*
The
following is a draft book chapter I co-wrote for a book on Systemizing and
Empathizing which was to be edited by the originator of these terms - Simon
Baron-Cohen.
In the
draft, Patrick Rosenkranz and I put forward some new hypotheses for the
evolution of these personality traits - and these may be of some general
interest.
However,
the original contract for this book fell-through, and a new publisher is
being arranged. This means that there will be time, and need, for the draft
chapter to be revised considerably before publication.
Therefore,
if anyone has suggestions and comments for how this book chapter might be
improved these would be gratefully received.
**
Evolution of Empathizing and
Systemizing: Economic specialization and
the sexual division of labour
By Patrick Rosenkranz and Bruce G Charlton
Draft
version February 2013: , Psychology
Email:
brucedotcharltonatncldotacdotuk
Introduction:
What is it that needs to be explained?
The first
purpose of this chapter is conceptual clarification. In other words, we first
aim to clarify what an evolutionary theory of Empathizing and Systemizing needs
to explain. In other words, we need to be clear what has evolved, before we can
suggest why and how it may have evolved.
Therefore
we need to define the nature of both Empathizing (E) and Systemizing (S), and
to emphasize that they are personality traits rather than abilities. We
consider E as the disposition to apply ‘theory of mind’ (or social
intelligence) reasoning to experience; while Systemizing is a disposition to
apply non-social, abstract and systematic reasoning to experience. Therefore, E
and S are distinctive modes of thinking – in an identical situation, an
Empathizer would use one mode of thinking, while a Systemizer would use another
– even if both had the same underlying cognitive abilities, their preferences
or dispositions would be different.
To put
matters simply, E and S describe a fundamental orientation towards
either People or Things. An orientation could be understood in
terms of a spontaneous focus, a preference. The reason for an orientation may
be sought in terms of motivational systems of gratification and aversion: a
concern with either people, or things, will tend to give more pleasure (or less
pain) than its opposite.
But the
situation is not symmetrical for Empathizing and Systemizing, because man is a
social animal: thus a focus on people is to be expected, while a focus on
things in preference to people is unexpected, and invites specific
explanation.
In
evolutionary terms, we need to explain how it was possible that a preference to
deal with things rather than people was able to arise, specifically in men more
strongly than in women (Baron-Cohen, 2003)–
in face of our presumption that a preference for things over people would be
likely to provide a selective disadvantage in terms of social
relationships. In particular, this would probably be a disadvantage from the
perspective of sexual selection in its major form of female sexual choice.
In a
nutshell: we need to explain why ancestral women could have ended-up with a
mate who was more interested in things than they were interested in other
people (such as herself).
The
second (and main) purpose of this chapter is to describe specific hypotheses as
to how and why E and S traits may have evolved in ancestral humans, what may
have been their pay-offs in terms of reproductive success under specific
conditions, and to clarify the reason for the reciprocity of these traits and
the existence of sex differences(Baron-Cohen,
2003).
In brief
we regard Empathizing as the default human personality since, as the
application of social intelligence, it
reflects the great importance of social relationships to reproductive success.
By contrast, we regard Systemizing as having emerged later in evolutionary
history as a result of novel selection pressures due to changed economic
conditions - especially the development of more-complex humans societies (such
as agriculture and trade) with a variety of socially- essential, specialized
jobs for men.
These
evolutionary hypotheses are, at this point, necessarily speculative and
intended to serve as a guide for future empirical research rather than to
provide definitive answers.
Empathizing and Systemizing conceptualized as
personality traits
Empathizing
and Systemizing are conceptualized as personality traits, dispositions or preferences
to behave in certain ways; therefore not as cognitive abilities. E-S
variations are this not-necessarily correlated with cognitive abilities
– and indeed in some studies there is no significant measurable correlation
with cognitive abilities. For example, there is neither a strong nor consistent
association between the ‘reading the mind in the eyes’ test (a test of a
cognitive ability), and scores on a self-evaluation Empathizing scale (a
measure of disposition or personality): so that an individual may score highly
at reading the mind in the eyes but score low on an Empathizing scale, or vice
versa (Lawrence,
Shaw, Baker, Baron-Cohen, & David, 2004; Voracek & Dressler, 2006).
A
disposition is a personality trait: understandable as a sustained tendency, an
individual’s characteristic of habitually deploying a mode of cognition. A
disposition can also be seen as an individual’s preference for using an
ability. (In the sense that preferences can only select between a certain
set of abilities; one cannot characteristically be disposed to act in any way
that one is incapable of acting.).
And
preference to behave in certain ways is (presumably) based on a motivation, and
motivation is associated with a psychological reward (or gratification) from
doing something – or else a psychological punishment (or aversive consequence)
of not doing something.
Ultimately,
therefore, a disposition reflects that certain types of behaviour lead to
increased gratification (increased pleasure or diminution of suffering).
Individuals differ in the types of behaviour which lead to gratification, and
in the degree of gratification associated with a specific type of behaviour.
In sum,
individual and groups variations in Systemizing and Empathizing can be
understood as variations in the type of behaviour that (on average) lead to
gratification. Put simply, Empathizers gain enhanced gratification from
Empathizing behaviour, while Systemizers gain enhanced gratification from
Systemizing behaviour. For example, a High-Systemizer may have the ability to
understand and empathize with other people, but prefers to spend most of his
time doing crosswords; while a High-Empathizer may be able to do crosswords to
a high standard, but she would prefer to converse with a group of friends.
Naturally,
the disposition to be Empathizing or Systemizing requires that there be the
cognitive ability to do these; to empathize requires the ability to empathize
and to systemize requires that ability. And at extremes of disposition there
may be a deficit in such abilities, so that the extreme Empathizer may be
defective in systematizing ability and the extreme Systemizer may be defective
in theory of mind ability.
However,
deficiencies in either E or S ability are not necessary to the finding of
variations in E-S, and it seems that there may be a wide range of E-S
dispositions even when both abilities are fully intact. Therefore, these
abilities must have evolved in order that there be a disposition to use them.
Evolution
of the Social Brain
The
social brain hypothesis sees social selection pressures as the driving force
behind human brain growth: higher cortical functions have evolved to deal with
the adaptive problems of complex group living{Dunbar,
1995 #47} {Dunbar,
1995 #47}{Dunbar,
1995 #47}{Dunbar,
1998 #48}{Adolphs, 1999 #1}{Humphrey,
1976 #74}{Dunbar,
1995 #47}{Dunbar,
1998 #48}(Adolphs,
1999, 2009; Dunbar, 1995, 1998; Humphrey, 1976). The relative neo –
cortex growth in humans and other primates is due to the demands on executive
brain function required by living in complex social groups. Evidence in favour
of this hypothesis shows that as group size increases across primate species,
neo-cortex size also grows(Dunbar, 1995, 1998)
{Dunbar,
1995 #47}{Dunbar,
1998 #48}. The set of cognitive
adaptations that enables successful group living such as the abilities to
perceive, recall and process information about others and act according to this
information, is often termed social intelligence (Dunbar, 1998), Machiavellian intelligence
(Byrne & Whiten, 1988) or social cognition (Brothers, 1990).
Group
living poses a number of adaptive problems for the individual: attracting and
maintaining a mate, monitoring and manipulating social interactions, outwitting
rivals and forming alliances, inferring dispositions, motivations and
intentions of others, etc . Selection favoured those individuals who were the
most successful at solving these adaptive problems of group living. In order to
successfully survive and reproduce within a social setting, an individual
requires the cognitive ability to react adaptively to social challenges and to
affect others positively(Byrne & Whiten,
1988){Byrne,
1988 #122} {Byrne,
1988 #122}.
Amongst
the cognitive abilities enabling complex social interaction are face
perception, emotional processing, theory of mind (TOM), self-reference and
working memory (Grady & Keightley, 2002).
These abilities are mediated by interplay of activity of networks of
interdependent brain regions which support the behaviours necessary for social
interaction (Grady& Keightley, 2002).
Amongst the neural architecture that contributes to social intelligence are the
amygdala ventromedial prefrontal cortex and the right somatosensory related
cortex (Adolphs, 1999; Grady & Keightley,
2002).
An
individual clearly benefits in terms of reproductive success by being able to
predict the behaviour of others within the group, maintain beneficial social
relationships and even manipulating social situations to her own advantage(Byrne& Whiten, 1988; Humphrey, 1976). A
lack of the faculties required to function adaptively within the group can have
negative reproductive consequences for the individual. The inability to
positively affect others, at least to a degree, and to adaptively interact
within a group can lead to negative emotional effects for the individual,
social ostracism and ultimately, reproductive death .This can most clearly be
seen in the devastating effects of lesions and or disorders to the social
functioning of the individual(Ylvisaker, Feeney,
& Szekeres, 1998). For instance, individuals with the autistic
spectrum disorder have abnormal face perception (Klin
et al., 1999) as well as strong deficits in the theory of mind mechanism
(Grady& Keightley, 2002). Autistic
individuals have difficulties in adaptive social behaviour, avoid normal social
contact and are generally indifferent to social encounters (Baron-Cohen, 1997).
At the
core of social intelligence lies the ability to “mind read” or theory of mind:
this is the ability to infer the
contents (beliefs, desires, intentions) of the mind of other individuals,
predicting behaviour based on these inferences and empathizing with others
states of mind (Baron-Cohen, 1999, 2000, 2006b;
Baron-Cohen, Leslie,& Frith, 1985; Dennett, 1971; Premack & Woodruff,
1978). Mindreading is often seen as a predominantly cognitive ability,
however emotions play a key role in inferring other agent’s content of mind and
reactive adaptively.
Empathizing
has evolved to represent the affective states of others and to react with an
appropriate emotion. The importance of emotions in adaptive social behaviour is
extensive; and they are pivotal in successfully modelling social behaviour.
Relevant here is the somatic marker mechanism suggested by Antonio Damasio (Damasio, 1994, 1996, 1999) and further
elaborated upon by Charlton (Charlton, 2000,
2003; Charlton & McClelland, 1999).
At the
outset, Damasio (Damasio, 1994, 1995, 1999)
makes a distinction between emotions and feelings: Emotions are changes in body
state (and non-conscious brain state to a secondary extent) primed by either
external or internal stimuli. Feelings are the conscious awareness of these
changes in body state (Damasio, 1994, 1995).
Primary emotions are those that are innate and triggered automatically in
certain situations (Charlton, 2000, 2003;
Damasio, 1995). For instance, a
“fear” response can be triggered in the presence of a snake. The somatic
response in this case would be an increase in heart rate, higher frequency of
breathing, dilated pupils etc. This pattern of somatic changes constitutes the
emotion of fear which can prime and initiate behaviour, such as a flight or
fight response. These changes in body states can be observed in most mammals,
however, it’s probably only primates and certainly humans that can be aware of
emotions – that is, experience feelings
(Charlton, 2000)
Secondary
emotions are those emotions triggered by internal events such as remembering an
encounter with a snake. Secondary emotions are induced by cognitive
representations, i.e. internal events that have previously been associated with
a primary emotion. These representations are dispositional in that they include
evaluative information about the object/event priming the emotion in the first
place. Thus, remembering an encounter with a snake can invoke the same changes
in body state as the initial encounter. Secondary emotions can therefore be
seen as being acquired through experience and are built upon the foundations of
primary emotions (Damasio, 1995). In a
nutshell, secondary emotions occur in response to cognitive modelling or
cognitive simulations – such as memories or plans (Charlton, 2000).
Feeling
an emotion is the conscious awareness of this pattern of changes in body state
in relation to the representation that primed these changes. Thus,
representations are juxtaposed with relevant somatic states, i.e. emotions, to
the extent that these representations are associated or marked with a
particular emotion. This juxtaposition of representation and emotion is what
constitutes the somatic marker mechanism (Charlton,
2000; Damasio, 1994).
According
to Damasio (Damasio, 1994, 1996) the
somatic marker mechanism is fundamental to human reasoning and decision making
especially within the social and personal realm. The neurobiological site which
is critical for the somatic marker mechanism to function is the prefrontal
cortex, more specifically the ventro-medial sector (Damasio, 1996). Individuals with damage to this section of the
cortex have strong difficulties making appropriate social decisions, while
still retaining most intellectual capacities (Damasio,
1996).
Ultimately,
a good decision for any organism is one that is advantageous for the
reproductive success and survival of the organism, as well as the quality of
survival (Damasio, 1994, p. 169). Somatic
markers assist and guide the decision making process by modelling outcomes of
decisions through changes in somatic state. A possible bad outcome of a
decision can manifest itself as an immediate negative feeling such as fears,
misery or disgust. The representation of the negative outcome of a given
response option is marked with the unpleasant feeling, allowing the organism to
reject a possible decision from the outset. Thus, in Damasio’s words “somatic
markers are special instances of feelings, generated from secondary emotions.
Those emotions and feelings have been connected, by learning, to predicted
future outcomes of certain scenarios.” (Damasio,
1994, p. 174). The somatic marker mechanism functions as both a warning
and incentive system for possible negative and positive outcomes.
When
somatic markers operate consciously, they can assist in the modelling and
planning of behaviour towards other organisms. By thinking about previous
social encounters and being aware of the emotional /somatic responses that are
evoked through these deliberations, dispositions and intentions of others can
be inferred (Charlton, 2000; Damasio, 1994)
.This means that somatic markers are pivotal in internally modelling social
behaviour.
Representations
of others are linked in working memory with an appropriate feeling, thus
associating own emotional reactions with the representation of others. For
instance, the perception of a rival male can invoke the emotional reaction of
fear. The perceptual representation of
this individual is then marked with the somatic state of fear. At a later point
in time, thinking about this individual, i.e. drawing upon the representation
from long term memory can similarly produce the same emotional reaction.
Inferences about the disposition of the other individual can be modelled upon
the own emotional reaction to the encounter (Charlton,
2000).
The
somatic marker mechanism can be seen as being the underlying neurobiological
mechanism of the theory of mind mechanism and the empathizing system .Where Baron-Cohen
(2005) describes the development and function of these two systems,
Damasio’s somatic marker explain the underlying neurobiological mechanism by
which both dispositions and inferences about another organisms’ mental as well
as affective states
can be made.
Because
human intelligence and consciousness have fundamentally evolved to deal with
the social world, the spontaneous and immediate experience of the environment
is infused by social information. Humans are primed to interpret ambiguous
situation (like the fluttering of leaves) as being caused by agency (Barrett, 2000; Guthrie, 1995) and to reading
social meaning into natural events (Bering, 2002). This tendency to
anthropomorphise the significant environment and to imbue it with social agency
may underlie the evolution of religious beliefs (Charlton,
2002a, 2002b; Guthrie, 1995; Rosenkranz & Charlton, in press).
Empathizing
evolved to focus on people, Systemizing to focus on things
Evolved function of Empathizing – social focus
Empathizing
is based upon the ‘theory of mind’ ability. Theory of mind refers to the
ability, found in some social animals, to infer metal contents such as
dispositions, motivations and intentions in another con-specific.
We
conceptualize Empathizing as the
disposition to apply ‘theory of mind’ cognitive ability – this can be
applied to the social situations for which the ability (presumably) evolved,
and also to understanding the world in general (and not just the social world).
In other words, Empathizing is the spontaneous tendency to focus on people.
Since humans
are social animals, and in line with evolutionary concepts such as the Social
Brain and ‘Machiavellian Intelligence’, we regard social intelligence as
probably deriving from primate ancestry, and closer to the spontaneous form of
human interest than is an interest in things. We therefore regard the highly
Empathizing personality type as underpinned by an evolutionarily more-ancient
personality type than is Systemizing.
In other
words, Empathizing is more fundamental to humans than Systemizing and intrinsic
to the species: Empathizing came before Systemizing. Further, it is
possible that a preference for Systemizing did not evolve in all populations,
and may be weak or absent in some human groups still extant. But in ancestral
hunter gatherer situations – perhaps including pre-modern hominid ancestors –
we would assume that all reproductively successful humans were not just able to
infer theory of mind, but disposed to focus on other humans and their mental
contents: almost everybody in these circumstances was probably a high
Empathizer and it is likely that the the Systemizing trait was low, and that
there may have been few or zero high Systemizers.
Empathizing
– in its evolutionary origins - is therefore personal in its application, being
specifically directed towards actual human relationships. To have an
Empathizing disposition is use this cognitive style (evolved to deal with
humans) as a general model of understanding. Therefore be a high Empathizer is
to see the world through social spectacles: a tendency to focus attention on
social relationships and to understand the world as analogous to social
relationships.
Empathizing
seems to be the natural and spontaneous way for humans to deal-with phenomena
they regard as important: this is seen in the tendency to anthropomorphise
large and important animals, significant places and landscape features,
treasured possessions and so on; and to treat human groups (or modern
institutions) as if they were unified, conscious and intentional organisms.
Re-defining
Systemizing as a preference for focusing on linear sequences of things
The usual
definition of the trait of Systemizing relates to a preference to analyze the
world in terms of the rules which govern systems: such that the
Systemizer is a person who sees the world as composed of systems, and is
interested in categorization and understanding the rules, patterns or
principles that underlie these systems(Baron-Cohen,
2010; Baron-Cohen, Ashwin, Ashwin, Tavassoli,& Chakrabarti, 2009).
However,
while this is an accurate description of the interests of a high Systemizing
personality who also has high general intelligence, it is a potentially
misleading description of the Systemizing trait since it refers to the
understanding of complex systems, that is systems of processes
that are governed by rules.
Yet it
seems plausible that an interest in the abstract understanding of the processes
of complex systems is underpinned (and evolutionarily preceded) by the simpler
abstract task of learning linear
sequences. So in terms of a personality trait, the interest in complex
systems which is measured by Systemizing questionnaires may be considered a more
advanced type of an elementary interest in simpler ‘strings’ of facts,
names, numbers, tasks or procedures.
To create
categorizations, to infer a pattern, and to extract the rules from a system are
in fact higher-level cognitive abilities; possible only to those of relatively
high general intelligence. Abstraction of rules is, indeed, one of the main
attributes of ‘g’ which is measured in standard IQ tests: for example in
supplying the next member of a number series, or establishing group membership,
or performing a task like Raven’s matrices (Deary,
2001; Gottfredson, 2005; Jensen, 1998).Those of low general intelligence
are poor at these tasks (which is why they are used to measure IQ), and this
implies that a focus on understanding the rules of systems is a high-level
definition of Systemizing.
Therefore,
while inferring categories, patterns and rules certainly count as Systemizing,
we would favour a more basic and less cognitively-advanced basis for defining
systematizing: that the Systemizing trait is seen at its most basic in trying
to learn linear sequences of abstract facts or actions.
The two
main aspects of Systemizing, we suggest, relate to the nature of content
which is not-social i.e. abstract; and to the content being understood
in terms of linear sequences of facts. Therefore Systemizing relates to:
→ Abstract phenomena (things not people)
→ Of a specific identity (these particular things)
→ In a specific order (in this order, or categorized thus)
A modern
example of the Systemizing preference, would be the kind of crazes and
‘obsessions’ which are characteristic of people on the autism spectrum or with
Asperger’s syndrome: learning lists of names and numbers from the telephone
directory, or certain types of dates, or pictures make by highly-literal
copying, or learning all the facts on a non-social themes such as automobile
performance or the performance of a sports team, or literal recollection of
sequences from favourite TV shows or passages from books, or hobbies involving
collecting and arranging – such as stamps, cards or train-spotting.
These and
other pastimes such as crossword or other puzzles, or some types of computer
games, are often about assembling sequences of correct facts or procedures
(united by theme or category) in a correct and specific order or pattern – yet
these facts or procedures may not have any rule-based ‘systemic’ structure.
Typically, one cannot learn these kinds of activity by learning and applying rules;
rather, the activity consists in performing exact sequences of correct
responses on specific material.
Interestingly,
an explanation of Systemizing in terms of the disposition to focus upon
‘close-up’ consideration of abstract linear sequences, bears striking
similarities with the concept of left cerebral hemisphere dominance as
described in Iain McGilchrist’s The
master and his emissary concerning autistic traits and ‘attention to
detail’ (Baron-Cohen et al., 2011; McGilchrist,
2009); although at the same time McGilchrist’s evidence and argument
renders implausible any direct equation of left hemisphere with male, right
with female. The argument is complex and we flag it here as a matter deserving
further and detailed consideration.
Systemizing and psychological
neoteny
Indeed,
this kind of behaviour focused on linear sequence of abstract knowledge is
characteristic of children; for instance when they insist on a fairy story
being told with exactly the same words and details. Many pre-adolescent boys,
in particular, have periodic ‘crazes’ on various subjects (aircraft, trains, a
type of book, a type of construction model, a particular sport) about which
theme they voraciously learn everything they can manage.
These
pre-adolescent boy’s crazes are typically not focused on people nor on
social relations, nor are they focused on rule-based understanding; rather they
are fact-based, convergent activities involving listing, collecting,
categorizing, memorizing – based on learning sequences and patterns but not
often complex or dynamic ‘systems’.
This
similarity between pre-adolescent boys and high Systemizing men does not tell
us why high trait Systemizing may have evolved – does not tell us how
high Systemizing may have improved differential reproductive success in our
ancestors - but it may suggest how high Systemizing evolved: by perpetuation
of pre-adult behaviour into sexual maturity. In other words high
Systemizing trait in adults may be a neotenous phenomenon.
(Neoteny
is one type of the more general class of ‘heterochrony’in which evolutionary
change is brought about by alterations in the timing of developmental events (Horder, 2001)
And this
may provide a clue to the proximate mechanism for the evolution of higher
levels of trait Systemizing. Natural selection usually works by quantitative
modification or amplification of some already-existing trait (as when a hand,
or an arm, evolves into a wing in a bat, or a bird; or when a neck, or a nose,
become lengthened in a giraffe, or an elephant). In humans, the evolution of
the high levels of Systemizing seen in modern people suggests that there was
some original trait which underwent evolutionary adaptation.
In other
words; if neoteny – or something similar – was the proximate mechanism via
which natural selection led to Systemizing, then we need to consider the trait
which was present in immature humans that may have provided the basis for the
evolution of adult Systemizing.
E-S reciprocity and sex
differentials generated by selection pressure from economic factors
What are
the main observations concerning E and S which an evolutionary hypothesis must
explain? One is the reciprocity between Empathizing and Systemizing –
that when one is high the other is usually low.
In a
sense, reciprocity is an intrinsic property of some personality traits: one
cannot be both highly extravert and highly introverted, cannot be both highly
neurotic and very stable. Similarly, one cannot be fascinated by social
relationships such as to spend most of one’s time and energy on that matter,
and at the same time fascinated by learning about abstract facts and
figures and systems so as to spent most of one’s time and energy on that
matter as well.
Most
strong personality traits can, in principle, alternate in dominance over time
and with circumstance – but they cannot dominate simultaneously. So it is an
intrinsic property of E-S being descriptive of a personality trait that
the predisposition towards one extreme of the trait is itself a
predisposition away-from the other extreme.
However,
the E-S personality traits have been persistently observed as different, on
average, between men and women. And most of the most highly empathic people are
women, while most high systemisers are men. This observation invites an
evolutionary explanation.
We
suggest that the ultimate (evolutionary) cause of sex differentials in E-S lies
in the ancestral sexual division of labour among humans; men and women
having different characteristic roles: women focused child care and food
gathering and preparation, men focused on whatever other tasks require doing:
e.g. hunting, fighting, crafts(Lee & Daly,
1999; Lee & DeVore, 1968; Ridley, 1997).
Specifically,
we regard Empathizing as a baseline state common to ancestral men and women,
and Systemizing as having been selected-for at a later stage of human
evolution, primarily among men due to
the ancestral economic division of labour, and the economic benefits of having
some men who are high Systemizers. We assume that there were significant
material rewards for those men who were both able and willing to perform
Systemizing tasks, and that these extra resources would have enhanced the
survival of the offspring of successful Systemizers.
Evolution of the Systemizing
trait
To
recapitulate, the Empathizing trait refers to theory of mind abilities, which
would be expected to be more evolutionarily ancient than the Systemizing trait,
since they are found in non-human primates. Therefore a disposition towards
Empathizing (theory of mind) are hypothesized to be a feature of pre-human
primate and ancestral hunter-gatherer societies. We believe that Systemizing
came later in human evolutionary history, and was an ability and disposition
that (in a sense) displaced pre-existing Empathizing in some men.
By
contrast, it is hard to see any need for, or evidence for, high levels of
Systemizing trait in ancestral-type hunter gatherer societies, and it is hard
to imagine a plausible benefit for a personality type which is characterized by
high Systemizing. Ancestral hunter gatherers were (it is assumed) well-equipped
by natural selection to deal with most of the non-personal/ ‘thing’-related
problems they would encounter, since they had lived in the same type of
environment for up to hundreds of generations. The social brain perspective
suggests that the most cognitively-complex tasks our ancestors confronted were
related to understanding, predicting and manipulating human social interactions
(Byrne & Whiten, 1988). And for these
problems, humans were prepared by their theory of mind abilities, and the
‘Empathizing’ personality was motivated to apply theory of mind abilities in
relating to the world.
Furthermore,
ancestral hunter gatherers were generalists: apart from a sexual
division of labour, essentially all women were involved in gathering and child
care, all men were warriors and hunters. Any other activities needed to be
fitted-around these requirements, but because the usual group size was small
(probably around 15-35 including both the young and the old) there was only a
little scope for specialization of function except in terms of sex and age (Charlton, 2000; Lee & Daly, 1999)
Systemizing
abilities and interests seems likely to be most beneficial in
post-agricultural, more complex, less ‘natural’ human societies. Indeed,
agricultural societies are usually characterized by some degree of economic
specialization - especially among men (Woodburn,
1982). This is necessary because of the greater need for learned
knowledge and technology – agriculture is itself a specialist expert activity
requiring not just invention but significant preservation and
inter-generational transmission of knowledge (which is why it was not invented
as a stable and continuing social form until the past 10-15,000 years)
The
evolution of Systemizing can therefore be seen in the context of life history (Rushton, 1985). Woodley (2011) sees ancestral hunter gatherer societies as
characterized by a relatively fast life
history – with high fertility, rapid maturation of offspring and early
maturity – and this leading to an un-specialized type of human – with a narrow
range or ‘manifold’ of abilities. This situation may be associated with strong sexual
selection – men investing on average little in their offspring but competing
for multiple promiscuous matings (with uncertain paternity); presumably men
would tend toward early maturity, high vigour and physical prowess, but a short
life and a mainly social intelligence (e.g. men being charming rather than
Systemizing).
By
contrast, as agriculture emerged, and population density increased; it is
probable that life history was slowed due to greater competition between humans
(Woodley, 2011) In such a situation, men
especially would seek a niche in which they could excel, and this would
be associated with slower and later maturation – and a wider range (or
manifold) of abilities between individuals - which meant that some people were
better at one thing while other people were expert at different things. The
trend would be towards lower fertility but higher level of parental investment
per offspring – and the father contributing economic investment to their
offspring (about which they would need have had a high degree of certainty of
paternity for this behaviour to be adaptive; Wilson
and Daly (1992), Charlton and McClelland
(1999).
In
ancestral ‘simple’ hunter gatherer societies there were probably a few tasks
which focused on dealing with ‘things’ and where a personality preference for
such tasks might be adaptive: problems such as navigating across a desert, manufacturing a spear thrower or stone axe,
or preparing poison for a bow and arrow. Typically such jobs require (in
pre-literate societies) learning and precisely remembering an exact sequence of steps.
But such
tasks are far more numerous, and more important, in agricultural societies
where there is more technology, and where farming and the preparation and
storage of food must be learned and repeated exactly year after year(Woodburn, 1982) . Such societies also
typically develop specialists in religious ritual (priests) and in various
crafts – and craft expertise in particular becomes absolutely essential to the
survival of societies(Ingold, 2000; Ridley,
1997) .
Yet such
crafts must be devised, remembered, and transmitted between generations. Our
assumption is that it was this kind of selection pressure in agricultural
societies which led to the evolution of high levels of Systemizing seen in some
members of modern populations.
Systemizing
was therefore a kind of expert ability and disposition; indeed
Systemizing was exactly the trait that would enable expertise to
develop; because expertise was (we infer) mostly a matter of learning and
memorizing accurately precise sequential facts and procedures. Thus the development of expertise is only
partly about ability to perform a type of task – equally (or more) important is
the personality which is motivated to do such tasks.
In other
words, we suggest that until the development of agriculture, humans were
originally towards the Empathizing end of the trait and that sexual
differentiation was probably very limited; that the characteristic observed
modern pattern of E-S is primarily a product of economic selection pressures
following the development of agriculture; and furthermore that the sexual
differentials in E-S are a consequence of historical differences in economic
selection pressures as they operated on men and women since all ancient human
societies display very considerable sexual specialization in terms of economic
roles (Indeed, humans are among very few species exhibiting economic sex
specialization;(Ridley, 1997).
We
suggest, therefore, that the primary evolutionary cause of the range and reciprocity
of E-S and also the higher average levels of S in men, was the sexual division
of labour in a context of post-hunter gather economic systems. One implication
is that men and women in hunter gatherer societies were probably more similar
in the E-S dimension than are men and women in agricultural and
post-agricultural societies (a prediction that may be partially-testable in
modern descendants of these populations).
Sexual selection
Personality
clearly affects sexual attractiveness, and may therefore be subject to sexual
selection. On the one hand, common sense, personal observation and theoretical
considerations suggest that, on average, women do not find the highly
Systemizing personality (with its preference for things rather than people) to
be (of itself) sexually attractive in men. On the other hand, female sexual
preferences are not necessarily an important factor in determining sexual or
marriage partners. Many human societies have not allowed much scope for
individual female choice of sexual or marriage partners – for instance when
young women are allocated to husbands as when marriages are arranged by
parents, religious leaders or the wider community (Wilson & Daly, 1992). And in these societies, sexual
selection, most often female choice, may be greatly attenuated or
insignificant.
Individual
sexual choice seems, in particular, to be very limited in most stable
agricultural societies – and it is our assumption that it was precisely these
stable agricultural societies in which the Systemizing trait is likely to have
arisen and been amplified in men.
A further
factor is that one of the most powerful factors affecting female sexual
preference is male status. Insofar as a high Systemizing trait leads
to higher status in a man, then it may be indirectly sexually
attractive – unattractive in itself, but associated with a higher status that is
attractive (Buss, 1995; Symons, 1980).
But – at
the first level of analysis – we suggest that Systemizing trait may have arisen
despite sexual selection, rather than because of it.
*
If the
Systemizing trait is probably (on average) unattractive to women, this suggests
that - when women are allowed to choose freely, sexual selection probably works
to reduce or eliminate the Systemizing trait. This would imply that – under
modern conditions of independent femal choice of sexual and marriage partners,
Systemizing would be under a negative selection pressure; and that this aspect
of male personality may well be experiencing a ‘selective sweep’ in which the
representation of the trait in the gene pool will be changing from one
equilibrium towards another (Miller, 2010).
Another
aspect is that a highly Systemizing disposition would presumably (like all
personality traits) be substantially inherited by female children as well as
male children – even when there are sex differentials (Miller, 2000). So that highly Systemizing trait women would become
more common, as well as highly Systemizing men – simply as a by-product of the
economic selection pressure on men.
Then,
since Systemizing reflects a person’s interests, and shared interest may be a
factor in mate choice; it would be expected that highly Systemizing women would
tend to regard highly Systemizing men as relatively more attractive –
especially if the woman was expecting to spend a lot of time with her husband.
This would be a form of assortative mating, whereby sexual partners are
chosen on the basis of similarity (Miller, 2009) . And assortative mating between high
Systemizers could plausibly be a mechanism by which ultra-high
Systemizing might become a feature of populations – especially in men
(Baron-Cohen, 2006). Therefore this is a plausible mechanism for the emergence
of Asperger syndrome at a high frequency and severity – as a by-product of high
Systemizing women choosing high systematizing men as partners.
Summary
Our
hypotheses concerning the evolution of Empathizing can briefly be summarized:
1.
The baseline state is that (since humans are social animals) ancestral human
hunter gatherers are assumed to be high Empathizers: more interested in people
than in things.
2.
Economic changes, especially related to the development of agriculture, and
also other technologically dependent societies (requiring complex tools,
weapons, equipment, housing etc) mean that it becomes useful for some men to
become more interested in things than in people, as a motivation for them to
learn and practice socially vital skills.
3.
This selection pressure applies mainly to men since in the sexual division of
labour it is typically men’s role to perform such tasks.
4.
The Systemizing trait is amplified by natural selection in men – perhaps by a
neotenous mechanism where childhood traits are retained into adulthood. High
Systemizers emerge: men who are spontaneously more interested in things than in
people.
5.
High Systemizers are rewarded for their socially vital work by high status (and
supported with resources).
6.
Social arrangements develop (or already exist) that allocate women of high
reproductive potential (young and healthy) to successful high Systemizers (for
example by arranged marriages, dowry payments or bride price settlements) –
these mechanism suppress or overcome the sexual selection mechanism by which
women choose sexual partners or husbands who are Empathizers.
7.
The marriages of economically successful high Systemizing men will experience
greater-than-average reproductive success (with more surviving and viable
offspring due to differentially increased access to economic resources such as
food, shelter, technologies etc.) – thus amplifying the representation of genes
that cause high systematizing in the population.
Predictions
The
theory has a number of testable predictions:
Systemizing
may be undergoing (in developed societies) on the one hand assortative mating
which amplifies the number of very high Systemizers (Baron-Cohen, 2006a); and on the other hand a selective sweep that
is reducing the average level of S, due to the greater operation of sexual
selection in the form of female sexual choice.
The male
female difference in E- and S may have been less in hunter gather
societies than in agricultural or modern
societies – and this may be measurable in the societies which have recently
been hunter gatherers and have not yet experienced many generation of the
selection effects of complex societies.
The
theoretical model suggests possible methods of measuring Systemizing and
Empathizing by developing instruments that quantify people’s spontaneous
preferences as expressed in choices between focusing on either on people or else things.
References
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