The same female nurse successively
stroked with one hand the infant’s legs, arms,
chest, or back (depending on whether the infant was
in a prone or supine position), and head for 10 seconds,
repeating the sequence for a total of 80 seconds.
The study period began when participants
were on average 28 weeks’ PMA and continued until
37 weeks’ PMA. In an effort to control for severity
of illness and under nutrition (as defined by head
growth), subjects were divided into 3 groups on the
basis of their degree of illness and head growth
during the stay in the intensive care nursery.