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Environment plays a major role in shaping the structure of the infant brain - and determining propensity

Patterns established in brain structure

The structure of the developing infant brain is a crucial factor in the creation (or not) of violent tendencies because early patterns are established not only psychologically but at the physiological level of brain formation.

The infant brain

Human infants are born premature by the standards of other mammals. Whereas a calf or foal can walk almost immediately at birth it takes a human baby twelve months to reach that stage. Much of their brain development takes place after birth, in early life, crucially before the age of three.

Between birth and age 3, the number of synapses (connections within the brain) increases twenty-fold from 10 trillion to 200 trillion. Because this is too large a number to be specified by genes alone, the new synapses are determined by experience (Shore, 1997). A baby is adding synapses at more than 1 million per second, responding to its experience of the world. During this period, synapses become ‘hard-wired’ by repeated use, implying very rapid learning via early life experience. Of course this process also has the effect of making early learned behaviour resistant to change. The experiences that serve to develop, hard-wire or prune different combinations of the trillions of synapses mean each baby’s brain develops differently in response to his or her particular environment. Extreme examples can be seen in children such as the neglected Romanian orphans, who lack activity in large areas of their brains, Native American Indians who grow up with acute hearing and balance skills – and modern children who find it difficult to function without TV background noise.

The new science of Epigenetics – nurture impacting nature

The new science of epigenetics demonstrates what is called the ‘gene-environment interaction’. This indicates that environment, especially during pregnancy and very early childhood, activates or silences ‘good’ and ‘bad’ genes crucial for mental well-being and social adaptation – in other words certain genes are actually switched on or switched off by early life experiences (Tremblay 2008).

Infant potential depends on quality of support received

These aspects of human development add up to the inescapable conclusion that the potential for an infant is defined by the quality of the support received in the very early, formative months and years. If the early experience is fear and stress, especially if these are overwhelming and occur repeatedly, then the neurochemical responses to fear and stress become the primary architects of the brain. Trauma elevates stress hormones, such as cortisol, that wash over the tender brain (Perry, 1995; Shore, 1997; Gunnar, 1996).

One result of such trauma is fewer synapses: specialists viewing CAT scans of the key emotional areas in the brains of abused or neglected children have likened the experience to looking at a black hole.

The brains of abused children are significantly smaller than the norm. Specifically: the limbic system (governing emotions) is 20-30% smaller and tends to have fewer synapses, and the hippocampus (responsible for memory) is also smaller. Both of these stunted developments are believed to arise from the toxic effects of the cortisol (Bremner et al, 1995; Bremner et al, 2003; Teicher, 2000).

Babies brought up in violent families are incubated in terror and their brains (and future prospects) can be permanently damaged.

Sensitive windows

During the first three years of life there are sensitive windows of time when specific learning takes place and the brain hones particular skills or functions. Certain elements of human capability, such as vision, language and emotional development, occur in spurts during these sensitive times. The size of the window is different depending on the skill. Synapse formation relating to sight (in the visual cortex) peaks at 3 months, finishing at age 3. An infant’s auditory map (hearing) is formed by 12 months. This accounts for why Japanese children who do not learn to distinguish between the letters L and R by 12 months have great difficulty in doing so ever afterwards. If the chance to practise a skill is missed during the window relating to that skill, a child may either never learn it, or the learning may be impaired.

Alan Schore is a scientist with the remarkable ability to remember everything he reads. Following a 10-year immersion in thousands of scientific papers on neurobiology, psychology and infant development, he concluded:

The child’s first relationship, the one with the mother, acts as a template…[that] permanently moulds the individual’s capacity to enter into all later emotional relationships (Schore, 2000).

To the best of current knowledge, the sensitive window for emotional sensitivity and empathy lies within the first 18 months of life, and these ‘skills’ are shaped by the prime carer’s interaction style. The wrong style can have disastrous results. Children reared in a loving, supportive (and non-violent) way are highly unlikely to develop the propensity to be violent, in any social conditions. Sadly, the reverse is equally true.