Evolutionary Psychology
Lecture 10: Spatial Ability.
Learning Outcomes.
 At the end of this session you should be able to:
 1. Discuss the adaptive nature of spatial ability in
animals and humans.
 2. Discuss evolutionary explanations for sex
differences in spatial ability.
Adaptive Significance of Spatial Ability.
 Evolutionary theory predicts sexual dimorphism when
males and females face different adaptive pressures.
 Variation in hippocampal size (the seat of spatial
processing) may be related to the degree of selection for
spatial processing.
 Jacobs et al., (1990) argued that spatial ability should
evolve in direct proportion to the navigational demands
that an individual faces in everyday life.
 Whilst males and females share the same environment,
they may exploit their environment differently.
 In polygynous species males traverse large ranges to find
mates, and such species should show greater sex
differences in spatial ability than monogamous species.
Typical Range Sizes.
Male
Polygynous species
Monogamous species
Female
From Gaulin, 1992 p 130,131.
Spatial Ability in Polygynous
Versus Monogamous Voles.
Polygynous
Polygynous
Monogamous
From Alcock, 1998, p 112
Hippocampal Size in Voles.
 Jacobs et al., (1990) compared hippocampal size in the
polygynous meadow vole and the monogamous pine vole.
 During the breeding season, adult males and females of
each species were captured and the hippocampal area was
determined.
 In the polygynous species male hippocampi averaged 11%
larger than the female hippocampi, in the monogamous
species this differences was only 2%.
 These differences were independent of body size.
 However, a problem could be that males, having typically
larger bodies and brains may thus happen to have larger
hippocampi as a matter of course.
 Further evidence is required:
Range, and Hippocampal Sizes in Voles.
Home range
From Sherry et al., 1992, p301
Hippocampal size
Evidence From Species Where
Females Roam.
 Sherry et al., (1993) looked at hippocampal size in the
parasitic brown-headed cowbird.
 Females search for host nests while males do not.
 Spatial memory for the location of prime nests is a key
requirement to successful egg laying.
 The authors did indeed find that the hippocampus was
larger in cowbird females than males.
 There was no such difference in related but non-parasitic
species, where males and females have similar spatial
demands.
 This suggests it is spatial activity and not sex per se that
influences relative hippocampal size.
Between-Species Comparisons.
 Sherry et al., (1992) looked at spatial memory and
hippocampal size in food-storing and non food-storing
birds.
 Food-storers store single items of food in several hundred
cache sites scattered throughout their home range during
winter.
 They then revisit these sites on subsequent days by
remembering the precise spatial location by learning
geometric relationships among landmarks (Kamil & Jones,
1997).
 The authors reported that food-storers (black-capped
chickadees, jays and nuthatches) had a hippocampus more
than twice the size than that of non-storers.
 This was independent of sex.
Human Sex Differences in
Spatial Ability.
 Voyer et al., (1995) concluded that the largest male
advantage was in tests of mental rotation, a moderate
advantage in tests of spatial perception (e.g. rod and frame
test) but no clear difference in spatial visualisation (e.g.
embedded figures test).
 Males are also better at spatial interception and throwing
tasks (Halpern, 1992).
 Such differences are seen cross-culturally, and appear to
have remained fairly stable over time.
 This indicates that while social factors may influence the
expression of spatial skills, the sexes may be different
before societal factors can have an influence.
 There are several evolutionary explanations for human sex
differences in spatial abilities:
1. The Mating System Model.
 Gaulin (1992) proposed that cognitive mechanisms
underpinning spatial ability are navigational adaptations.
 Individuals need to be able to find resources, to return to
them, and to remember to avoid dangerous areas.
 This requires the ability to acquire, store, process,
manipulate, and retrieve spatial information.
 The intensity of selection for such abilities should be
proportionate to the magnitude of these demands.
 Social primates such as chimpanzees display sexually
dimorphic ranging patterns with males travelling further
than females as they patrol the boundary of their territory.
Human Ethnographic Evidence.
 Like chimpanzees, it is generally accepted that humans are
a species of polygynous ancestry with males searching out
females, therefore natural selection would favour males
who had superior spatial abilities.
 Many ethnographers have noted that males travel more
widely than females.
 For example, Hewlett et al., (1986) investigated travelling
behaviours in the Aka Pygmies of central Africa.
 Males had significantly larger exploration ranges.
 On the basis of the ‘Mating Systems Model’ we would
predict that on various aspects of wayfinding and route
learning, males should outperform females.
Wayfinding.
 It has been proposed that males and females may use
different strategies to solve real-world spatial problems.
 Males may use a geometrical strategy relying on the
Euclidean properties of space (co-ordinates from angles,
distances etc).
 Females may use topographical properties (the presence of
and configural relations among landmarks).
 For example, McGuinness & Sparks (1983) noticed that
when asked to draw maps of their campus, female students
spontaneously drew more landmarks than did males.
Wayfinding Studies.
 Miller & Santoni (1986): Presented males and females with
schematic maps of a town consisting of streets with
landmarks. They had to look at each map for 10min and
then give precise directions from one part of the map to
another.
 They then looked at the map for a further 5min and had to
answer 10 questions concerning directions between various
locations on the map. They found:
 Older participants were more accurate.
 Males were more accurate than females particularly on the
maps with irregular street arrangements.
 Females were more likely to rely on landmark cues.
 Males were more likely to rely on geometrical cues.
Miller & Santoni (1986)
Second Study.
 They used older participants, and made a note of which
courses they had taken in high school or college.
 They also recorded the relative use of active versus passive
transport.
 The same differences emerged in wayfinding knowledge
with males outperforming females, and females relying
more on landmark cues.
 They found positive correlations between:
 Accuracy scores on this test and active transport.
 Accuracy scores and type of courses studied.
 Males had higher active travel scores and were much more
likely to have taken courses such as geometry and
trigonometry.
Galea & Kimura (1993).
 Males and females learned a route through a novel map to
criterion and then answered questions about the landmarks
and the geometric properties of the map.
 Participants also received various cognitive tests. They
found that:
 Males performed significantly better on all measures of
route learning.
 Females recalled and recognised more landmarks and
street names.
 Males better recalled the geometric properties of the map.
 Males performed significantly better on the MRT.
 Males and females did not appear to differ in their use of
strategy to learn the route, both used a spatial strategy but
males were more effective.
Other Studies.
 Lawton et al., (1996) led students on a circuitous route
through hallways in a campus building and then asked to
find their way back to a starting point.
 There were no sex differences on time to complete the task
but males were more accurate on the direction task.
 Dabbs et al., (1998) asked 90 males and 104 females to
complete cognitive spatial tests, give directions from a local
map and identify places on a world map.
 Males outperformed females at mental rotation, used
Euclidean directional terms (such as 'East', 'West') while
females gave more landmark information and males
correctly identified more places on the world map.
Silverman et al., (2000).
 Led participants along a 400m
circuitous
path
through
woodland with no visible
landmarks.
 During the walk, participants
were asked to place an arrow
pointing in the direction of
where the walk began.
 At the end point participants
were required to lead the
experimenters back to the
start point by the most direct
route.
 Males performed better on
both tasks.
From Silverman et al., 2000, p206
2. The Division of Labour Model.
 Silverman & Eals (1992) argued that the critical factor in
selection for human spatial dimorphism was sexual division
of labour between hunting and gathering during hominid
evolution.
 Males predominantly hunted whilst females predominantly
gathered.
 They predicted that males should excel in cognitive abilities
corresponding to hunting and navigational skills (mental
rotations, map reading, maze learning, throwing).
 Females would excel in cognitive abilities involving the
recognition and recall of objects (plants) within a spatial
array
Silverman & Eals (1992) Study.
 Participants studied an array of
familiar objects.
 On new sheets, they had to
firstly identify new items, and
then items that had moved.
 Females scored significantly
higher on both tasks.
Added items
Figures from
Silverman & Eals,
1992 p537-538
Moved items
Eals & Silverman (1994).
 Repeated
the
experiment
using uncommon objects.
 In an incidental version
females were better at object
recall, and significantly so at
location memory.
 In a naturalistic setting a
clear female advantage was
again
seen
for
location
memory.
Added items
Figures from
Silverman & Eals,
1992 p98-99
Moved items
Support for the ‘Gathering Hypothesis’.
 McBurney et al., (1997) used a gathering-analogue task
based on the game ‘Memory’.
 Players attempt to match pairs of objects depicted on cards
that are arrayed face-down on the table.
 Players can only turn 2 cards over in an attempt, and if they
match, they are removed.
 As more cards are revealed then players can recall the
locations of cards turned over previously.
 The authors argued that this game was a more ‘ecologically
valid’ gathering task.
 On this task, females performed significantly better, while
on the MRT males performed significantly better.
Female Advantage in
Environmental Awareness?
 McGivern et al., (1998) assessed recognition memory in
males and females using nameable objects, abstract
shapes, and patterns in incidental and directed conditions.
 Participants were presented with a sheet of items, which
they studied for 60s, the items were removed and they
received a different sheet and asked to cross out all of the
new items.
 Females recognised significantly more items than males in
each category in both direct and indirect conditions.
 The authors argued that this reflects a female advantage in
environmental awareness due in large part to nursing
demands - i.e. having to be constantly vigilant with young
children.
Male Hunting Prowess?
 If females are better at locating items within an array then
are males better at hunting skills?
 Watson & Kimura (1991) had male and female participants
perform spatial interception (catching table-tennis balls
fired in different directions from a launcher) and throwing
with both hands (hitting a target 3m away using a throwing
dart).
 Large sex differences favouring males were found on these
dynamic spatial tasks using either hand.
 The authors suggested that such skills would have been
vital for hunting and defence.
Wynn et al., (1996).
 Criticised both 'Mating System' and 'Division of Labour '
models.
 They pointed that out that it is not yet understood exactly
what cognitive processes are being used in the
performance of different spatial tasks.
 They also argued that the largest spatial sex difference
(mental rotation of 2D figures) exists on a test that has
little relevance to everyday life.
 Furthermore, ‘spatial perception’ which involves the ability
to pick patterns out of complex backgrounds has some
relevance (spotting a camouflaged animal) but does not
show a large sex difference. But could this also be used to
spot plants?
Lack of Archaeological Evidence.
 Wynn et al., (1996) also criticised the theories for their lack
of confirming archaeological evidence.
 For example, males are supposed to better at certain
spatiotemporal skills due to them developing superior
throwing/aiming skills through hunting.
 However, throwing projectiles appeared too late in human
evolution to have had much influence on the development
of these spatial abilities.
 They also argued out that both males and females would
have engaged in foraging behaviours (much like
chimpanzees) for the majority of human evolution, with
males only engaging in correspondingly greater hunting
activities much later.