Newborn babies show some characteristics that are universal in all human beings. They have inborn reflexes such as sucking and grasping, and they possess some basic sensory abilities. They also seem to be prepared for social interaction with other humans. Modern research shows that a baby responds to human faces almost immediately after birth. From early on, babies can exchange sounds and non-verbal signals with the mother or primary caregiver.  The innate capacity for social responses in newborn babies enables them to interact with others long before language develops.

The brain of a newborn has more than a trillion nerve cells that communicate across many trillions of synapses. The central nervous system continues to grow in size and complexity after birth. Synaptic growth is most significant in the first year of life, but it continues during childhood and into late adolescence. However, human brains are made for lifelong learning; neural connections can be formed throughout the entire life of an individual. The ability to develop and change in response to the environment is called neuroplasticity.

Maturation theory

Maturation theory was already rather dominant in the 1930s. Arnold Gesell argued that babies are born with a “developmental clock” that will determine when developmental milestones will occur – for example, when they will sit, walk, talk, and engage in abstract thinking. He argued that these milestones occur in a fixed sequence and at a specific time.  This theory would have a major effect on other theorists' "stage theories" - for example, Piaget's theory of cognitive development.

Konrad Lorenz also argued that child development was based on innate behaviours that develop during "critical periods." If the behaviour did not develop during that period, it would be impaired. This idea was also used by Bowlby in his theory of attachment.

Both of these theorists influenced our thinking about the brain, even though their research was not about the brain itself.  Instead, they were making assumptions about the innate nature of development.

Modern research argues that there are some aspects of development that are supported by the maturation theory.

For example, researchers have found that the development of vision is linked to brain maturation. At birth, babies have difficulty tracking moving stimuli.  At around one month, infants go through a phase of “sticky fixation” where they have difficulty shifting their gaze from one stimulus to another.  Sticky fixation ends at two to three months when we see maturation of regions of the parietal cortex.  At 4 to 6 months, the infant is able to anticipate the location of an object, in line with the maturation of the frontal cortex.

Le Grand et al (2001) found that infants with bilateral cataracts - that is, cataracts in both eyes - do not develop full visual skills, even if surgery is done at an early age. Even nine years after surgery, children still struggle with processing some facial information. This strongly indicates that there may be a critical period for the development of the brain's visual processing regions.

Modern technology makes it possible to investigate brain development by looking at glucose metabolism in various brain regions. Chugani (1999) reviewed a series of studies of newborn human babies done with a PET scan and found that there was little activity in the cerebral cortex, which is associated with higher-level functioning. There was high activity in the brain stem, which regulates inborn reflexes such as sucking or the startle reflex. The research also established that the limbic system -  including the amygdala, the hippocampus, and the cingulate cortex - was active in newborns. Chugani related the activation of the limbic system to the infant’s ability to read the emotional content of human faces, and to communicate via facial expressions and eye contact.

Bachevalier et al. (1999) found that if they lesioned areas of the limbic system in a newborn monkey, it gradually lost the capacity for social behaviour. Eye contact decreased and the animal showed blank facial expressions.  This indicates that reading facial expressions is to some extent an innate capacity, which can be lost due to brain damage.

From the age of six to nine months, the frontal lobes and the prefrontal areas of the cortex begin to function more fully, due to the growth and myelinization of neurons. There is also growth in areas of the brain such as the hippocampus, which plays an important role in memory, and the cerebellum, the control center for body movements. Psychologists believe that these changes in brain structure provide the physical basis for the child’s ability to engage in more complex motor behaviour and an increased ability to learn.

During middle childhood, growth in the area of the frontal lobes continues. Researchers hypothesize that the pattern of brain changes taking place between five and seven years of age enables the frontal lobes to coordinate the activities of other brain centers so that more complex behaviours become possible. These include attention control, forming explicit plans, and engaging in self-reflection. Evidence to support this theory comes from observations of humans with damage to the frontal lobes, as well as experimental research with animals. Individuals with frontal lobe damage are unable to plan ahead or stick to plans. They seem to have no self-control and they are easily distracted. These deficits are very similar to what we observe in young children.

 Teacher only box

There is no correct answer to this question. The development of the hippocampus is something that can be observed and measured over time, whereas the "sense of self," especially since children's communication skills are limited, is rather difficult to measure. Students should be able to explain which theory they prefer and as well as why it "makes more sense" to them.

Development of the brain during adolescence

When children reach their teenage years, they become able to think in more abstract ways. The brain changes taking place at this stage are less dramatic than those earlier in life, but they are no less important. Reorganization and myelinization of the higher brain centers like the prefrontal cortex continue at least until the age of 20. This enables teenagers to process information faster and to perform higher-level cognitive activities such as strategic planning. However, the area that controls impulses in the prefrontal cortex is among the latest brain regions to mature, at around 20 years.

Giedd (2004) undertook a longitudinal study of healthy children, carrying out MRI scans every second year. He found that 95 percent of the structure of the brain is formed when the child is five or six, but he also concluded that areas in the prefrontal cortex appear to grow again just before puberty. The growth spurt in synapse formation just before puberty is a clear illustration of how different parts of the brain mature at different times, and that the frontal cortex matures relatively late. However, this does not necessarily reveal anything specific about the relationship between behaviour and brain structures, although popular interpretations of neuroscientific findings have claimed that problem behaviour in adolescents is due to their immature brains.

 Teacher only box

Would you consider the fMRI studies on sugar and money valid studies?  Why or why not?

The fMRI studies have high levels of internal validity, but low levels of ecological validity.  In addition, they are quasi-experimental in nature.  Since the participants cannot be randomly allocated to conditions, we can only determine the level of the correlation, but we cannot determine cause and effect relationships.

What is Galván's explanation for why the reward system is not as active in adults?

In adults, the prefrontal lobe is developed, so there is a more rational approach in adults as to the value of the stimulus.

What implications does this research have on our understanding of the teenage brain?

It appears that the teenage brain is more stimulated by novelty and reward than adult brains.  This may have implications for marketing - e.g. the teenager is more likely to want that new iphone!  In addition, it means that education for teens will be more successful when it is stimulating and, although there may be routines, there are also novel events happening in the classroom.

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