking contact when the carer is close, as though to protect themselves against disappointment.

“Insecure avoidant”

[blank] infants become very clingy and fight against separation, as though trying to force appropriate caretaking behaviours from the adult.

“Insecure-resistant”

Research shows that both forms of insecure attachment are related to:

less positive developmental outcomes long-term. These include social-emotional outcomes, relating to self-esteem and self-control, and also cognitive outcomes, relating to intellectual and academic achievement.

In extreme cases, usually involving parental reactions that are frightening for the infant, attachment is [blank]. Caretaking is so unpredictable that an infant cannot find a way of organising her behaviour to get her needs met. The internal working model developed in response to such caretaking is often that the child is flawed in some way, and does not deserve love and support from others. Such children are at risk for mental health disorders, including depression, oppositional-defiant disorders or conduct disorders.

“disorganised”

Healthy attachment relationships [blank]. Relationships depend on learning. Learning that your social overtures will be met with contingent responsiveness and warmth are the key factors required for babies to develop secure attachments. Grandparents, foster parents and older siblings can all be sources of secure attachments

do not have to be with the genetic parents

Similarly, research does not suggest that [blank]. The psychological relationship or “bond” that mothers and other caretakers form with infants grows over time, via learning. Consistency, responsiveness and warmth are the key attributes.

separation from the mother following birth (for example, for a medical procedure) prevents “bonding” with the infant

The existence of [blank] in infancy provides a useful index of infant's perceptual abilities as well as of their attentional skills. The existence of a preference implies that the infant can distinguish between different entities.

visual preferences

The 'visual preference' technique was first used by Fantz (1961, 1966), who studied [blank]. However, a 'no preference' result in the visual preference paradigm is difficult to interpret.

simple perception of forms in a ‘looking chamber’ which enabled the tracking of infant gaze

A way of finding out whether infants can in fact distinguish two equally-preferred visual stimuli is to use habituation. [blank] Habituation is assumed to provide a way into infants’ conceptual (cognitive) representations.

The infant is repeatedly shown an object (O1) until looking time falls off. A new object is then shown (O2). If the infant shows renewed looking, discrimination between O1 and O2 is assumed.

In one famous “sucking” experiment (De Casper & Fifer, 1980), newborn babies were given a dummy to suck. First, their natural or “baseline” sucking rate was measured. Next, the infants were played a tape recording of their mother reading a story. Each time their suck rate increased above baseline, the tape would play. Each time the suck rate dropped below baseline, a strange female voice would be heard instead, reading the same story:

The infants rapidly learned to suck fast to hear their mother’s voice. The following day, the experimenters reversed the contingency. Now slower sucking was required to hear their mother’s voice – and the babies reversed their suck rates.

Sucking can also be used to measure cross-modal understanding. Meltzoff and Borton (1979) gave one-month-old infants one of two dummies to suck that had different textures. The surface of one of the dummies was smooth, whereas the other had a nubbled surface. The infants were prevented from seeing the dummy when it was placed into their mouths, and so in the first phase of the experiment their experience of the dummy was purely tactile. In the second phase of the experiment, the infants were shown enlarged pictures of both dummies, and:

the experimenters measured which visual stimulus the infants preferred to look at. They found that the majority of the babies preferred to look at the dummy that they had just been sucking.

Another important infant paradigm is violation of expectation. Infants' ability to process and represent spatial, numerical and causal relations can be gauged by introducing violations of typical regularities in the relations between objects. These violations result in physically 'impossible' events. If infants [blank], this implies an ability to represent the causal structure of these relations (work of Baillargeon)

look longer at the impossible events compared to a control condition

In one famous study, Baillargeon, Spelke and Wasserman (1985) habituated 5 month old babies to a display in which a screen continually rotated through 180' towards and away from the baby, like a drawbridge. Following habituation, a box was placed in the path of the screen. As the screen began its 180' rotation, it gradually occluded the box. When it reached 90', the entire box was hidden from view. For babies who were shown a 'possible event', the screen continued to rotate until it had passed through 120', at which point it came to rest, apparently having made contact with the box. For babies who were shown an 'impossible event', the screen continued to rotate until it had passed through the full 180' rotation. [blank] Baillargeon et al. argued that the babies had represented the box as continuing to exist, even when it was occluded by the screen. So babies aged 5 months had an understanding of ‘object permanence’.

The infants looked longer at the display when the screen passed through an apparently solid object.

Habituation can also be used to explore infant memory. Baillargeon and Graber (1988) showed infants a display which had two possible spatial locations in which a toy could be placed, A and B. The two locations were marked by identical mats. As the infants watched the display, an attractive object was placed at location A (in fact, the object used was a plastic styrofoam cup with matches stuck into its sides). Two screens were then slid in front of the two locations, hiding the mats. A hand then reached behind the screen at location B, and retrieved the styrofoam cup:

This retrieval from B was an "impossible" event. Location B had been visibly empty when the screens slid in front of the mats, so the cup should only have been retrievable at location A. Baillargeon and Graber argued that if the babies could remember the location of the object during the delay, then they should show increased looking at the display.

Baillargeon has used the violation of expectation (VoE) paradigm in many studies of infant cognition, to great effect. However, her research enterprise has not been without criticism. Her critics are highly resistant to the notion that young infants engage in physical reasoning (e.g., Haith, 1998). As they point out, looking paradigms were developed to study sensory and perceptual questions, not cognitive questions. They argued that it is simply not possible to generate perceptually-identical but conceptually distinct stimuli for habituation paradigms (e.g., Sirois & Mareschal, 2002). Such critics argue that Baillargeon:

must be able to discount every possible perceptual interpretation of differences in looking time before proposing cognitive interpretations of infant looking behaviour. Bogartz, Shinskey and Speaker (1997) argued that simple perceptual mechanisms such as novelty, scanning and tracking may explain longer looking times by infants in some perceptual conditions versus others.

Haith (1998) goes further, and suggests that infants may [blank] In other words, there is reduced sensory activity in the same perceptual systems that are active when a real object is present, even though the object has gone from the visual field. Haith suggests that this activity basically reflects degraded sensory representations.

have lingering sensory information about objects that have been (for example) occluded from view, and that it is this lingering sensory information rather than a conceptual representation of the object that yields the changes that can be measured in looking behaviour.

To adjudicate between these views, we need new methods for studying infant cognition, and cognitive neuroimaging provides a range of possible methods. A series of experiments with 6-month-old infants reported by Kaufman, Csibra and Johnson (2003) provides a nice example. Kaufman et al. used [blank] as a way of examining what infant’s “representations” of occluded objects were actually like.

EEG imaging

The EEG (electroencephalogram) is a [blank]. Kaufman et al. recorded EEG when infants were watching different disappearance events involving a train and a tunnel, which were either expected or unexpected. The habituation event was a toy train going into a toy tunnel. The train was shown entering the tunnel, and then reversing back out again. Following habituation, the infants watched the train enter the tunnel, and then saw either (a) a hand lifting the tunnel to reveal the train (expected appearance event); (b) a hand lifting the tunnel to reveal no train (unexpected disappearance event); (c) the train leaving the tunnel and the visual field, and a hand subsequently lifting the tunnel to reveal the train (unexpected appearance event); or (d) the train leaving the tunnel and the visual field, and a hand subsequently lifting the tunnel to reveal no train (expected disappearance event).

measure of brain electrical activation obtained by attaching sensitive electrodes to the scalp

Behaviourally, the infants looked significantly longer at the unexpected disappearance event compared to the expected disappearance event. The EEG data showed:

much higher activity when the train was occluded, on the right side of the brain only. In addition, when the tunnel was lifted to reveal no train (unexpected disappearance), there was sustained EEG activity which peaked around 500 ms after the lifting of the tunnel. Kaufman et al. argued that this increased activity showed the brain attempting to maintain its representation of the train despite the competing visual evidence that the train was not under the tunnel. The finding that EEG activity increased appears to rule out explanations of infant looking based on degraded sensory inputs.

Another useful way of exploring infant cognition is to teach infants [blanl] a causal contingency between a response and a reward (conditioning)

a causal contingency between a response and a reward (conditioning)

In these studies, the conditioned response was kicking, and the reward was the activation of an attractive mobile hanging over the infant's cot. The contingency was that kicking activated the mobile. Activation of the mobile occurred via a ribbon that was tied to the infant's ankle. Infant memory for this cause-effect relation was then measured by returning the infants to the same cot after some time had passed, and seeing how much they kicked in the presence of the mobile. [blank] When given a “reminder” of the contingency (for example, the mobile was activated briefly before the ribbon was tied to the ankle), these very young babies showed memories over gaps as long as a month.

Babies rapidly learned to kick to activate the mobile. A few days later, the babies were put back in the cot with the same mobile. Kicking was again measured, although this time the mobile did not activate. Babies of 3 months still kicked much more compared to their baseline kick rate. This suggested that they retained a memory of the cause-effect relationship. In fact, extra kicking, the index of remembering, could be demonstrated over gaps as long as 2 weeks.

More recently, ingenious ‘memory span’ paradigms have been invented for infants. Rose, Feldman & Jankowski (2001) measured how many items could be held in mind by infants by testing the same babies when they were aged 5, 7 and 12 months. The infants were shown 3 18 February 2025 colourful toy-like stimuli, in sets of either 1, 2, 3 or 4 items. Once a particular set had been presented, recognition memory was tested by pairing each individual item with a novel item. Working memory capacity was measured by:

seeing how many objects the babies recognised as novel. For example, if a baby had been shown a set of 4 items, but only seemed to recognise two of them in the subsequent novelty preference pairings, memory span was assumed to be 2 items

Rose et al. (2001) reported that memory span:

increased with age. When they were aged 5 and 7 months, rather few babies could hold 3 or 4 items in working memory simultaneously (only around 25% of the sample achieved this span). By 12 months, almost half of the babies had a working memory span of 3 – 4 items.

Finally, we consider evidence that young infants appear to possess a perceptual mechanism that assumes causality. This was shown by Leslie and Keeble (1987), who were interested in 6-month-old infants' understanding of launching events. In a typical experiment, infants were shown one of two films. [blank] While the first launching event gave an impression of causality to watching adults, the second did not.

In one film, a red block moved towards a green block and then collided with it, directly setting the green block in motion. In the other film, the red block again moved towards a green block and made contact with it, but the green block only began to move after a delay of 0.5 seconds.

Following habituation to one of the films, the infants were then shown the same film in reverse. Although the change in the spatio-temporal relations in the films was the same for both groups, the reversal of the 'direct launching' film resulted in a novel causal event (green launches red). [blank] Recent adult studies using this paradigm suggest that low-level aspects of the visual system automatically foreground causal perceptual information for the brain – so this may also happen for infants (Moors et al., 2017)

The infants showed more dishabituation here (green launches red) than the infants in the delayed launching condition. Leslie (1994) argued that this showed recognition of a change in the mechanical (i.e., causal) roles of the two billiard balls. The 'pusher' was now the 'pushed'.

Social-cognitive development is broadly the development of [blank] – infants’ ability to understand that other people have unobservable entities called minds

naïve psychology

[blank] appears to be a crucial aspect of the development of social cognition and contingency detection can be observed from birth (see Lecture 2). One reason that infants may develop psychological understanding relatively early in life is that their caretakers treat them as social partners.

Contingency learning

When caring for infants, adults usually make their behaviour contingent upon, rather than ignoring of, infant attempts to communicate. In fact, caretakers may treat their infants as acting communicatively even before infants are intentionally acting in this way. Striano, Henning and Stahl (2005) explored infants’ sensitivity to social contingencies, by studying babies aged 1 and 3 months during face-to-face interactions with their mothers:

By 3 months, the infants were behaving differently in response to the different contingencies.

[blank] shows that, at some primitive level, infants are mapping the actions of other people onto the actions of their own bodies. They are also connecting the visible bodily actions of others with their own internal states. This crossmodal knowledge of what it feels like to do the act that was seen then provides a privileged access to people as special kinds of entities.

Imitation

Meltzoff suggests that the infant experiences her own internal desires (e.g., she wants her bottle) and experiences the actions (concomitant bodily movements) required to fulfil these desires or goals (she reaches for her bottle). This helps the infant to make sense of the object-directed movements of others. When another person is seen reaching for an object, the action can be imbued with [blank], because of the infant’s own experience with similar acts. Indeed, Meltzoff has produced experimental evidence that imitation is on-line from birth (e.g., Meltzoff & Moore, 1983).

goal-directedness

Another foundational mechanism for understanding psychological causation is infant [blank] behaviour. The information from another person’s eyes is very important for social cognition. For most of us, it is second nature to monitor another person’s gaze. We follow gaze in order to work out what is capturing the attention of another agent, and we look into their eyes to try and infer their emotions, their intentions and their likely future actions.

gaze monitoring

If someone deliberately avoids or prevents eye contact, it makes us feel uncomfortable. Babies, too, feel uncomfortable when another person stolidly refuses to meet their gaze. This is known as [blank] (see for example Toda & Fogel, 1993).

the “still face” paradigm, in which mothers adopt a “still face” during a playful face-to-face interaction, suspending inter-personal contingency

Gaze following and gaze monitoring behaviour has been studied in order to find out how early in development babies begin to use the gaze of another as a clue to internal mental states. Early work by Scaife and Bruner (1975) demonstrated gaze following as young as 2 months of age. However, it has been argued that acts like gaze following could be the result of conditioned learning. For example, [blank] (see Moore & Corkum, 1994, for this type of analysis).

infants could learn that when an adult turns their head, something interesting is likely to be occurring at the location that they are now gazing at

However, if gaze following is a kind of conditioned learning based on adult head turning, then infants should [blank]. Brooks and Meltzoff (2005) showed that this was not the case. Infants were selective in their gaze following behaviour.

still follow the gaze of an adult who turns their head when their eyes are closed

Another way of using gaze to understand the internal mental states of others is via [blank]. This refers to appraising a current situation on the basis of the emotional expressions and behaviours of others and then regulating your own behaviour accordingly. The infant modulates his or her reaction to an object or event by reference to information gained from the actions of another.

social referencing

One possibility is that infants modulate their behaviour because of a mentalistic interpretation of the reaction of another. For example, they may have an interpretation like “she is reacting like that because she is scared, this is a potentially dangerous toy”. A second possibility is that they modulate their behaviour simply because the emotional display acts as a signal, telling them what to do (for example, “that expression means that I should stop”). Clearly, only the former possibility implies understanding of the internal mental states of another agent. The classic study on social referencing used an apparatus called the visual cliff (Gibson & Walk, 1960). Babies of crawling age (around 9 months) would not crawl over the edge of the “cliff”, even though the solid transparent surface enabled them to do so. Later work showed that crawling behaviour on the visual cliff could be modulated by the emotional expression of the mother. One study found that:

when the mother made a fearful face, no infants crossed the cliff. When the mother made a happy face, the majority of infants crossed the drop. More recent studies have investigated how long infants take to cross the drop (Vaish & Striano, 2004).

For example, pointing is an infant behaviour that is very important. There are two kinds of pointing:

“protodeclarative” pointing and “protoimperative” pointing.

When a point has a protoimperative function, it is used to obtain an object. The infant points in order to communicate “I want that” or “Get me that”. Protoimperative pointing:

does not necessitate an understanding of the mental states of others. The infant could simply be pointing because the usual outcome is getting the desired object (this would be stimulus-response or instrumental learning).

When a point has a protodeclarative function, the point is used to “remark on” the world to another person. This is thought to involve a higher, more mentalistic level of communication: the infant appears to want to influence the mental state of another person or to share a mental state with another person. The infant is communicating something along the lines of “Look over there!” In protodeclarative pointing, the infant’s goal is [blank], an important indicator of early mindreading skills.

shared or joint attention

Simon Baron Cohen has argued that proto-declarative pointing is an early indication of a [blank] (ToM, Baron-Cohen, 1989). The use of protodeclarative pointing suggests that the infant knows about “thinking”, and is aware that another person may be thinking about something else.

“theory of mind”

There has been some debate over whether protodeclarative points are intentionally communicative acts. The pointing infant usually also alternates her gaze between the adult’s face and the object being pointed at, suggesting a desire to affect the adult’s behaviour. Liszkowski et al. (2004) provided experimental evidence that this was the case. They compared what happened when adults either rewarded infants’ protodeclarative pointing with shared attention and interest, or did not. In their study, 75 12-month-old babies interacted with an adult experimenter in one of 4 conditions. Liszkowski et al. expected [blank]. Thus infant pointing behaviour has communicative intent.

more pointing and looking in the conditions when the experimenter was refusing to share her attention with the infant, and this was essentially what they found

This was first noticed by Michotte (1963), who suggested that simple motion cues may provide the foundation for physical causal understanding and for social cognition. Adults who are shown simple displays of moving geometric shapes will describe the displays as animate (“it’s trying to get over there”). Infants also seem to:

assume animacy from certain kinds of motion.

They termed this the "intentional stance". Gergely, Nadasdy, Csibra, and Biro (1995) showed that 12-month-old infants appeared to adopt an intentional stance when analysing a simple spatial set-up involving circles and rectangles. Their experiment was based on the movements of the circles on a computer screen. When the movements could be interpreted rationally, the infants appeared to:

apply an "intentional stance" to these movements. In other words, the infants were attributing a mental cause for the apparently goal-directed behaviour that they observed.

Some aspects of mental state understanding must be purely representational, however, and not correlated with events in the real world of the here and now. An example is understanding [blank]

false belief.

In fact, the philosopher Dennett has argued that successful reasoning about false beliefs is the only convincing evidence for the attribution of mental states to others (Dennett, 1978). This is because a person who acts on the basis of a false belief acts in a way that:

would not be predicted by the real situation in the world

One of the most frequently-used methods to probe children’s understanding of false belief involves hiding an object at a location. Then, [blank]. Consequently, when the protagonist returns and seeks the object, the rational act is to look in the location at which the protagonist believes the object to be hidden. But this belief of the protagonist is now false – the object is now in a new location. Hence in order to find the object, the protagonist must discover this new location. However, the protagonist will first seek the object at the wrong location. Knowledge of this likely action sequence is thought to provide an index of the ability to understand false beliefs.

while the protagonist is absent, the hiding place is changed

Onishi and Baillargeon (2005) devised a way of testing false belief understanding in 15 month-old infants, using the violation-of-expectation paradigm and a search task. During familiarisation trials, infants watched as a protagonist hid a toy in one of two possible locations (a yellow box or a green box). The openings of the boxes were at 90’ to the infants, 20 February 2025 so that the infants could not see into the boxes, and were concealed by fringing. In the first familiarisation trial, the actor put the toy into the green box. In the next two familiarisation trials, she put her hand into the green box as though to grasp the toy, and rested her hand there. The infants then saw a belief induction trial. In the false belief condition, they watched as the toy moved location into the yellow box out of view of the actor. The infants observed that the actor did not see this move. In the true belief condition, the actor and infant both watched as the toy moved location. A test trial was then given, during which the actor simply placed her hand into one of the boxes:

In the false belief condition, infants were expected to look longer when this was the yellow box, as the actor believed that the toy was in the green box. In the true belief condition, infants were expected to look longer when this was the green box, as the actor believed that the toy was in the yellow box. Further conditions checked the analogous predictions when the first hiding place was the yellow box. Onishi and Baillargeon found that the infants indeed looked significantly longer when the box that the actor chose to search was inconsistent with her belief about the toy’s location.

Finally, we consider other demonstrations that infants attribute mental causes for the goal directed behaviour that they observe in other agents. Work from Tomasello and his colleagues demonstrates that infants:

take context into account when inferring the reason for goal-directed behaviour. For example, they show differential imitation of the same action because of changes in context (whether a mouse is hopping home to his house or not).

Infants also imitate the acts of others differentially depending on whether they perceive these acts to be intentional or accidental. They appear to:

interpret an adult’s behaviour as intentional, and screen out the accidental and unintended actions. Note that the ability to recognise intentional actions provides a powerful boost to the infant’s capacity for imitative learning. An infant who selectively imitates only the intentional acts of others will acquire many significant cultural skills.

Finally, infants differentiate between adults who are [blank] (Behne et al., 2005). Again, this suggests a capacity for an understanding of psychological causation.

unwilling to carry out an act desired by the infant versus unable to carry out this act

Traditionally, language acquisition was studied:

separately from cognitive development. The acquisition of language was considered such a remarkable feat for the infant brain that it was concluded that a special capacity must be at work. Linguistic capacities were thought to be distinct from the capacities underpinning broader cognitive development.

Yet language enables [blank], and so some of the factors that support successful language acquisition must overlap with some of the factors underpinning social cognitive development.

communication

For cognitive development per se, language also has a crucial intra-psychological function, namely that it is [blank]. In this sense (see Vygotsky, Lecture 1), language provides a psychological tool for organising and changing our own cognitive experiences. Language enables us to think about what we know, to plan and to problem solve, and to change our own understandings of our experiences: all inside our own heads.

symbolic. Words are symbols that encode our experiences and that stand for concepts and events in the everyday world

In order to acquire a spoken language, the brain has to learn to perceive the patterns of sound combinations that constitute words. The brain also has to learn the individual sound elements that comprise particular words in a given language – and there are over 6000 world languages. This process is called:

phonological development.

[blank] is the inventory of the sound system of a language, comprising knowledge of the sounds themselves and the specific patterns or regularities by which sounds in words can be organised.

Phonology

The mechanisms that the brain uses for phonological learning appear to be general cognitive mechanisms like:

statistical learning and imitation

Social interaction is also important for phonological learning, as is [blank] (Lecture 3).

face-to-face contingent interaction

As spoken language is a sound signal, there are also some special mechanisms of acoustic learning. Human language also has a unique teaching mechanism, called:

infant directed speech (IDS) or “Parentese”, which has a special exaggerated prosodic register. IDS is found across cultures, genders and ages.

Because speakers are different from each other, there is high variability in the speech signal as an acoustic signal. A word like “bat” spoken by an adult male will be physically different from the same word spoken by a five-year-old girl. Linguistics gets round some of these differences by calling the individual sound elements that make up words in a language:

“phonemes”

Phonemes are an abstraction from the physical acoustic stimulus, and are defined in terms of [blank]. A word like “bat” differs from a word like “pat” by a single phoneme, /b/ versus /p/.

changing meaning

In order to produce these two stop consonants, we [blank]. At a certain point, when someone is producing these sounds, we stop hearing the phoneme /b/ and begin hearing the phoneme /p/.

vibrate our vocal chords and then obstruct the air flow of the sound that we make using the lips

For adults, the point at which you stop hearing a /b/ and you begin hearing a /p/ sound is very abrupt, hence this is called:

categorical perception. An important early question was when the infant brain acquired categorical perception.

The classic study was done by Eimas and his colleagues in 1971, using dishabituation of sucking. They created a physical continuum from /b/ to /p/ in which voice onset time incremented in 20 ms steps. For adult listeners, the category boundary was between 20 ms and 40 ms. Hence when a stimulus with a voice onset time of 20 ms was compared to one with a voice onset time of 40 ms, the perceptual experience changed from /b/ to /p/. However if a stimulus with a voice onset time of 0 ms was compared to one with an onset time of 20 ms, this was perceived by adults as the same perceptual event, namely /b/. Remarkably:

infants showed exactly the same categorical perception, even as young as one-month old

Given that the infant is born without any knowledge of which language they will be expected to acquire, [blank]. This appears to be what happens during the first year of life.

the brain needs to be sensitive to all possible phonetic discriminations that might be needed. Categorical boundaries that are not needed for a particular language could then be discarded

Again using sucking paradigms, it has been shown that whereas young infants (below around 6 - 9 months in age) are still sensitive to [blank], as shown in the study by Werker and Tees (1984).

phoneme divisions that are not used in their language, by around a year this sensitivity has disappeared

Part of the perceptual learning underlying this change is the “magnet effect”. [blank] The magnet effect reflects experience with your specific native language/s. Meanwhile, listening to speech activates similar brain regions in infants and adults.

Infants learn the acoustic features that typically occur together, and construct a prototypical phoneme, eg a prototypical /b/. Non-prototypical sounds will then be perceived as more similar to the category prototype than they are to each other, even though the actual physical difference between the stimuli may be equal.

The involvement of social interactions with live humans seems to be of critical importance for phonetic learning. This was demonstrated in a study comparing English and Mandarin. Pat Kuhl had native Mandarin Chinese-speaking graduate students play with 9-month-old American babies, and videoed all the interactions. The students played with the babies with toys and books in a natural manner, but always speaking in Mandarin:

Whereas a one-year old American baby should no longer hear speech contrasts used in Mandarin Chinese, the babies in Kuhl’s study continued to maintain these phonetic distinctions

Kuhl also manipulated whether the babies participated in live play sessions, or whether they watched videos of the play sessions. The “video babies” received identical acoustic exposure to Mandarin Chinese, but not in a live setting. Kuhl found that:

only babies who experienced live face-to-face interaction retained the Mandarin Chinese speech contrasts.

Although phonological development is crucial for language acquisition, the primary function of language is communication. Infants need to learn what words mean, so that they can be equal partners in linguistic interactions: [blank’. This requires them to make mappings between sound patterns and specific concepts and events in the everyday world. Concepts are pre-linguistic, in that infants understand a lot about the kinds of things that are in the world and about the kinds of events and actions that are named by language long before they can speak.

semantic development

Nevertheless, learning words also changes children’s concepts. Languages differ in how they encode experience, and therefore conceptual development will reflect these language differences. Parentese or IDS also helps children to learn mappings between words and their referents. For example, Fernald showed that mothers unconsciously:

emphasise novel words when they are reading stories to their infants. When reading another adult the same story, the mothers did not place extra emphasis on these particular words.

Given their limited language abilities in the first two years of life, most children go through a phase of ‘overextension’. Overextension is:

using a single word to apply to many different referents, such as using ‘ball’ to name apples, grapes, bell clappers, and also balls.

Again, this language-universal phenomenon was originally thought to show limited conceptual abilities on the part of children. For example, it seemed possible that a child who called an apple ‘a ball’ was unable to distinguish apples from balls. Systematic experimental work showed this idea to be wrong:

Children never overextend in language comprehension, only in production.

Overextension is a by-product of stretching a limited vocabulary to communicate as flexibly as possible during the one-word stage. In fact, [blank]. Young children first talk about salient objects and events in their day-to-day lives: family members, pets, words connected to routines like meals and bedtime, and words referring to the movement of people and objects.

the first words that are typically used by young children are very similar across languages and cultures

Learning word-object relations is supported for infants by other adult behaviours. For example, adults spend a lot of time naming things for infants, and usually they combine naming with pointing to the novel referent. Babies learn this connection, and accordingly:

they give greater attention to objects that are both pointed to and labelled