At birth, babies’ internal organs are fairly complete, but their brains continue to develop for several years. The average weight of a brain grows from approximately 400 g at birth to 1 000g at one year and 1 100g at age two (80% of the weight of an adult brain). The brain develops in phenomenal fashion starting in the third trimester of pregnancy until the end of the first year of life. But to develop its generic potential, babies’ brains absolutely require social and emotional contact.

As early as the fifties, John Bowlby, a British psychiatrist, asserted that an attachment-based relationship with at least one adult was as necessary to children’s emotional development as food is to their physical growth. Along with Mary Ainsworth, an American psychologist, he developed the theory of attachment. Babies will develop “secure” attachment if they receive daily care from a sensitive adult who can read their signals and meet their physical and emotional needs in a fairly consistent manner. If they are regularly in relation with an adult who is inconsistent in their care, or who manifests little affection, they will develop “insecure” attachment.

Since the nineties, research in developmental neurobiology has shown how this attachment develops in babies’ brains and confirms that attachment bonds are a biological necessity. The brain’s right hemisphere is the first to develop in children.  Dominant in fetuses and babies up to age 3, the right brain is, among other functions, the seat of non-verbal aspects of communication, intuition, empathy, creativity and sense of self, both emotionally and physically. The left brain, verbal and conceptual, starts to develop mainly from the age of 3. A majority of researchers claim that the social environment during the first two years of life, particularly the mother-child bond, enables the maturation of the right brain. That is where the bases of social adjustment, stress-coping mechanisms and emotional control develop. As Jeliu and Cousineau put it, the brain is literally sculpted by communication experiences and by emotions felt during early childhood (2003).

Within the right hemisphere, it is mostly in the center of the brain, in the right limbic system, that the first socio-affective experiences are recorded in babies from age 0-2. During the first six months, there is an accelerated construction of cells and connections (called synapses) between neurons in the cerebral amygdala, located in the limbic system. At this age, babies are eager for social contact with all human beings. They have a deep interest in human faces. It is in the cerebral amygdala that reside the first associations they establish with many emotional states such as fear, joy, love – for example, “mommy, daddy, love me”, “when I am sad, mommy comforts me”, or “I can’t really count on anyone”. These experiences come through emotional contact with the mother and other loved ones, through visual cues, touch, caresses and sound, during daily care and play.

Then, around the age of 6 months, the amygdala matures and the more intense neurological development activity shifts to the callosal gyrus (first convolution above the corpus callosum) and nucleus septi. Babies now bond to known people who provide care and refuse contact with strangers. It is as though the neurological activity in the callosal gyrus and the nucleus septi inhibited the activity of the cerebral amygdala that eagerly sought out social contact with just anyone. Among people children trust, the mother is generally the favorite. The separation anxiety typical to the end of the first year appears.

From the second year of life, more intense activity can be observed in the orbitofrontal cortex (behind the eye socket). This cortex is the “higher management” of the socioemotional brain and plays an important role in emotional and behavioural self-control. Attachment quality, self-control and everything related (self-esteem, ability to empathize, etc.) continue to develop until adulthood, but the bases seem set by age 2 or 3.

If in the first six months babies are deprived of emotional contact, their amygdala remains functionally inert and “catatonic” behaviour similar to autism can be observed. Sadly, it has too often been observed in certain overpopulated orphanages. Deprivation of social stimulation after the age of 6 months may lead to children’s excessive familiarity with strangers, as though the callosal gyrus and nucleus septi, left unstimulated, could not inhibit amygdala activity. Jeliu and Cousineau (2003) explain that in some extreme cases of attachment system dysfunction, a kind of “social blindness” can be observed, an inability to identify and answer common social signals and great difficulty in remembering faces, people and places.

So the next time you feel you “haven’t gotten anything done today” other than caring for your baby, take heart in knowing that during this highly important day, you helped mold your baby’s brain with everything they will need throughout their entire life to relate to themselves and function in society.

Claudette Nantel,

Psychotherapist, pre- and perinatal psychology specialist

This article is presented by Maman Kangourou (

To know more:

- The limbic system:

a) (click the second link, “Physiologie émotions couleur. Pdf”, and scroll to page 23)

b) Scroll to the top third of the article to see the diagram of the brain. The article is highly technical, but great if you read English. This article by Schore is a classic reference for the neurobiology of attachment.

- Jeliu, G. and Cousineau, D. Le cerveau et l’amour maternel. 2003. PRISME, no. 40, pp. 118-125 – Drs. Jeliu and Cousineau are pediatricians at Hôpital Ste-Justine in Montreal.

- Sunderland, Margot. La science au service des parents. 2007. Montreal: Ed. Hurtubise – A book that addresses childhood education in terms of what is known about brain and nervous system development. - Rapport de recherche sur l’attachement, by Centre jeunesse de la Montérégie (2004) - Quebec experts discuss attachment, abandon, emotional deprivation and their effects on children. Particularly interesting for birth, adoptive or foster parents who are raising children having suffered difficult experiences in their first emotional relationships.

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