PSYC18—CHAPTER TWO: EVOLUTION OF EMOTIONS
Among the evidence that Darwin advanced for his theory of evolution was the similarity of human emotional
expressions to those of other animals.
Elements of an EvolutionaryApproach
● Darwin described evolution in terms of three processes:
➢ Superabundance: Animals and plants produce more offspring that a necessary merelt to reproduce
➢ Variation: Each offspring is somewhat different to others, and differences are passed on by heredity
➢ Selection: Those characteristics that allow better adaptation t the environment are selected because they
enable survival and hence are passed on.
● At the core of natural selection are selection pressures (features of the physical and social environment in which
humans evolved that determined whether or not they survived and repFor example, food and water.
● Two kinds of sexual selection pressures determine who reproduces.
➢ Intersexual competition refers to the process by which one sex selects specific kinds of traits in the other sex
(e.g. women and men prefer mates of good character).
➢ Intrasexual competition is competition for mates within a sex(e.g. stags engage in battle)
● Nesse argued that fitness—the likelihood of surviving and reproducing successfully is increased for those who are
preferred as sexual partners.
● Adaptations are genetically based traits that allow the organism to cope well with specific selection pressures, and to
survive and reproduce (e.g. taste buds adapted to recognize sweet taste as nutritionally beneficial).
● Humans prefer symmetrical faces as mates (asymmetrical faces related to parasitical diseases).
● We also prefer beautiful faces because we infer that good faces=good character. Tsukiura and Cabeza used fMRI
scans and found that activity in the medial orbitofrontal cortex, a region involved in the processing of rewards was
increased by both ratings of attractiveness and goodness of an action. Whereas the activity in the insular cortex
decreased with the two.
● Since women are child-bearers, they place more emphasis on finding a mate with “resources” (higher-status males),
men are attracted to women with full lips, hourglass figure and youthful skin (their goal is to pass on genes).
● Men are usually mentally aroused when they are physiologically aroused.
● Our responses to baby-like cues (e.g. stuffed animals) ensure that parents help their offspring reach the age of
viability. Our love for children overpowers the costs of children (due to natural selection).
● Some human traits (e.g. snoring, leg jiggling) serve no evolutionary function, they are more like by-products.
● Evolution is a tinkerer and often endows old anatomical and behavioral features with new functions. Atrait that
acquires a new function is called an exapation.
● Facial expressions in humans were developed from reflexes. Animals have a reflex in which they flatten their ears
when started/when they approach another member of their species. Its original function was to protect the ear, but
now it serves as being easily recognizable in others (e.g. angry dogs flatten ears). Raising the eyebrows serve the
same function in humans and derive from the same movement (we raise eyebrows when meeting someone new).
Natural Design for Gene Replication
● Emotions are adaptations hat help humans meet selection pressures (related to reproduction, survival, and social
● Humans have 100 trillion cells, 23 pairs of inherited chromosomes, 25000 genes.
● Our genes = NOT in our service; our genes pass themselves on to the next generation: they reproduce themselves.
● Genes are technically “immortal” but they can’t survive on their own (they need a body/plant).
● Our socially based adaptation (which helps the genes survive) involves us being decent/altruistic to each other.
● Emotions allow our genes to program us (e.g. we’re emotionally drawn to nutritious food and interested in sex).
● Darwin, however, suggested that the programming of genes was absolute (e.g. jumping back from fear in response to
a snake=modern human emotions derive from ancestors or males reflex-like physiological arousal to attractive
females). Thankfully, our human cultural purposes become more important than genes. ● Therefore, our gene programming occurs on a range (from instinctual to human social/cultural).
● Unconscious effects of gene programming can affect emotional biases, impulses and instinctual urges.
The Social Motivations and OneAntisocial Motivation
The social motivations and the antisocial motivation can be thought of as adaptations, selected for during
● John Bowlby defined the psychological attachment accompaniment of the physiological fact that babies are nurtured
with milk as attachment. He derived this theory from Konrad Lorenz’s theory of imprinting: shortly after hatching
form their eggs, goslings learn to recognize and follow the first largish, moving, sound-making object in their
● When geese imprinting on Lorenz himself, they did not recognize other geese; they made social signals to him.
● Attachment=human form of imprinting, it’s function is to protect and care for the infant.
● Bowlby also proposed the idea of the mother as a secure base (infants can explore new environment with its mother
present: the baby can retreat to her if necessary and she keeps a watchful eye open). The mother as a secure base
continues until adolescence.
● Trust=confidence that one is, and continues to be safe. Emphasized by attachment theory.
● MaryAinsworth made a list of attachment behaviors infants did only with mother (pg 39, table 2.2).
● Bowlby proposed love/attachment during infancy as important for emotional development. Attachment relationship
creates a template for all later intimate relationships, and he coined the term affectional bonds.
● Darwin co-related adult sexual caressing with early infant holding/being held.
● Humans live in hierarchal world.
● Another social motivation is assertion or power. Assertion is the desire to move up in the hierarchy and to resist
challenges from those who would move us downward. Shame=having one’s social status diminished.
● Power is carefully regulated (by the law, by responsibilities etc.).
● Third social motivation is affiliation or affection.
● Fox and Davidson found that babies seeing their mothers approaching with open arms showed joy and an activation of
the left side f the frontal cortex. The system activated is part of affiliation./ By contrast, distress/separation from a
caregiver involved not so much a reduction of such activation, but changes in a separate system, on the right side of
the cortex.Although attachment occurs in all primates, only some species show affectional bonds.
● McDonald and Goldberg et al. hypothesized that the separate systems can be differently prioritized in different
cultures. People express more emotions that are communal and that have a positive reward aspect.
● Whereas assertion is the motivation to compete, affiliation is the motivation to co-operate.
● Djikik and Oatley suggest that evolved sex motivation becomes, combined with other evolved motivations, a state in
which sexual partners can bestow love upon one another.
● Male Provisioning Hypothesis: Lovejoy argued that critical evolutionary steps taken when humans started to walk
upright (and thus could not cling to their mothers as ape babies do and thus had to devote more resources to them). At
the same time, males starting playing a role in child rearing and thus moved away from promiscuity. In humans long-
lasting sexual relationships began known as pair-bonding. Thus, affection=evolutionarily beneficial.