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.