Is It "Normal" to
Suck Your Thumb?
by Katherine Dettwyler, PhD
Department of Anthropology,
Texas A and M University
This was originally sent in a note to LACTNET in
response to a doctor suggesting that all children should be encouraged to suck their
I wrote this in response to an e-mail from a doctor in
Switzerland (not our friend Jim Akre from WHO) who took offense at my statement in my
chapter on weaning from the book that it wasn't normal/natural for human children to suck
their thumbs or fingers, and that such behavior was a sign of a child whose needs weren't
being met at the breast. He countered that self-comforting was a good talent for
infants/children, and that even fetuses in the womb sucked their thumbs. When I finished
writing this I decided maybe you'all would like to read it.
Re the thumb-sucking issue -- it is certainly true that
ultrasound and photography in the womb shows fetuses sucking their thumbs, but then
breasts/nipples aren't available in the womb, but the suckling instinct is clearly present
from an early age. Once the baby is born, however, the suckling instinct is supposed to be
directed toward the breast, to get the child nutrition and immunities, and the sucking
itself lowers the baby's heart rate and blood pressure. While it can be convenient
for the parents to have the baby suck on their thumb or fingers or pacifier (like
in the car on trips, or when mother is trying to cook dinner) it nevertheless is clear
from both cross-cultural and cross-species field studies that, given complete contact with
mother and free access to the breast on demand, human children (and young of our close
relatives, the great apes) do not suck on their thumbs or fingers. I never saw a child in
Mali sucking its thumb or fingers, in almost three years of watching/observing/studying
mother-child interactions. Likewise, thumb sucking is reported to be completely absent
from cultures such as the Navajo, in highland Papua New Guinea, Ecuador, the Peruvian
Andes, Mexico, Nepal, India, Tanzania, Botswana, and South Africa. A number of other
ethnographic studies of breastfeeding don't mention thumb sucking one way or another.
Thumb sucking is also absent from the great apes
(chimpanzees and gorillas) except among zoo nusery raised animals.
I think it is clear that human children have sucking
instincts that can persist until 7 or 8 years of age, or even longer, and must meet those
needs somehow -- through thumb, finger, or pacifier, if not allowed to meet them at the
breast. But I also think that meeting those needs at the breast is the
"normal/natural" context or situation, and involves not just lowering the heart
rate/blood pressure, but also the transfer of nutrients and immunities, as well as helping
the child with thermoregulation from being in contact with its mother's body. It may be
that thumb/finger/pacifier sucking "tricks" the child into being
"pacified" for the time being, even to the extent of reducing the time spent at
the breast. That doesn't mean it is good for the child. In fact, finger and thumb sucking
often lead to orthodontic problems. In the U.S. orthodontists even have evil-looking
devices they will install in a child's mouth to make it painful for the child to continue
sucking their thumb/fingers, in order to break them of this habit. If the child were
allowed to meet those sucking needs at the breast, it wouldn't lead to orthodontic
problems (in fact, just the opposite, with less orthodontic problems in long-term
Any time you force the child to rely on their own resources
prematurely, you must expect deleterious consequences. When the child's needs are met
through person-to-person interaction with its mother, you establish the primacy of social
contact, and the interdependence of human beings, rather than encouraging/forcing the
child to meet its needs by itself.
This may be a crude analogy, but consider this: If you have
two adults, married to each other, who have all the children they want and don't want to
get pregnant, but still have strong sex drives, would you consider it better
if they each went into a separate room and masturbated? This would certainly allow them to
"self comfort" and would make them independent and autonomous, so that one
wouldn't have to wait until the other was ready or "in the mood." Would you
really consider this an improvement?
[The next section was written a few days later, after a
number of people expressed disagreement.]
More thoughts on thumbsucking:
Of course all babies are different, and some develop the
habit of sucking their thumbs in utero, and moms don't think anything of it, so it
continues. Evidence based on cross-cultural research and analysis of human breast milk
content suggests that human babies are designed to nurse *several times an hour* around
the clock. One would expect that their has been selection for a strong instinct to suck in
this pattern, and nursing *on demand* can be altered significantly by the mother, who of
course has other things to do. I'm not suggesting that all babies must be held
continuously by the mother with continuous access to the breast -- just that that is what
they have evolved to expect, and their sucking instincts have evolved accordingly. When
you look at mothers who say they are nursing *on demand* but the baby only *demands* every
3-4 hours, you usually find subtle and not-so-subtle messages from the mother that nursing
more often is not allowed. Thus, baby may turn to his thumb or fingers, and since mom
thinks "baby can't be hungry again" she lets him pacify himself.
My own research suggests that the absolute minimum time
human children have evolved to expect breastfeeding to continue is 2.5 years, with a range
of 2.5 to 7 years. Thus, one would expect that for many of them, their sucking instincts
will remain strong throughout this period, and thus one would expect a child nursed for 2
years to be very likely to still have the instinctive urge to suck til 6, 7, 8 years or
even longer. I strongly encourage parents of thumb-suckers to let their children suck
their thumbs (fingers, pacifiers) as long as they need to.
I was responding to a Swiss doctors claim that all children
should be *encouraged* to suck their thumbs to make them more independent of their mothers
as early as possible. He was saying that self-comforting is better than comforting at the
breast. I disagree. That's all.
Prepared November 28, 1995. Updated November 30, 1995.
Last updated September 23, 1999, by sak.
Contents copyright 1999 Sue Ann Kendall and Kathy
Dettwyler. Thanks to Prairienet, the
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