Classical Conditioning I
Classical Conditioning
Classical or Pavlovian conditioning
Conditioned Stimulus (CS)
Unconditioned Stimulus (US)
Automatically elicits a response (reflex)Unconditioned Response (UR)
Food, Water, Sex, Pain, etc.
Initially “neutral” – Does not initially trigger same response as does the US
lights, sounds, tastes, odors, etc.
After pairings with the US, elicits a conditioned response
Some response systems that participate in classical conditioning
• Endorphins and analgesia
• Sexual arousal
• Immune suppression/enhancement
• Fear
AutoshapingWhen there is a contingency between a tangible CS
and a pleasurable US, the CR is directed at the CS. Sign tracking (cf. Goal tracking)
Pigeonsresponse: peck key light CS
Rats
key light CS food US
response: handle ball bearingball bearing CS food US
insert lever CS food USresponse: lick lever
Autoshaping Movies
Long-box autshaping
Omission training
Fear Conditioning
(shock)
(tone)
Notation:
Tone +
Or
ToneShock
After one or two pairings…
(CS)
Blood pressure
Heart Rate
Stress Hormones
Freezing
(CR’s)
Conditioned Suppression
Suppression Ratio
a = responses during the CS
b = responses prior to the CS
aa + b
After 10 Tone-Shock trials: a = 3; b = 20. 3/(3+20) = 0.13
On first Tone-Shock trial: a = 30; b = 30. 30/(30+30) = 0.50
Fear-Potentiated Startle (Davis)
Tone ShockTrain:
Test: Startle Stimulus (Loud Noise) Alone
Vs.
Startle Stimulus + Tone
DV: How high do they jump?
Startle Amplitude
0
20
40
60
80
100
120
Tone No Tone
Sta
rtle
Am
plit
ud
e
Feedback
vs. Feed-forward
Some properties of classical conditioning
Discrimination
0
0.2
0.4
0.6
0.8
1
1.2
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
Trials
Re
sp
on
se
Str
en
gth
CS+
CS-
Generalization
CR’s
Tone frequency
Trained frequency
What determines the form of the CR?
Stimulus Substitution
Behavior Systems
Opponent Processes
Stimulus Substitution (the CS takes the place of the US)
• Pavlov: UR = Salivation, CR = Salivation
• Cocaine: UR = Activity, CR = Activity
• Cyclophosamide: UR & CR = immune suppression.
• Autoshaping: CR for water = Closed beak, CR for grain = Open beak
Form of the CR in Sign Tracking
From Jenkins & Moore, 1973
UCS = Water (note the closed beak)
UCS = Food (note the open beak)
video
However…
• Fear conditioning: CR = freezing, UR = activity
• CS can determine form of CR
Form of CR depends on CS
However…
• Fear conditioning: CR = freezing, UR = activity
• CS can determine form of CR
• Interval between CS and US matters– Long delay: General search CR– Short delay: Focal search CR
Behavior Systems Theory
• Holland (1984); Timberlake & Silva; Akins
The CS and US engage the same “behavior system” – e.g., appetitive, sexual, defensive.
The form of the CR depends on the length of the delay between CS and US.
Overt CR is flexible – depends on situation
Another View: Opponent Process Theory
Conditioning helps maintain homeostasis
US’s divert organism away from homeostasis
time
Body temp
Enter sauna
Begin cooling response
=Vasodilation
sweating
98.6
Opponent Process Theory of Motivation
Siegel
heroin
Ave. C
Buddy Jimmy
Favorite belt
Etc. Euphoria
Big departure from homeostasis
Siegel
heroin
Ave. C
Buddy Jimmy
Favorite belt
Etc. Euphoria
Smaller departure from homeostasis
Siegel
heroin
Ave. C
Buddy Jimmy
Favorite belt
Etc. Euphoria
Even smaller departure from homeostasis
Siegel
heroin
Ave. C
Buddy Jimmy
Favorite belt
Etc. Euphoria
Departure from homeostasis
Siegel
heroin
New Context
Euphoria
Departure from homeostasis
Siegel
Time since admin.
Conc. Of drug in Brain
CS US
Montaigne:
“My appetite comes to me while eating”
-Of Vanity (1500-ish)
