8 - Choice Behavior

“a decision is a deliberative process that results in the commitment to a categorical proposition”

yes, e.g when deciding on sensory input

‘did i hear p or d?’

useful to quantify perceptual decisions in humans

Experiment:

subjects have to decide if a color is red or blue (its slightly varying)

• sensations of colors are distributed on overlapping Gaussians —> overlapping part hard to distinguish —> can be incorrect answer

• ideal observer —> ratio of false positives and false negatives would be 1:1

• this ratio can change based on rewards and penalities (You get money if you correctly identify blue —> more false positives. You get money if you correctly identify red —> more false negatives)

classification of sounds as phonemes

—> adults usually have prototype phoneme

—> sounds will be compared to prototypes and the most likely one is the vocale we decide on

person from area with phoneme rich language can more easily learn new languages (easier to distinguish)

often studied with visual tasks

• monkey has to keep fixation

• more dots to one random dot in specific direction

  —> animal has to decide for direction —> reward

neurons encode decisions by their spike rate

—> find right spike-rate during decision-making process

• Ramping Model: individual spike rates drift from baseline to upper or lower bound

• Step Model: individual cells make single activity step to upper or lower bound

a theroretical person

• always makes same rational decisions

• maximizes utility

• has absolute preferences, never changing (of e.g comparison)

Homo sapiens has relative preferences

• confused by uncertainty and risk

• shows framing effect and endowment effect

• has difficulty to assess value in future

Homo oeconomicus has absolute perferences

• never changing, regardless of comparison

• always makes same rational decision

Confronted with gains:

• Fear of disappointment

  when confronted with moderate chance of success —> risk averse

• Hope of large gain

  when small chance of success —> risk seeking

Confronted with losses:

• Hope to avoid loss

  when confronted with small chance of not losing —> risk seeking

• Fear of large loss

  when small chance of losing —> risk averse

framing = putting a decision into specific context

• people can be manipulated into picking specific option

  • if you ask a way that stresses potential gains —> risk avers

  • if you stress losses —> risk seeking

—> often used in real life (commercials)

—> people demand higher price to sell an object, than willing to pay for same object

possession of objects increases its value for owner

rewards that occur in future have risk of not being collected

—> value discounted

humans prefer immeditate reward vs better options with delayed reward

humans see own behavior as logically explained in situation

behavior of others explained by their character

1. Intuitive

   • fast

   • works at non-conscious, intuitive level

   • uses parallel processing

   • independent of intelligence and attention

   • everyday decisions

2. Rational

   • slow

   • works at conscious, explicit level

   • uses sequential processing

   • depends on intelligence and attention

   • complex decisions

Dorsolateral prefrontal cortex

• Ventrolateral orbitofrontal cortex

• Lateral orbitofrontal cortex

• Intraparietal cortex

• Supplementary motor area

• Presupplemantry motor area

medial regions

• medial prefrontal cortex

• medial orbitofrontal cortex

• ventral striatum

• left posterior hippocampus

Homo sapiens —> medial areas

Homo oeconomicus —> lateral areas

lateral prefrontal cortex

risk-seeking

• ventral striatum (nucleus accumbens)

• ventromedial prefrontal cortex

—> represent reward value of stimulus

risk-avoiding

• amygdala

• anterior insula

subjects select one of two options —> revealing their subjective values

experimentally: offering money

1. orbitofrontal cortex (OC) receives input from all sensory modalities

2. amygdala receives sensory input and projects to OC

3. OC projects widely throughout the brain

• values into goals (internal or external)

• goals into plans

• plans into behavior and action

internal or external

• Goal: get nutrients

  • internal value: get a sugary, fatty meal

  • external value: those are bad calories

• Brain activity:

  • internal: ventromedial prefrontal cortex

  • external: hippocampus, dorsolateral prefrontal cortex

goals need to be translated into plans / strategies to come up with necessary steps to be taken

Brain region: dorsomedial prefrontal areas

information from sensory associated areas —> lateral prefrontal areas

activate supplementary motor cortex —> movements

moral problem:

• do nothing and 5 people are killed

• flip switch and 1 person is killed (but you have done the action that led to death)

—> how humans switch their strategy in deciding to make difficult moral decisions

decision based on emotional cues —> stronger in medial wall areas, amygdala, striatum

decision based on external cues —> lateral areas of cortex

• Dorsomedial prefrontal cortex

  —> frame options of losses or gains

• Frontopolar cortex

  —> determine how well options map onto our long-term goals, specified by ourselves (medial) or external circumstances (lateral)

• Medial orbitofrontal cortex

  —> assign values to option based on internal needs (hunger, thirst, …)

• Lateral orbitofrontal cortex

  —> assign values to options based on external context

A “quick and dirty” and (therefore partly wrong) rule:

- - lateral areas are active in rational, external-rule-

based decisions

- medial areas are active in quick, internal-state-

driven, emotional decisions

1:1 —> unbiased

primary motor cortex

Orbitofrontal cortex