Book T of C
Chap T of C
This is the 2007 version. Click here for the 2017 chapter 10 table of contents.
Babies inside their mothers experience lots of pressure and movement. But premature babies lying in a hospital crib do not receive nearly as much of this stimulation. To see whether additional stimulation might help premature babies, Rice (1975) randomly assigned a group of 30 prematurely born infants into experimental and control groups. The experimental group was stroked and massaged over the whole body for 15 minutes, four times a day. Babies in the control group received normal hospital care without a daily massage.
What research did Rice carry out with premature babies?
At the age of four months, the babies in the experimental group were more advanced in their development. They had better motor reflexes and were "more socially adaptive and aggressive," responding more to their caretakers. Rice also noted that the babies seemed to enjoy the experimental treatment.
Infants quieted, smiled, established eye contact and vocalized. Mothers observed this behavior with interest and pleasure, relating their belief that the "baby likes being stroked and held by me." (Rice, 1975)
How did later research by Field support Rice's finding?
By the late 1980s many researchers agreed that touch played a critical role in development. Researcher Tiffany Field found that massaged infants gained weight 47% faster than non-massaged infants. This happened even though the two groups ate the same amount. Massaged infants typically left the hospital six days earlier, saving an average of $3,000 in hospital costs (Trotter, 1987).
How does touch have its effect, and how did research on rat pups demonstrate this?
Why does touch have this effect? Apparently touch stimulates brain chemicals that are crucial for growth. Researcher Saul Schanberg and associates at Duke University demonstrated this with rat pups (newborn rats). A chemical called ODC (ornithine decarboxylase) disappeared from the rat pups' brains within 30 minutes after the rat babies were separated from their mother, and the rat pups stopped growing. ODC is an enzyme that stimulates production of several other crucial brain chemicals. Normally mother rats lick their young, which stimulates the release of growth hormones. Schanberg demonstrated the same effect in laboratory experiments.
"I couldn't get the lab technicians to actually lick the pups," says Schanberg. But Gary Evoniuk, also of Duke, observed that stroking them heavily with a wet paintbrush had the same effect. (Barnes, 1988)
Rat pups receiving daily wet paintbrush stimulation gained weight faster than other pups, although receiving the same number of calories in their food. We can reasonably assume that a mechanism like this operates in humans, because the findings from Tiffany Field are strikingly similar, especially finding weight gain without any difference in caloric intake.
What seems to be the reason stress in mothers lowers the birth weight of babies?
These findings may also explain why mothers who are under a lot of stress during pregnancy often have underweight babies. Stress releases the pain-killing drugs called endorphins from the human nervous system (p.107). Endorphins inhibit the production of ornithine decarboxylase, the brain hormone that stimulates growth. Duke researchers found they could duplicate the growth-stunting effects of separating rat pups from their mothers by injecting rat pups with endorphins.
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