THE ROUGH GUIDE TO PSYCHOLOGYness is already evident from week ten, and the rapid eye-movements
(REM), indicative of dream sleep in humans outside the womb, are seen
in the last third of pregnancy.
Touch is the first of the senses to develop, at approximately eight
weeks, with sensitivity initially apparent around the foetus’s lips and
cheeks. Taste and smell come next at about fifteen to sixteen weeks,
with accounts of foetuses swallowing more if their mother’s diet has
sweetened the amniotic fluid. What you eat as a pregnant mother can
even influence your baby’s tastes once he or she is born – for example,
children born to mothers who ate garlic during pregnancy show less
aversion to this taste later in life. From 22 to 24 weeks, the foetus begins
responding to sound, and by late pregnancy there’s evidence for the
recognition of different voices and speech sounds.
Foetuses show evidence of basic learning at 22 to 24 weeks. They
will start to ignore or “habituate” to a sound or touch that is repeated.
From 32 weeks, they show signs of associative conditioning, whereby
the repeated pairing of one stimulus (such as a prod) with another
subsequent stimulus (such as a specific kind of noise) leads the foetus
to expect the second event to follow the first. A study published in July
A foetus photographed at eighteen weeks.