Are men superior in visuospatial skills ?

Read Also

 It is commonly stated that men have superior visuospatial skills (maccoby & Jacklin, 1974).  This is also an overstatement.  While it is true that men are indeed significantly better on certain mental rotation tasks,  and discrimination of angles, there are several tasks requiring visuospatial analysis where it is women who are slightly superior.  For example,  women slightly outperform men on digit-symbol coding tasks,  tasks which typically form one of the so-called "Performance" IQ subtests.   Such tasks require matching of pseudo-geometric symbols (their discrimination, recognition and copy require visuospatial processing) with numbers by looking at exemplar pairs and completing matches of numbers by drawing in the missing symbols as fast as possible.     I have a feeling (it is a gratuitous speculation)  that if the time constraint were removed,  men would achieve a small advantage.  However,  even when there is no time constraint,  women do as well as men on some visuospatial tasks.  Rey's Complex Figure Test provides a case in point.  This test comprises a very complex figure comprising many angles and numerous different frames.  As far as my intuition goes,  this is a very "visuospatial" test.  The figure must first be copied,  and after several minutes of delay, it must be drawn from memory. There is no time constraint with regard to the time available for drawing.  Women do as well as men on this test. I suppose social gender-role specialists would love to argue that men could very well have superior mechanical reasoning abilities,  and by extension, visuospatial abilities,  because of their childhood and adult life experiences (taking apart toys for example).  But here's a challenge for the social gender-role approach:   If shown a beacon with a liquid in it,  a ground line,  and a water level,   men will detect more often correctly and more rapidly whether the water line is correctly parallel to the ground-line or not.   Who would seriously want to argue that men have more experience pouring liquids from beacons or containers ?  Beer drinking does not qualify when one drinks from the bottle...  Men are frequently found to have a just barely significant advantage on visual disembedding tasks.  Such tasks require that geometric forms (such as a three dimensional cube) be discerned even though they are hidden or embedded in a complex arrangement of lines and angles.  In my own research,  I have been compelled to recognize the male superiority in at least one aspect of visuospatial processing.  In an investigation of 175 men and 175 women,  very well matched for age and education,  I found that men were significantly superior on a test called the Porteus Mazes test.  In this test the subject must draw a line from the center of a complex maze,  avoiding numerous dead end channels, to finally emerge at one extremity of the maze.  The test can  be completed most efficiently if the person is able to visualize the whole path,  keep it in memory,  and then draw the trajectory in a single go by duplicating the mental image.  Though these were very large groups,  the sex difference was barely significant.  Yet to my surprise,  it transcended another much touted sex difference, namely the female advantage in verbal fluency.  Indeed these same subjects had completed a verbal fluency test called the Controlled Oral Word Association Test (COWAT).  Though the women did better,  the sex difference did not reach the threshold for statistical significance. Years later,  I came to realize that Porteus himself had observed the same sex difference on his own test when he compiled his own norms.  This sex difference has often been ignored in the mainstream literature.  The advantage of men on mental rotation tasks is probably the best established male advantage.  Tests which show this sex difference are of several sorts.  Several tests of visual aspects of mechanical reasoning have been found to yield this effect.  Another procedure consists of depicting a number of tridimensional (height, length, depth) block constructions rotated along one or two axes (right/left,  front/back) and requiring the subject to identify which assemblies are the same and which are different.    Finally,  one test presents to the subject pictures of tridimensional cubes with one or several black or white sides out of the total of six.   The subject must then look at unidimensional models, resembling flat paper cut-outs of the cubes,  as if prior to their being folded into the tridimensional cubes.   The subject is required to discriminate identities and differences between the uni and tridimensional versions.

A biological determination of male superiority for visuospatial processing,  would seem far more plausible to me if it were consistently observed in other species.   Don't you feel the same way ?  Male rats consistently learn to negotiate a maze (labyrinth) more quickly and with fewer errors than females,  -even though there are many other forms of learning where they have no superiority to females (object discrimination,  etc.).  It is even more interesting to note that a single feminizing injection of the male rat fetus will prevent him from showing the male-typical advantage at adulthood.  Likewise,  a single masculinizing hormonal injection of the female rat fetus will procure for her the male-typical advantage in maze learning.  However,  not all of the hormonal determination of this sex difference is prenatal (organizational).  One study found that the male rat advantage in spatial learning could be reversed by a single dose of estrogen applied to adults.  Furthermore,  one recent study found that female rats are worse at estrous than at diestrous,  and that female rats show a decrement in spatial learning following ovariectomy (removal of the ovaries).  Hormonal determination of cognitive differences between the sexes is an ongoing affair throughout life.  Researchers have even been able to show that female rats,  like women,  prefer to navigate in a maze by using object-markers situated along the trajectory,  -whereas male rats, like men,  prefer to rely on coordinate-space markers,  and ignore the objects along the way.    Here's what I mean by use of "coordinate-space" markers.   You want to go visit aunt Harriet at the other end of town.  You have been there once before,  ten years ago.  You don't bother looking at the map, or asking for directions.  You hop into your car,  and rely on your image of the trajectory -which in your memory is a mere vector (direction).    You figure she lives exactly Northwest from you ten miles away,  so you just head out in that general direction,  doing the right and left turns often enough and regularly enough to keep you on that vectorial track.  I tried to find evidence in the literature of a spatial advantage of male monkeys.  It seems that such important research,  on the specific theme of visuospatial ability, remains wanting.  The rat model of cognitive sex differences in visuospatial ability is extremely useful and convenient but it would be truly useful and important to carry out such studies with monkeys  -a wonderful doctoral thesis for the taking.  Even the rat model is problematic.   For example,  because there exists an intimate link between estrogen and androgen metabolism in the brain, masculinizing effects of estrogen injections on brain anatomy [SDN-POA] and behavior have been found by the neuroendocrinologist Dohler.  And two researchers named Williams and Meck found that even lordosis and maze learning could be maculinized in female rats with injections of estrogen.   So in fact,  our knowledge of the effects of prenatal manipulation of the brain with hormones remains piecemeal.  The effects probably depend on the brain site,  the developmental timing,  the dose, the molecular variant of the injections,  and of course on specific behaviors investigated.   As I explain elsewhere in this book,  virtually nothing is known about such phenomena in humans,  aside from a few studies on humans exposed prenatally to the synthetic estrogen diethylstilbestrol.

If spatial ability is determined by prenatal hormonal influences on the development of the brain in humans, as it most likely is in rats,  then human females hormonally masculinized before birth (either within the normal range or beyond) ought to show a visuospatial superiority compared to their unaffected sisters.  Conversely,  men with partial prenatal hormonal feminization should be weaker on visuospatial tasks.   This is roughly what has been reported.   Eleanor Maccoby and her colleagues measured androgen levels in the umbilical cords of normal mothers and then tested the cognitive abilities of the progeny 6 years after birth.   The only relation found was for high androgen levels (in the female range) to correlate positively with (i.e., to predict) high visuospatial ability in girls. In a more recent investigation by Gina Grimshaw and her colleagues, relations were examined between prenatal testosterone levels in 2nd trimester amniotic fluid and lateralization of speech, affect, and handedness at age 10.  Girls with higher prenatal testosterone levels were more strongly right-handed and had stronger left-hemisphere speech representation. Boys with higher prenatal testosterone levels had stronger right-hemisphere specialization for the recognition of emotion. The authors claimed that this pattern of results is most consistent with Witelson's (1991) claim that prenatal testosterone leads to greater lateralization of function.  One study has investigated boys with very low androgens at puberty (presumably of prenatal origin).  These boys had significantly weak visuospatial abilities.  Women whose mothers had adrenal hyperplasia,   resulting in excessive secretion of androgens into the blood stream and thus moderately and abnormally masculinizing the fetus,   have been found to manifest superior visuospatial abilities  -characteristic of men.    Boys born to diabetic mothers treated during pregnancy with high levels of estrogen had lower visuospatial ability than controls. Studies of testicular-feminized humans (androgen insensitivity syndrome,  see chapter 7) and of kwashiorkor protein deficiency testicular feminization syndrome have both found that so-affected men have a feminine cognitive profile:  relatively higher verbal than spatial abilities.   Kwashiorkor is due to a certain type of undernourishment (protein deficiency).    The liver of so affected boys cannot break down estrogen as efficiently as normal boys.   Estrogen then accumulates and partly feminizes the body,  including the brain.