Infant cognitive development

Infant cognitive development is the first stage of human cognitive development, in the youngest children. The academic field of infant cognitive development studies of how psychological processes involved in thinking and knowing develop in young children.^[1] Information is acquired in a number of ways including through sight, sound, touch, taste, smell and language, all of which require processing by our cognitive system.^[2] However, cognition begins through social bonds between children and caregivers, which gradually increase through the essential motive force of Shared intentionality.^[3] The notion of Shared intentionality describes unaware processes during social learning at the onset of life when organisms in the simple reflexes substage of the sensorimotor stage of cognitive development do not maintain communication via the sensory system.^[3]

Scientific investigation in this field has its origin in the first half of the 20th century, an early and influential theory in this field is Jean Piaget's theory of cognitive development. Since Piaget's contribution to the field, infant cognitive development and methods for its investigation have advanced considerably, with numerous psychologists investigating different areas of cognitive development including memory, language and perception, coming up with various theories^[4]—for example Neo-Piagetian theories of cognitive development.

Overview

Main article: Nature versus nurture

Tabula rasa is an idea (by now a discredited theory) that, at birth, the human mind is a "blank slate" without any rules for processing data, that data is added and rules for processing it are formed solely by one's sensory experiences. The modern idea of the theory is mostly attributed to John Locke's An Essay Concerning Human Understanding, written in the 17th century.

Its corollary, nativism, argues that we are born with certain cognitive modules that allow us to learn and acquire certain skills, such as language, (for example the theory of Universal Grammar, the theory that the 'programming' for grammar is hardwired in the brain) and is most associated with the recent work of Noam Chomsky, Jerry Fodor, and Steven Pinker.

If one accepts that nothing is known until learned, and that everyone shares a basic common sense, it appears infants must—to some degree—make some specific ontological inferences about how the world works, and what kinds of things it contains. This procedure is studied in psychology and its validity is studied in philosophy.

We acquire these ordinary [common sense] beliefs at an early age and we take them for granted in everyday life; ... Then, because we are also self-reflective creatures, we turn back on our commonsense assumptions and find them to be more puzzling and problematic than we had bargained for. The concepts we habitually employ raise the kinds of disturbing questions we call philosophical'.

— Colin McGinn, Problems in Philosophy. 1993, ^[5]

The notion of Shared intentionality proposes another approach to the problem. Based on recent insights in neuroscience research, it is argued that this collaborative interaction emerges in the mother-child pairs at birth for sharing the essential sensory stimulus of the actual cognitive problem.^[6][7]

Jean Piaget

Through observations of children, Jean Piaget established a theory of cognitive development. According to Piaget's theory of cognitive development there are four stages of cognitive development.^[8][9]

1. Sensorimotor Stage (Birth to 24 Months)
2. Preoperational Stage (24 Months to 7 Years)
3. Concrete Operational Stage (7 Years to 12 Years)
4. Formal Operational Stage (12 Years and Up)

Infant cognitive development occurs in the Sensorimotor stage which starts at birth and extends until the infant is about 2 years of age. The sensorimotor stage is made up of six sub-stages.

Stage	Age
Stage 1 – Reflexes	Birth to 6 weeks
Stage 2 – Primary Circular Reactions	6 weeks to 4 months
Stage 3 – Secondary Circular Reactions	4 months to 8 months
Stage 4 – Coordination of Secondary Circular Reactions	8 months to 12 months
Stage 5 – Tertiary Circular Reactions	12 months to 18 months
Stage 6 – Mental Representation	18 months to 24 months

Lev Vygotsky

Lev Vygotsky was also very influential in cognitive development theory. His theory included the Zone of proximal development.^[10] Vygotsky also believed that social and cultural factors contributed heavily to cognitive development.^[11] Vygotsky argued that development first takes place socially as infants observe their parent's behaviour and try to imitate it. As this imitation occurs, parents will guide their children, correcting them and provide challenges for them. Play is an integral part of cognitive development according to Vygotsky, as it is through this play that children gain confidence in their language skills, and start regulating their own thought processes. Through his research Vygotsky suggested that a child's performance differs depending on whether they are solving a problem alone or if another child or adult is assisting them. He refers to this difference as the "zone of proximal development". The theory goes that if a child is learning to complete a task, and a more competent person is able to provide assistance, then the child is able to move into a new zone of development and problem solving. Vygotsky refers to this movement through assistance as "scaffolding" and helps bridge the gap between the child's current cognitive abilities and their full potential.^[12]

Erik Erikson

Erik Erikson was a prominent developmental psychologist, who produced a psychoanalytical theory of psychosocial behaviour, showing 8 stages of development from infancy to adulthood. At each stage the individual is set with a potential conflict, and either success or failure at each point will go on to determine the outcome of the psychological state of the person. The first stage of development runs from birth to 18 months and thus covers the infancy period. The conflict which Erikson identified during this time was trust vs mistrust. During this vulnerable point in the child's life, they are faced with uncertainties in the world and are therefore reliant on their caregiver. If the child receives consistent care then Erikson claimed that the infant would develop a sense of trust. However, if the care received has been unreliable then mistrust will develop, which may result in heightened feelings of insecurity and anxiety, in future relationships.^[13]

The development of mental processes

Adaptive nature of cognitive immaturity

Development is typically considered to be something progressive: as we age we move from more simple to more complex structures or behaviours. This causes us to interpret early or immature forms of cognition as incomplete forms of the adult model. This does not always hold true. Immature forms of development can serve some function of their own, as it adapts for the current environment of the infant. For example, infant's relatively poor perceptual skills protect their nervous system from undergoing sensory overload. The fact that infants have slow information processing prevents them from establishing intellectual habits early in their lives that would cause problems later in life, as their environments are significantly different. From this it could be argued that infants and young children's cognitive and perceptual abilities might be designed to be suited to their needs at that particular time in their lives rather than incomplete versions of the more sophisticated models possessed in adults. Hanus Papousek (1977) looked at the concept that learning at an early stage of development may not be beneficial to the infant if it creates overstimulation. In an experiment he conditioned infants to turn their heads to the sound of a buzzer. The training for the task began either at birth or at 31 or at 44 days. He discovered that infants took many more trials and days to learn the task if they learned from birth than the infants who learned later. Infants need stimulation, but if stimulation is too great than it could distract infants and young children from other tasks, and replace other, more crucial activities to their development such as social interaction.^[14]

Attention

Main article: Attention

According to Professor Wilhelm Wundt (1832-1920), physiologist and philosopher, attention is the concentration of awareness on some phenomenon during a period, which is necessary to elevate the clear perception of the narrow region of the content of consciousness and which is feasible to control this focus in mind.^[15] Therefore, attention is a process of controlling thought that continues over time.^[16] His experiments showed that the size of the focal area of consciousness in adults ranges from three to six items.^[15] According to associate professor at Rīga Stradiņš University Sandra Mihailova and research professor in bioengineering at Liepaja University Igor Val Danilov, the development of the scope of attention in young children becomes evident within the first three years of life as they show considerable advances in increasing focal area.^[17] The empirical data has four stages:

• The first stage, with up to two items in the focal point, lasts up to about six months of age.^[17][18]
• The second stage, with up to three items, begins after eight months.^[17][19]
• The third stage appears at about 3.5 years of age with four items.^[17][20]
• The fourth stage starts in children when they are about five years old and can hold five or more items in the focal point.^[17][19]

Memory

Main article: Memory development

The development of memory in children becomes evident within the first 2 to 3 years of a child's life as they show considerable advances in declarative memory. This enhancement continues into adolescence with major developments in short term memory, working memory, long-term memory and autobiographical memory.^[21]

Research on the development of memory has indicated that declarative, or explicit memory, may exist in infants who are even younger than two years old. For example, newborns who are less than 3 days old demonstrate a preference for their mother’s own voice.^[22]

Perception

Attribution of causality

The perception of causality was initially studied by professor Albert Michotte where he presented adults with animated images of moving balls.^[23] By manipulating the direction and timing of the moving balls (spatial and temporal dimensions) he was able to influence participants’ perception of causality. There is contradicting evidence on whether causal perception is innate and present at birth or whether it is a result of perception development. Through research with very young infants, many studies have shown support for the theory that humans are born with the mechanisms needed for the perception of causality.^[24][25][26] Recent research has even shown this ability in newborns only a few hours old.^[27] However, other studies have shown similar results received by Michotte (1976) in infants as young as 6 months, but not younger.^[28][29] These studies support a more developmental progression of abilities required for the perception of causality.

Object permanence

Object permanence is the understanding that an object continues to exist, even when one cannot see it or touch it. It is an important milestone in the stages of cognitive development for infants. Numerous tests regarding it have been done, usually involving a toy and a crude barrier which is placed in front of the toy, and then removed repeatedly (peekaboo). In early sensorimotor stages, the infant is completely unable to comprehend object permanence. Psychologist Jean Piaget conducted experiments with infants which led him to conclude that this awareness was typically achieved at eight to nine months of age. Infants before this age are too young to understand object permanence, which explains why infants at this age do not cry when their mothers are gone – "Out of sight, out of mind". A lack of object permanence can lead to A-not-B errors, where children look for an object at the location where they first discovered it rather than where they have just seen it placed.

Depth perception

Studies in psychology^[30] also suggest that three dimensionality and depth perception is not necessarily fully intuitive, and must be partially learned in infancy using an unconscious inference. The acquisition of depth perception and its development in infant cognitive systems was researched by professor Richard D. Walk. Walk found that human infants can discriminate depth well from an "innate learned" point of view: they are able to discriminate depth from the age at which they can be tested. However, their visual mechanisms are still maturing. Walk discovered that infants are better able to discriminate depth when there is a definitive pattern separating the deeper and shallower areas than if either one is at all indefinite, and that the depth and distance must be of a certain level of distance in order to be successfully distinguished by the infant. According to Walk there is a clear development of perceptual behaviour, as with increasing age it is shown that children are able to discriminate between depths more accurately, and gauge more subtle differences between depths.^[31]

Physical laws

Largely thanks to the innovative strategies developed by professor Renee Baillargeon and her colleagues, significant insights have been developed regarding how young infants comprehend natural physical laws. Much of this research depends on carefully observing when infants react as if events are unexpected. For example, if an infant sees an object that appears to be suspended in mid-air, and behaves as if this is unexpected, then this suggests that the infant has an understanding that things usually fall if they are not supported. Baillargeon and her colleagues have contributed evidence, for example, about infants’ understanding of object permanence^[32] and their reasoning about hidden objects.^[33]

Shared intentionality

The noted above hypotheses plausibly explain perception development when the nervous system of the young organism has already mastered the mode to distinguish relevant stimuli from the cacophony of electromagnetic waves, chemical interactions, and pressure fluctuations. The Shared intentionality approach attempts to describe environmental learning in the previous developmental period (even before birth) when nothing is still known, and the young organism just learns how to assimilate basic common meanings.^[6] It still needs to overcome the binding problem to choose relevant stimuli for primary data entry. Neuroscience research studies ^{[34][35][36][37][38][39]} declared observed inter-brain activity under conditions without communication in pairs while subjects were solving the shared cognitive problem, and they registered an increased inter-brain activity in contrast to the condition when subjects solved a similar problem alone. These data show that collaborative interaction without sensory cues can emerge in mother-child dyads, providing Shared intentionality, which indicates to the immature organism the essential sensory stimulus of the actual cognitive problem.^[6] Latvian professor Igor Val Danilov proposed the Shared intentionality hypothesis, which attempts to explain neurophysiological processes at the beginning of cognitive development at different levels of interaction, from interpersonal dynamics to neuronal interactions.^[40][41]

Language

Main article: Language acquisition

From birth, babies are learning to communicate. The communication begins with crying and then begins to develop into cooing and babbling. Infants develop their speech by mimicking those around them. Gestures and facial expressions are all part of language development. In the first three months of life babies will generally use different crying types to express their different needs, as well as making other sounds such as cooing. They will begin mimicking facial expressions and smiling at the sight of familiar faces. Between the ages of 4–6 months infants have a greater response towards different tones in voices, and greater engagement, watching the speaker's face. The child's own language skills develop with larger variation in babbling sounds, and elicit responses in conversation through babbling. From 7 months to the end of their first year babies are able to understand frequently heard words and can respond to simple requests. Their babbling becomes more complex and they communicate with it as if they are making sense, they use babbling to express their desires. Non-verbal communication also develops and actions such as waving goodbye are produced. This is also the period in which babies often say their first word, an important milestone in the child's life.^[42]

Metacognition

Main article: Metacognition

Self-awareness

The most common technique used in research for testing self-awareness in infants is a mirror test known as the "Rouge Test".^[43][44] The rouge test works by applying a dot on an infant’s face and then placing them in front of the mirror. If the infant investigates the dot on their nose by touching it, they are thought to realize their own existence and have achieved self-awareness. A number of research studies have used this technique and shown self-awareness to develop between 15 and 24 months of age.^[45][46] Some researchers take language such as "I, me, my, etc." as an indicator of self-awareness.^[47]

Rochat (2003) described a more in-depth developmental path in acquiring self-awareness through various stages.^[48][49] He described self-awareness as occurring in 5 stages beginning from birth.

Stage	Description
Stage 1 – Differentiation (from birth)	Right from birth infants are able to differentiate the self from the non-self. A study using the infant rooting reflex found that infants rooted significantly less from self-stimulation, contrary to when the stimulation came from the experimenter.[50]
Stage 2 – Situation (by 2 months)	In addition to differentiation, infants at this stage can also situate themselves in relation to a model. In one experiment infants were able to imitate tongue orientation from an adult model.[51] Additionally, another sign of the differentiation is when infants bring themselves into contact with objects by reaching for them.[52]
Stage 3 – Identification (by 2 years)	At this stage the more common definition of "self-awareness" comes into play, where infants can identify themselves in a mirror through the "rouge test" as well as begin to use language to refer to themselves.
Stage 4 – Permanence	This stage occurs after infancy when children are aware that their sense of self continues to exist across both time and space.
Stage 5 – Self-consciousness or meta-self-awareness	This also occurs after infancy. This is the final stage when children can see themselves in 3rd person, or how they are perceived by others.

Symbolic thought

Symbolic thought refers to the ability to use words, images, and other symbols to represent words or feelings. During the preoperational stage a child's capacity for symbolism increases, this is shown by their increase in language use during this stage. This can also be seen by the way children play with objects, a stick becomes a sword and a box becomes armor. Children in this stage still might not understand that a map represents a real place, and that a picture of food does not have a smell.^[53]

Notes

• ^ The Structures of the Common-Sense World
• ^ Evolutionary Psychology: A Primer Archived February 6, 2023, at the Wayback Machine

References

1. Oakly, L. (2004). Cognitive Development. New York: Routledge.
2. Esgate, A.; Groome, D.; Baker, K.; Heathcote, D.; Kemp, R.; Maguire, M.; Reed, C. (2005). Introduction to applied cognitive psychology. New York, NY: Psychology Press.
3. Tomasello, M. (2019). "Becoming human: A theory of ontogeny." Cambridge, Massachusetts, USA: Harvard University Press.
4. Bremner, JG (1994). Infancy (2 ed.). Blackwell. ISBN 978-0-631-18466-9.
5. McGinn, Colin (1993). Problems in Philosophy, The Limits of Inquiry. Blackwell Publishing. p. 8. ISBN 978-1557864758.
6. Val Danilov, Igor (2023). "Low-Frequency Oscillations for Nonlocal Neuronal Coupling in Shared Intentionality Before and After Birth: Toward the Origin of Perception". OBM Neurobiology. 7 (4): 1–17. doi:10.21926/obm.neurobiol.2304192.
7. Val Danilov, Igor; Mihailova, Sandra (2022). "A New Perspective on Assessing Cognition in Children through Estimating Shared Intentionality". Journal of Intelligence. 10 (2): 21. doi:10.3390/jintelligence10020021. ISSN 2079-3200. PMC 9036231. PMID 35466234.
8. Piaget, J.; Inhelder, B. (1969). The psychology of the child. Basic Books.
9. Piaget, J. (1970). "Piaget's theory". In Mussen, P. (ed.). Handbook of child psychology. Vol. 1. New York: Wiley.
10. Vygotsky, L. S. (1978). Mind in society: The development of higher psychological processes. Cambridge, Massachusetts: Harvard University Press.
11. Harré, Rom (2006). Key thinkers in psychology (Repr. ed.). London [u.a.]: Sage Publ. ISBN 9781412903448.
12. "Lev Vygotsky's Cognitive Development Theory and the Benefits of Play". Archived from the original on February 27, 2018. Retrieved March 30, 2017.
13. Sigelman, Carol. K, Rider, Elizabeth. A, 2012, Life-Span Human Development, Cengage Learning
14. Bjorklund, F., Causey, Kayla B., 2012, Children's Thinking" Cognitive Development and Individual Differences, SAGE Publications
15. Wilhelm Wundt. (1912). Introduction to Psychology, trans. Rudolf Pintner (London: Allen, 1912; reprint ed., New York: Arno Press, 1973)
16. Leahey, T.H. (1979). "Something old, something new: Attention in Wundt and modern cognitive psychology." Journal of the History of the Behavioral Sciences, 15(3), 242-252.
17. Val Danilov, I.; Mihailova, S. (2022). "A Case Study on the Development of Math Competence in an Eight-year-old Child with Dyscalculia: Shared Intentionality in Human- Computer Interaction for Online Treatment Via Subitizing." OBM Neurobiology; 6(2): 122; doi:10.21926/obm.neurobiol.2202122.
18. Starkey, P.; Cooper, R.G.Jr. (1980). "Perception of numbers by human infants." Science.; 210: 1033-1035.
19. Starkey, P.; Cooper, R.G. (1995). "The development of subitizing in young children." Br J Dev Psychol.; 13: 399-420.
20. Gray, S.A.; Reeve, R.A. (2014). "Preschoolers’ dot enumeration abilities are markers of their arithmetic competence." PLoS ONE.; 9: e94428.
21. Siegler, R. S. (1998). Children's Thinking (3rd ed.). Upper Saddle River, NJ: Prentice Hall. ISBN 978-0-13-397910-7.
22. DeCasper, A.J.; Fifer, W.P. (1980). "Of human bonding: Newborns prefer their mothers' voices". Science. 208 (4448): 1174–1176. Bibcode:1980Sci...208.1174D. CiteSeerX 10.1.1.553.1738. doi:10.1126/science.7375928. PMID 7375928.
23. Michotte, A. (1967). The Perception of Causality. New York, NY: Basic Books.
24. Leslie, A. M. (1982). "The perception of causality in infants". Perception. 11 (2): 173–186. doi:10.1068/p110173. PMID 7155770. S2CID 2901777.
25. Leslie, A. M. (1984). "Spatiotemporal continuity and the perception of causality in infants". Perception. 13 (3): 287–305. doi:10.1068/p130287. PMID 6514514. S2CID 21381509.
26. Saxe, R.; Carey, S. (2006). "The perception of causality in infancy". Acta Psychologica. 123 (1–2): 144–165. doi:10.1016/j.actpsy.2006.05.005. hdl:11858/00-001M-0000-0012-8F4E-B. PMID 16905110.
27. Mascalzoni, E.; Regolin, L.; Vallortigara, G.; Simion, F. (2013). "The cradle of causal reasoning: newborns' preference for physical causality". Developmental Science. 16 (3): 327–335. doi:10.1111/desc.12018. PMID 23587033.
28. Cohen, L. B.; Amsel, G. (1998). "Precursors to infants' perception of the causality of a simple event". Infant Behavior & Development. 21 (4): 713–731. doi:10.1016/s0163-6383(98)90040-6.
29. Oakes, L. M. (1994). "Development of infants' use of continuity cues in their perception of causality". Developmental Psychology. 30 (6): 869–879. doi:10.1037/0012-1649.30.6.869.
30. "The 'Visual Cliff'". Library for Psychology in the New Millennium. Archived from the original on April 6, 2019. Retrieved September 26, 2016.
31. Walk, Richard D., 1966, The Development of Depth Perception in Animals and Human Infants, Wiley
32. Baillargeon, R.; DeVos, J. (1991). "Object permanence in young infants: Further evidence". Child Development. 62 (6): 1227–1246. doi:10.2307/1130803. JSTOR 1130803. PMID 1786712.
33. Baillargeon, R (2004). "Infants' reasoning about hidden objects: Evidence for event-general and event-specific expectations". Developmental Science. 7 (4): 391–424. doi:10.1111/j.1467-7687.2004.00357.x. PMC 4215973. PMID 15484586.
34. Liu, J., Zhang, R., Xie, E. et al. (2023). "Shared intentionality modulates interpersonal neural synchronization at the establishment of communication system." Commun Biol 6, 832 (2023). https://doi.org/10.1038/s42003-023-05197-z
35. Painter, D.R., Kim, J.J., Renton, A.I., Mattingley, J.B. (2021). "Joint control of visually guided actions involves concordant increases in behavioural and neural coupling." Commun Biol. 2021; 4: 816.
36. Hu, Y., Pan, Y., Shi, X., Cai, Q., Li, X., Cheng, X. (2018). "Inter-brain synchrony and cooperation context in interactive decision making." Biol Psychol. 2018; 133: 54-62.
37. Fishburn, F.A., Murty, V.P., Hlutkowsky, C.O., MacGillivray, C.E., Bemis, L.M., Murphy, M.E., et al. (2018). "Putting our heads together: Interpersonal neural synchronization as a biological mechanism for shared intentionality." Soc Cogn Affect Neurosci. 2018; 13: 841-849.
38. Szymanski, C., Pesquita, A., Brennan, A.A., Perdikis, D., Enns, J.T., Brick, T.R., et al. (2017). "Teams on the same wavelength perform better: Inter-brain phase synchronization constitutes a neural substrate for social facilitation." Neuroimage. 2017; 152: 425-436.
39. Astolfi, L., Toppi, J., De Vico Fallani, F., Vecchiato, G., Salinari, S., Mattia, D., et al. (2010). "Neuroelectrical hyperscanning measures simultaneous brain activity in humans." Brain Topogr. 2010; 23: 243-256.
40. Val Danilov, I. (2023). "Theoretical Grounds of Shared Intentionality for Neuroscience in Developing Bioengineering Systems." OBM Neurobiology 2023; 7(1): 156; doi:10.21926/obm.neurobiol.2301156
41. Val Danilov, Igor (2023). "Shared Intentionality Modulation at the Cell Level: Low-Frequency Oscillations for Temporal Coordination in Bioengineering Systems". OBM Neurobiology. 7 (4): 1–17. doi:10.21926/obm.neurobiol.2304185.
42. Kim, Yaebin, Byington, Teresea, 2015, Infant Language Development, University of Nevada Cooperative Extension
43. Amsterdam, B. (1972). "Mirror self-image reactions before age two". Developmental Psychology. 5 (4): 297–305. doi:10.1002/dev.420050403. PMID 4679817.
44. Gallup, G. G. (1970). "Chimpanzees: Self-recognition". Science. 167 (3914): 86–87. Bibcode:1970Sci...167...86G. doi:10.1126/science.167.3914.86. PMID 4982211. S2CID 145295899.
45. Lewis, M.; Brooks-Gunn, J. (1979). Social cognition and the acquisition of self. New York, NY: Plenum Press.
46. Rochat, P.; Broesch, T.; Jayne, K. (2012). "Social awareness and early self-recognition". Consciousness and Cognition. 21 (3): 1491–1497. doi:10.1016/j.concog.2012.04.007. PMID 22673374. S2CID 16697739.
47. Bates, E. (1990). "Language about me and you: Pronominal reference and the emerging concept of self". In Cicchetti, D.; Beeghly, M. (eds.). The self in transition: Infancy to childhood. Chicago: University of Chicago Press. pp. 165–182.
48. Rochat, P. (2003). "Five levels of self-awareness as they unfold early in life". Consciousness and Cognition. 12 (4): 717–731. doi:10.1016/s1053-8100(03)00081-3. PMID 14656513. S2CID 10241157.
49. Legrain, L.; Cleeremans, A.; Destrebecqz, A. (2011). "Distinguishing three levels in explicit self-awareness" (PDF). Consciousness and Cognition. 20 (3): 578–585. doi:10.1016/j.concog.2010.10.010. PMID 21093301. S2CID 18739652.
50. Rochat, P.; Hespos, S. J. (1997). "Differential rooting response by neonates: evidence for an early sense of self". Early Development and Parenting. 6 (2): 150.1–150.8. doi:10.1002/(sici)1099-0917(199709/12)6:3/4<105::aid-edp150>3.0.co;2-u.
51. Meltzoff, A. N.; Moore, M. K. (1992). "Early imitation within a functional framework: The importance of person identity, movement, and development". Infant Behavior and Development. 15 (4): 479–505. doi:10.1016/0163-6383(92)80015-m. PMC 4137790. PMID 25147415.
52. Rochat, P.; Goubet, N. (1995). "Development of sitting and reaching in 5- to 6-month-old infants". Infant Behavior and Development. 18: 53–68. doi:10.1016/0163-6383(95)90007-1.
53. Hockenbury, Don and Hockenbury, Sandra "Discovering Psychology:Fifth Edition". Worth Publishers, 2010, p. 389.

Further reading

• Bower, Tom (1977), The Perceptual World of the Child, London: Open Books, ISBN 978-0-7291-0088-5
• Bower, T.G.R. (1982), Development in Infancy (2nd ed.), San Francisco: W.H. Freeman & Co., ISBN 978-0-7167-1302-9

External links

• Infant education (audio)