An Introduction to Developmental psychology by A. Slater and G. Bremner (third edition) - Chapter 4

Prenatal development is the development of human individuals before they are born. The foetus is the organism 12 weeks after conception until birth. The embryo is the developing organism during the period when organs are forming. A neonate is an infant less than a month old. Postnatal development is the development of a human individual after he is born. It is now possible to study foetuses using ultrasound and fMRI.

The ectoderm is the outermost of three primary germ layers of an embryo. The central nervous system develops from the ectoderm. The other two layers are the endoderm and the mesoderm. The endoderm develops into the neural plate, a thickening of cells that will give rise to the brain. The neural plate folds into a neural tube, which is a hollow structure in the embryo that gives rise to the brain and spinal column. The first movements of the foetus are reflexes that occur using the spinal cord, without the use of the brain.

The cerebral cortex is the area of the brain that is associated with complex tasks, such as memory and language. In the first two or three months of pregnancy, there is relatively little development in this area. The cerebral hemispheres develop from the forebrain at about 9 weeks and rapidly increase in size and will later become highly specialised areas in the brain. After 6 months, sulci (deep narrow grooves of the outer surface of the brain) and gyri (ridges on the outer surface of the brain) have appeared. This shows that the brain has developed a lot since infolding is necessary to accommodate for the total brain area. At around 15 weeks, there is a lull in movement, because inhibition has appeared in the brain and this leads to a period of reorganisation of behaviour. After 27 weeks, the cerebral cortex is mature, but the brain continues to grow in size until adulthood, mostly because of myelination, the process by which myelin is formed around neurons. Myelin causes faster neurotransmission. Foetuses at about 24 weeks have the ability to learn and have a very basic form of memory.

Foetuses’ behaviour becomes progressively more organised as the pregnancy proceeds. At 34 weeks, they don’t continuously move but have distinct patterns of rest and activity. There are now two dominant patterns of activity: quiet sleep or active sleep. In the active sleep, the foetuses will be responsive to sensory stimuli. Early neuronal networks are being stimulated during active sleep. Foetuses at the end of pregnancy no longer spend a lot of time in active sleep, because their brain has matured and more inhibitory pathways have developed. Term foetuses are more active when the mother is not, for example, when she is asleep.

The emergence of the senses follows a set mammalian pattern of development. The rooting reflex is the reflex that causes new-borns to respond to one of their cheeks being touched by turning their heads in that direction.

  1. Touch
    This is the first sense that is developed and is shown by the rooting reflex.
  2. Chemosensory system
    This system is the second thing that is developed and included gustatory (taste) and olfactory (smell) senses. Substances such as cigarette smoke can pass into the bloodstream of the foetus. During the fourth month, foetuses begin to inhale amniotic fluids, which is the fluid surrounding the foetus. It is possible that foetuses learn some food preferences in utero. New-borns are selectively responsive to their own amniotic fluid and their own mother’s colostrum, the breast fluid that precedes true milk.
  3. Vestibular system
    This is the sensory system that contributes to balance and spatial information. Foetuses move around a lot. They are constantly subjected to passive motion. The system is actively being stimulated and this stimulation is very important for normal growth and development. Preterm infants that are deprived of the vestibular stimulation show lags in neurobehavioural development. Kangaroo Care, skin/to/skin contact between the mother and the pre/term infant favourably affects the maturation of the autonomic nervous system. This system starts to work at about 14 weeks.
  4. Visual system
    There is little visual stimulation for the developing foetus. It is barely stimulated during gestation, but it is functioning at birth. The eyes start to develop at about 5 weeks of pregnancy. The visual pathway is developed simultaneously with the eyes. At the end of the first trimester, the nerve fibres of the eyes have crossed. The striate cortex is concerned with many aspects of basic visual function. At birth, the visual system continues to develop, as it is still relatively immature.
  5. Auditory system
    This development begins at about 6 weeks of pregnancy. The cochlea forms one coil at 9 weeks. By 10 weeks, sensory cells are present in the semi-circular canals. Cochlear function is considered to begin at around 24 weeks. After this time, the foetus can begin to detect vibroacoustic stimulation. The sounds that reach the foetuses are low-frequency sounds. The uterine sound environment is rich. Very loud sounds will result in a very fast heart rate.

Transnatal learning is learning that occurs during the prenatal period which is remembered during the postnatal period. Foetuses show habituation and dishabituation, a form of learning. Foetuses can probably learn about sounds they hear in utero. Early postnatal responding is influenced by prenatal sounds. This is shown by the fact that neonates prefer a muffled version of their mother’s voice, something they would hear in the womb. Infants respond differentially for as long as four months after birth to specific sounds that they experienced prenatally.

Perinatal is the period just before and after birth. Abnormal numbers of chromosomes are usually caused by an error in the separation of chromosomes into appropriate daughter cells during meiotic division. Risks for chromosome anomalies increases as maternal age increases. The age of the father plays a role in the likelihood of schizophrenia and autism.  DNA methylation abnormalities in the sperm of ageing fathers may be transmitted to offspring and confer risk for a range of neurodevelopmental and psychiatric disorders. Autosomal genetic disorders are disorders resulting from a mutation in a gene in one of the non-sex chromosomes, such as dwarfism, and risk for this increases as the age of the father increases.

Severe usage of alcohol during pregnancy can lead to cognitive and behavioural impairments and mild to severe physical anomalies. Alcohol has detrimental effects on the development and function of the placenta. Alcohol cannot be filtered by the foetus’ liver yet, so the foetus receives the unfiltered alcohol. Smoking is also a severe risk for foetuses, as it can cause a growth restriction. It is also associated with behavioural problems and cognitive weaknesses of the infant. Prenatal exposure to psychoactive substances prescribes to treat maternal conditions may result in a higher risk for adverse neonatal outcomes.

Specific nutritional requirements must be met for healthy foetal development. An adult disease that is associated with specific prenatal challenges during particular time windows is called developmental programming.

Maternal psychosocial stress during pregnancy has been linked to negative birth outcomes, such as alterations in foetal neurobehavioural development. It is possible that some stress is beneficial for the new-born, but the amount of stress must not be excessive.

A new-born has several reflexes that will disappear during the first year, such as the toe-curling reflex and the stepping reflex. The more active a foetus was, the more fussiness and inconsistent behaviour the infant will show.

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Comments, Compliments & Kudos

Question about development

Hei Jesper!

Thank you for your summary. It is super useful.

I have two questions regarding this chapter.
1. Could you please explain a little more the vestibular system development in preterm babies?
2. Is there a time frame in which fetuses are more affected by risk factors, or are they as dangerous in any part of the pregnancy?

Thanks!

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An Introduction to Developmental psychology by A. Slater and G. Bremner (third edition) - Chapter 5

An Introduction to Developmental psychology by A. Slater and G. Bremner (third edition) - Chapter 5

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Visual acuity is the ability to make fine discriminations between the elements in the visual array. Infants’ vision is poorer than that of an adult. Visual accommodation is the ability to focus on objects irrespective of their distance from the eye. Infants are not good at this either. There are several ways to test infants their vision:

  1. Visual preference method
    Infants are shown two objects and the object they look the longest at is the one they have a preference for.
  2. Habituation techniques
    Habituation shows the existence of visual memory and this tests whether infants can discriminate between two objects by presenting them sequentially and seeing whether dishabituation occurs.

Infants are able to discriminate between simple shapes. This even occurred in new-borns, showing that new-born infants perceive simple shapes as a whole and not just as a collection of parts.

Size constancy is the understanding that an object remains the same size despite its retinal image size changing as it moves closer to or away from us. Shape constancy is the understanding that an object remains the same shape even though the retinal image shape changes when it is viewed from different angles. New-borns already understand the principle of size constancy and shape constancy. Object unity is the understanding that an object is whole or complete even though part of it may be hidden. 4-month-olds perceive object unity already. It is likely that infants use common motion to perceive object unity. New-borns do not perceive object unity. 6-month-olds perceive trajectory-continuity, whereas 4-month-olds only do so when the occlude is narrow. Subjective contour is when only parts of an object are presented, the remaining contours are filled in, in order that the complete shape can be perceived. 4-month-olds perceive subjective contour, especially when the object is in motion. They also perceive this as an occlude.

Face perception emerges at around 2 months, although evidence suggests that a form of facial perception is present at birth. The two-process account of newborn face perception states that new-born preference for faces stems from an innate subcortical mechanism that leads new-borns to attend preferentially to faces of the same species. After the second month of life, this is replaced or supplemented by an experientially based mechanism that involves a diffuse network of cortical areas and allows for continues cortical specialisation and tuning to specific faces. An alternative view is that new-borns prefer certain properties of stimuli that are not face specific.

Infants have a preference for the face of their mother and can discriminate between their mother and other faces. 2-month-old infants and even new-borns will look longer at a face rated attractive by adults than non-attractive faces. The preference for attractiveness may stem from the preference for prototype faces. General abilities become more narrowly tuned as a result of experience. Infants are able to imitate already and this might play an important role in language development.

Very young infants are able to discriminate between certain speech distinctions that exist in other languages but not in their own. This ability is later narrowed to their own native language. Infants prefer motherese or infant-directed speech, the speech that adults use when addressing an infant.

Piaget stated that infants were not born with knowledge of the world, but gradually constructed knowledge and the ability to represent reality mentally. According to Piaget, prior to the age of 9 months, infants do not exhibit object permanence. It does not develop fully until near the end of the second year of life. The A, not B error is an object-searching error that is often made by 8-12-month-olds. Infants making this error will look for an object where they have most often found the object, rather than where they last saw it being hidden.

A limitation of Piaget’s work was that it relied on the infant’s ability to act upon the object. The violation of expectation technique is a technique where infants are shown an event and then shown two new events, one of which is consistent with reality and the other is inconsistent with reality. The infants will typically look longer at the impossible events because it violates their expectancies. This leads to the conclusion that 5-month-olds have object permanence. Even 2-month-olds have the ability of some sorts.

Spelke and Baillargeon argue that infants possess core knowledge of the world, which is basic information about the world. Infants reason about the number of objects involved in an action, as shown by research. Infants are able to discriminate between arrays in terms of numerosity, though only in the case of small numbers. Numerical competence was based on subitising, the ability to perceive directly the number of items without consciously counting. This only applies to small numbers and thus this ability disappears with larger numbers. Infants are also able to make very simple additions and subtractions, as shown by the time they looked at impossible events.

The idea that a lack of motor skill leads to not searching for an item seems false, given that infants will try to look for it when it is placed behind a transparent screen, but not behind a non-transparent screen. This shows that infants do not understand the relationships between objects and occluders, but this does not mean that infants do not have object permanence.

A possible explanation for the A, not B error is response preservation, which is repeating a previously learned response usually when it is no longer appropriate. Another possible explanation is a memory explanation, that there is interference between the location A and the location B and that the already existing memory predominates over the new memory. The problem with this explanation is that errors even occur when the object is in view in the new location. Another possibility is that through seeing an object hidden and finding it, infants quickly learn to treat place A as a container and that this knowledge, rather than knowledge about the object, prevents them from finding the object. There is a link between success and continued attention to location B during the delay. When attention is distracted, more preservative behaviour occurs. Another possible explanation is that the frontal cortex, which is involved in planning and guidance of actions and executive functions is still too immature to fully process the event. Successful B trials are positively associated with greater frontal EEG activation.

It is possible that infants do have knowledge about things such as object permanence and the movement of objects, but that they are not able to convert this knowledge to action. It is likely that Piaget’s model has to be remodelled by stating that infants do not gain knowledge by actively acting upon the world, but that they have the knowledge and by actively acting upon the world they create links between that knowledge and action.