Proximate vs. Ultimate Explanations

Quick aside:

-the first few lectures have been a bit “atypical” (setting stage)-soon we will get to the “content”-talks will use game theory to address puzzles-homeworks and discussions will begin

Panning out:

• First class: motivated/gave thesis• Second class: illustrative example of the power of game theory, and how to treat as a

science• Third class: evidence for KEY assumption needed for thesis: we learn• Today: will discuss crucial distinction between “proximate explanations” and “ultimate

explanations,” and discuss why ultimate explanations important(to give better impression of scope and utility of this class—ultimate explanations)

• Next class: basics of game theory• Then first application: hawk dove, animal territoriality and human rights• More similar examples and models to follow

Homeworks will start next week…discussion sections will start next week (albeit backlogged)

Let’s illustrate the difference between “ proximate explanations” and “ultimate explanations” with a few example:

How do animals usually get 50-50 sex ratios?

-x,y chromosome in mammals-flipped in birds-temperature in some turtles…

Why? -Fisher/Nash!

Ultimate

Proximate

Notice two different explanations are not “in contradiction.” One does not “rule out the other”

Just different “levels of analysis”

More examples…

Why do pregnant Fijians not eat seafood?

-They believe gods will smite them

Why? -Because raw fish is dangerous for fetus

Ultimate

Proximate

Why do Indians eat spicier food than Norwegians?

-Frequent exposure to capsicum numbs Indian’s spice receptors

Why? -Because more pathogens in hotter climate of India

Ultimate

Proximate

Ultimate = “functional” explanation I.e. Why is this the outcome of an evolutionary/learning process?

Proximate = ANY other explanationE.g., What is the physiological/psychological mechanism by which this functional goal is achieved?

The prox/ult distinction is widely employed by biologists and psychologists

In “evolutionary psychology”:

Why do we prefer to date individuals with more symmetric faces?

Proximate (psychological): because we find symmetric faces beautiful

Ultimate (evolutionary): symmetry signals healthy development

In biology:

Why does a mother drop worm when nestling pecks beak.

Proximate: any touching of beak while worm in mouth causes release.

Ultimate: “kin selection”

In this class, like evolutionary psychology and evolutionary biology class, we care about ultimate explanations.

But why are ultimate explanations relevant?

- Suggests moderators! - Suggests prescriptions! - Suggests generality!- Prevents nonsequitors!

Let’s give two a few concrete examples from evolutionary psychology where ultimate proved quite useful…

Example: Gambler’s Fallacy

• Why do people get addicted to gambling?• Proximate theories: for the adrenaline, to be

social, to solve money problems• Treatments: go rock climbing, join a club, talk to

a credit counselor

Source: http://www.helpguide.org/mental/gambling_addiction.php

Example: Gambler’s Fallacy

• What about ultimate explanations?• The Gambler’s Fallacy. We intuitively expect a

gamble to be correlated with a recent gamble• Worked for millennia for hunter gatherers and

became hard-wired in the mind—but it’s not true in casinos

• Novel prescription: take long breaks between strings of bets to minimize the inferred correlation

Source: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3576625/

Example: “Chemical Imbalance”

• Antidepressant use is widespread• Used by 13.6 percent of American whites over

11. (source)

• Such treatments can be motivated by a “chemical imbalance” theory of mental illness

Example: “Chemical Imbalance”

• Ad: “Zoloft works to correct this imbalance.”

Example: “Chemical Imbalance”

• But “chemical imbalance” is proximate.• Why do we get this chemical imbalance in the

first place?– Work environment, academic achievement,

relationships…

Example: “Chemical Imbalance”

• What about ultimate/functional explanations?• Ruminations: fixating on one problem. Hallmark

of depression.• “People who get more depressed while they are

working on complex problems in an intelligence test tend to score higher on the test.” (source)

• Novel prediction: depression may be designed to help people solve the problem that caused it. Medicating may slow progress.

Note value of ultimate: without it, would medicate without recognizing potential for prolonging problem

We will develop similar such prescriptions throughout our class!

In general, without knowing ultimate, we might miss out on key moderators…

Example: The Major Histocompatibility Complex

• Facts: Major Histocompatibility Complex genes are central to immunity and codominantly expressed (both mom and dad’s genes present in offspring).

• A more diverse set of MHC genes engenders a more pathogen-resistant individual.

Example: The Major Histocompatibility Complex

• Thus, organisms should prefer mates with divergent MHCs, which increases the chances that their progeny will reproduce

• Studies on primates, birds, and mice all demonstrate this preference

• How do humans tell who has divergent MHC?– Women find odor of some men more attractive than

others– They rate the odors of MHC-dissimilar men as more

pleasant!

Example: The Major Histocompatibility Complex

• Identified new moderator: odor • And… can generate new predictions– Preference for odor will vary with fertility– Bears out in the data

And now for an example where ultimate has taught us “generality”…

• Males are less “choosy” and more competitive than females

• Trivers explains how this results from fact that males generally invest less in parenting

sex difference in choosiness/competitiveness should NOT hold in species (e.g. seahorses) where males do more parenting!

And for an example where understanding ultimate prevents non-sequitors…

Might conclude (as Marx did) that just as bees can sacrifice for good of the group, so too can human’s be trained to sacrifice for the good of the group.

But ultimate tells us bees sacrifice for good of colony (arguably) because closer related to other colony members than offspring…

Which isn’t true in human societies, so not clear can be trained to be as prosocial as bees.

Marx’s nonsequitor was (arguably) quite costly…

So ultimate explanations can be QUITE useful…

In this class we will be focusing on ultimate explanations that involve game theory for our preferences/ideologies!

(not behavior; not asocial)

Like spices/raw fish and symmetry but unlike sex ratios, we will be studying preferences/beliefs NOT simply “behaviors.”

Also notice:

Unlike spices/raw fish and symmetry but like sex ratios, the explanation will involve a “game” (where “payoffs” depend on own choice+others choices)

At the end of the day, we will gain a much deeper understanding of our quirky preferences/ideologies!