I attended a nice Siltamat lecture at the Psychology department of the University of Helsinki. Here’s a summary.
Sense of touch starts working at 8 weeks, muscular response to touch at 12 weeks. Pain is felt.
Sense of smell and taste is very accurate. Babies can identify their own mother’s milk even after a 3 month pause. The sense gets accustomed to all the smells and tastes that are delivered to the baby from the mother. So eating garlic during pregnancy means the baby will prefer garlic as well. Fetuses also swallow, and the rate of swallowing can be used to detect how much they like a certain flavour (girtls like sweet more than boys).
Sense of hearings starts working at 18 weeks. The fetus hears the body sounds of his mother, and his mother’s voice quite accurately. From the outside world he can hear many sounds, and can discern between different vowels and different pronounciation. During the last 12 weeks, the baby learns and remembers the sounds, music, and speech he hears.
A newly-born baby prefers heart beats, talking, and other familiar sounds. He will prefer talk over talk-like sounds, his own mother’s voice over that of others, and his mother’s language over others. The distinction is based on the prosody of the talk (melody and rythm). The baby will also prefer music his mother listened to during pregnancy over other music, songs sung by his mother over other songs, and his mother’s singing voice over that of others. The baby uses the sounds he already knows (and their emotional content) to match with visual impressions of facial expressions to learn what they mean.
Birth weight and cognitive development
The optimal birth size in BPM (height divided by weight cubed) is 29 or more. Shortened pregnancy will cause babies to be born underweight, but that is not as problematic as a baby that is full term, but still births underweight. Low birth weight can be caused by the smallness of the mother, smoking, and stress.
Low birth weight will correlate with:
- increased risk of type II diabetes
- tendencies of fearfulness, sadness, frustration, and ADHD
- cognitive skills (also height and head circumference are connected)
Even a single extremely traumatic event (like an earthquake) can shorten the length of pregnancy. Short pregnancy is also connected with heightened risk of depression at older age. And malnutrition during the first trimester is correlated with higher risk for schitzofrenic symptoms.
The health effects of these physiological factors are stronger in boys than in girls, but cognitive effects show no bias. All effect can be altered by the positive influence of the parents and the environment.
Final note: Smoking at the rate of 10 cigarettes / day even before the pregnancy will cause a significant drop in the IQ scores of the child at the age of 56 months.