Drive

Reinforcement

Incentive

Basic concepts

Incentive value: Hedonic dimension

• Appetitive: any stimulus the organism is willing to work to

obtain it.

• Aversive: any stimulus the organism is willing to work to

eliminate from its surrounding.

• Obvious examples: –Food for a hungry animal.

–Pain for a healthy animal.

• What happens when the stimulus has no obvious hedonic

value?

• Betta fish are territorial and aggressively defend their area

from intruders.

• Do Betta males treat an intruder as an appetitive or

aversive stimulus?

• Pair a stimulus with their own reflection on a mirror.

• Would they work to produce a reflection or to eliminate it?

Thompson, Amer Zool, 1966, 6, 629-641.

• Bettas learn to

swim through a

hole to activate

a model of

another Betta.

Incentive value: Progressive ratio

• How can the value of an incentive be assessed?

• Progressive ratio schedules: an increasing number of responses is required to obtain the reward.

• Example: 1 – 4 – 9 – 13 – 17 – 21 – 25 …

• Breakpoint: the ratio in which no responses occur over x minutes (e.g., 5 min without responding).

• The amount of work is a function of the incentive value of the reward.

Rats (pellets) Pigeons (pellets) Rats (alcohol)

Incentive motivation: wanting vs. liking

• The evolutionary function of motivation: To fulfill physiological needs.

• But motivation is also fueled by pleasure.

• Two separate but interconnected subcortical processes direct motivation:

• Wanting: incentive salience (desire for a reward).

• Liking: hedonic pleasure (procuring reward beyond sensory experience).

• Signals acquire incentive salience (autoshaping).

[Video]

• Signals become “motivational magnets” directing behavior (PIT).

Pavlovian Instrumental Transfer-of-control

Phase Phase Test

(fear conditioning) (active avoidance)

---------------------------------------------------------------------------------------------------------

CS→Shock Response→noShock CS→Response?

noResponse→Shock

---------------------------------------------------------------------------------------------------------

CS

Sh(fear)

Manipulandum

R

CSManipulandum PLUS

+OSh

(fear)Sh

(fear)Sh

(fear)

RR!

Incentive motivation: wanting vs. liking

• Liking is reflected in behavior (taste reactivity test).

• Wanting depends on the dopaminergic mesolimbic system.

• Liking depends on opioid stimulation in “hot spots” within this system.

Incentive motivation: wanting vs. liking [Video]

NAc shell

Caudal VP

Hedonic “hot spots”: opioid stimulation increases liking.

Dopaminergic stimulation increases wanting.

Robinson et al., Current Topics in Behavioral Neuroscience, 2015, 27 (DOI 10.1007/7854_2015_387).

Incentive motivation: wanting vs. liking

Addiction

• Characterized by a progressive dissociation of wanting and liking.

• Repeated consumption leads to incentive salience (wanting).

• Repeated experience reduces pleasure (liking).

• Tolerance leads to increased doses, which sensitizes the reward system.

• Withdrawal symptoms can lead to relapse.

Berridge et al., Current Opinion in Pharmacology, 2009, 9, 65-73.

Incentive motivation: wanting vs. liking

http://www.ted.com/index.php/talks/barry_schwartz_on_the_paradox_of_choice.htmlDuration: 19.17 min

Incentive motivation: choice [Video]

•Official dogma of Western industrial societies:

•More choice → More freedom → Increase welfare

•An explosion of choice: in food, electronics, cell phones, health care, marriage options, work, lifestyles…

•This is both good and bad. What’s bad about it?

•Consequences of too many choices:

•Regret and anticipated regret (paralysis)

•Opportunity cost

•Escalation of expectations

•Self-blame

•The secret to happiness is low expectations

Paradox of choice: summary

Choice and incentive value

• Do animals have the ability to choose?

• Not only do animals exhibit free choice, but this is also a sensitive measure of incentive value.

• Forced choice:–To respond vs. not to respond.

• Free choice:–To respond to one option, or

–To respond to another option, or

–Not to respond to any option (do something else).

• In some cases, forced and free choice produce similar results.

Papini et al., Learning & Motivation, 2001, 32, 434-456.

• Rats prefer pellets to 2% sucrose.

• But 30% sucrose to pellets

• After free delivery of 2% sucrose,

rats autoshape for pellets at a

higher level than after free

delivery of 30% sucrose.

• Thus, they value 30% sucrose

more than pellets, but

• 2% sucrose less than pellets.

Choice and incentive value

• In other cases, forced choice is less sensitive than free choice.

• Rats do not differentiate between a lever paired with 12 pellets vs. a lever paired with 2 pellets when they

experience one lever at a time (forced choice).

• However, they show preference for the 12-pellet lever when they have a free choice.

• Why is free choice a more sensitive measure for detecting incentive value?

• It allows a direct, simultaneous comparison of incentive expectations.

Conrad & Papini, Journal of Experimental Psychology: Animal Learning & Cognition, 2018, 44, 422-440.

Choice and incentive value

• Free choice also sometimes yields unexpected results.

• When rats experience an incentive downshift, they actually respond in opposite directions in both types of

choice situations, even within the same session.

• Forced choice: they respond slightly more to the downshifted lever (12-to-2 pellets) than to the unshifted

lever (2-to-2 pellets).

• Free choice: they switch to the unshifted lever, at least for a few trials.

Conrad & Papini, Journal of Experimental Psychology: Animal Learning & Cognition, 2018, 44, 422-440.