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This
is a summary of a lecture given on 22 Oct 2005 to 20 psychiatrists in Leichhardt
Sydney as the dinner lecture component of a half-day inaugural seminar
entitled "Why Evolutionary Psychiatry" sponsored by the Evolutionary
Psychiatry Special Interest Group, St John of God Health Services,
AstraZeneca and Wyeth. ContentsWhy use a Darwinian lens in Psychiatry?
Through the Darwinian looking glass…
Normal minds – evolutionary psychology
Evolutionary Classifications in Psychiatry
Why use a Darwinian lens in Psychiatry?
Why isn't the mind better designed?
DALYs Western Females 18-45 yo (WHO)
Victorian Burden of Disease Study: Incident YLD rates per 1000 population by mental disorder
Why isn't the mind better designed?
The Paradigmatic Failure of Psychiatry
DSM?
Why isn't the mind better designed?
Two kinds of explanation essential
Reductionist approaches miss half the story
The Four Areas of Biology
What might evolutionary approaches add?
Through the Darwinian looking glass…
What are brains for?
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…all the corporeal & mental organs …have been developed through natural selection, or the survival of the fittest, together with use or habit...
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We are built as gene (replication) machines …
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…our brains have evolved to make decisions that enhance reproductive success |
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Refers to differential survival of traits | |
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Genetic variations in traits affect reproductive success | |
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An individual may acquire a propensity that makes him better adapted than his peers in surviving & passing on genes | |
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Over generations, that attribute will become established as a standard component in the species genome |
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NS shapes bodies to maximise reproduction at the expense of health | |
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NS shapes traits to ensure transmission of genes – too bad for the species | |
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Genetic disease results mainly from quirks that were harmless in the Paleolithic | |
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NS continues after menopause via kin selection |

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Food acquisition | |
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Cooperation | |
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Inclusive fitness | |
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Inclusive fitness | |
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Tribal bonding | |
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Reciprocal altruism | |
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Conflict over resources | |
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Self defence |
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An act or signal that gives up options to influence someone’s behaviour by changing incentives or expectations | |||
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It changes behaviour by giving up options and changing beliefs | |||
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Lots of examples, main distinction is how they are enforced
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Pleasurable sensations … stimulate the whole system to increased action. | |||
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Hence it has come to pass that most or all sentient beings have been developed in such a manner, through natural selection, that pleasurable sensations serve as their habitual guides. | |||
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But pain or suffering… lessens the power of action, yet is well adapted to make a creature guard itself against any great or sudden evil. | |||
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…if long continued, causes depression
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“Adaptations” shaped by Natural Selection | |
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Each emotion is a specialised state that adjusts cognition, physiology, subjective experience & behaviour so that the organism can respond effectively in a particular kind of situation | |
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Positive & negative emotions are derived from the two types of basic arousal |
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Our ancestors faced many more kinds of threats than opportunities, as reflected by the fact that twice as many words describe negative as positive emotions! | |||
The emotions were “designed not to promote the happiness & survival of the individual, but to favour maximum transmission of the controlling genes.”
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"People, like all other
organisms, are not evolved to maximise health, wealth, happiness or any
other trait – but to have descendants, which is the continuation of
life."
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Sociobiology/Behavioural Ecology | |
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Ethological Models | |
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Evo Psych (Cognitive) Models | |
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Psychiatric Models | |
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Neuroscientific models | |
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Archaeological Models | |
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Anthropological Models Philosophical Models |
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Blank slate / “Cupboard love” theory = Behaviour is the result of classical conditioning | |
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General purpose computer | |
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Learning | |
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Culture |
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In the distant future I see open fields for far more important researches. Psychology will be based on a new foundation, that of the necessary acquirement of each mental power and capacity by gradation."
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“Human nature” refers to the accumulated specialized neural circuits that are common to every member of a species and are the product of that species' evolutionary history | |||
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Our modern skulls house a stone age mind |
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The view of the mind as containing a whole suite of modular psychological adaptations | |||
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Each blade represents pre-programmed algorithms sensitise the organism to monitor specific situations | |||
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biases to learn certain behavioural responses |
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Social cognition: information processing that contributes to the correct perception of dispositions & intentions of other individuals | |||
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Theory-of-Mind: inferring mental states of others
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Group cooperation (reciprocal altruism) requires cheater detection algorithms
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The Social Brain Hypothesis: Vol. of non-visual neocortex correlates with group size & length of juvenile period
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All perform worse on ToM tasks:
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Natural selection has equipped us with lifespan-specific, context-sensitive archetypal propensities to navigate biosocial imperatives that facilitate inclusive fitness. | |||
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Genes are conveyers of potential for species-characteristic behaviours, rather than rigid determinants of social behaviour.
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Human “instinct”
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“Collective unconscious”
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Mother-infant instinct
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Defense (fight or flight)
Attachment
Dominance-striving
Reproduction
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(Gardiner, 1988) |
The stranger archetype
The affiliation and bonding archetype
The hierarchical ranking dominance-submission archetype
The courtship & mating archetype
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(Stevens & Price, 2000) |
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Harm from strange humans --> Stranger anxiety | |||
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Separation from carer --> Separation anxiety | |||
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Threats to status/group membership --> Social anxiety | |||
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Socially unaccepted impulses --> Obsessive self-doubt | |||
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Lack of food or other resources --> Obsessive hoarding | |||
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Getting sick --> Hypochondriasis/Obsessive cleanliness | |||
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Dangerous small animals --> Small animal phobias | |||
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Potential attack to family members --> General anxiety | |||
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Imminent attack by predator --> Panic | |||
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Environment in which attack is likely --> Agoraphobia
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… to motivate to urgent action | |||
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for survival | |||
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…to respond to Danger… | |||
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…with Fight … | |||
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… Or Flight …
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Anxiety is a useful defence | |
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…but it uses extra calories, makes us less fit for everyday activities & damages tissues | |
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So why is it so readily triggered? | |
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Because the cost of getting killed even once is enormously higher than the cost of responding to 100 false alarms |
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Loss of attachment – carer, mate (Bowlby, 1969) | |||||||||||||
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Loss of rank – social status (Stevens & Price, 2000) | |||||||||||||
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Loss of resources (Nesse, 2000)
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Communicate (Darwin, 1872) need for help | |
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Signal yielding in hierarchy conflict | |
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Disengage from unreachable goals | |
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Regulate patterns of investment |
(Nesse, AGP, 2000)
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Social Competition Hypothesis of Depression
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Loss of resource holding potential (self esteem) can cause depression
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Serotonin (5HT) in a-male (highest ranking) vervet monkeys 2x other males | |||
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When lost their position: appeared depressed (huddled, rocked, refused food) & dropped 5HT levels | |||
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Depressed behaviour prevented by Prozac, which raised 5HT | |||
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If removed a-male & gave Prozac to random male, that male became a every time
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Primary brain abnormalities
Environmental trauma or uniqueness
Byproducts (Adaptive but distressing)
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(adapted from Nesse RM, 1991) |
1. Disorders of Malfunction
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Differentiation - Mental disorders that result from localised (modular) brain malfunction due to genetic vulnerability or injuries of the developing central nervous system | |
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Integration - Mental disorders that result from NON-localised brain malfunction due to genetic vulnerability or injuries of the developing central nervous system |
2. Disorders of Dysfunction - Mental disorders that result from dysregulation of adaptive responses leading to failure to achieve specific biosocial goals of the entire organism
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Environmental uniqueness | |
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Maladaptive memes |
3. Disorders of Sociability - Mental disorders due to behaviours causing severe subjective or objective distress and negative/harmful social consequences
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(adapted from Nesse & Williams, 1996; Nesse R, 1999) |