Peter's Believe It Or Not -- The Water Level Test
Date: Wed, 16 Jun 93 16:15:42 PDT
Subject: Peter's Believe It Or Not -- The Water Level Test
From: bostic@vangogh.CS.Berkeley.EDU (Keith Bostic)
From: Sex Differences in Cognitive Abilities (1986) by Diane F. Halpern:
Piaget and Inhelder [(1956) The Child's Conception of Space] believed that
the knowledge that water level remains horizontal would be attained at an
average of 12 years. It seems that girls know this principle at a later age
In fact, it has been estimated that 50% of college women don't know the
principle that water level remains horizontal. This is a surprising
result that has been replicated several times. It is difficult to
understand why this should be such a formidable task for college women.
(See Harris, 1978, [Sex Differences in Spatial Ability, anthologized in
Kinsbourne, M. (ed.), Asymmetrical Functions of the Brain] for a review
of research in this area.).
The principle that water remains horizontal when a glass is tipped seems
particularly difficult for girls to comprehend, and the large sex
differences found on the [Piaget & Inhelder] Water Level Test cannot be
explained by psychosocial factors. Thomas, Jamison, and Hammel (1973)
[Science, 181, 173 - 174] reported very little success in teaching this
principle to girls.
In [the Water Level Test] subjects are required to draw in the water level
in a picture of a tipped glass. The usual finding is that far fewer
females draw a horizonatal line to represent the water level than males.
Females tend to draw their line parallel to the direction in which the glass
is tipped. This is a robust result that has been replicated many times with
samples ranging from elementary school-age children to college students.
This task really requires two component skills: (1) Subjects must know
that water will always remain horizontal even when its container is
tipped; and (2) Subjects must be able to draw an approximately horizontal
It is difficult to understand how either of these two skills could depend
on sex related environment differences. It does not seem likely that
males have more or better experience with a tipped glass of water. In
fact, one could argue that females, the primary cooks and dishwashers in
many homes, might have more related experience with tipped glasses of
water and other liquids than males.
Nor does it seem likely that females are less able to express this
knowledge with an approximately horizontal line. The ability to draw an
approximately horizontal line is a "low level skill." Even if boys play
with spatial toys like tinker toys and Lincoln logs more often than girls
and are encouraged to pursue spatial professions like architecture and
engineering, it does not seem intuitively obvious that these experiences
are needed in order to be able to approximate a horizontal line.
There is, of course, no simple or direct biological explanation for
these results either. I do not think that there is a genetic code
for performance on the Water Level Test.
© 1993 Peter Langston