Experimental PsychologyPSY 433

Chapter 9

Conditioning and Learning (Cont.)

Dressage Example

http://www.youtube.com/watch?v=zKQgTiqhPbw

The horse responds to hand and leg cues that vary by location to signal different moves.

Horses begin to be trained at age 2 and it takes around 13-15 years to be this good (this horse is 9 years old and is unusual).

Riders must be trained too, to give the right cues and not confuse a trained horse.

Behavior is shaped.

Choosing an Experimental Design

Between vs within subjects designs offer different tradeoffs, but there are more than practical considerations at stake. Choice of design may affect the actual

outcome of the research. Sometimes using a between-subjects and a

within-subjects design produces different results. Carryover effects may exist without the

experimenter’s knowledge.

Order Effects

Order effects (practice effects) = experiencing one level affects behavior in another level Effects of practice, boredom, fatigue

Example: Does content (biology text vs. novel) affect proofreading speed? Order is Biology-Novel

Order effects are controlled in within-subjects designs by randomizing or counterbalancing the presentation orders.

Order Effects in Proofreading

Group 1Biology

1

(no practice) (practice)Novel

2

Group 2Biology

1

(no practice) (practice)Novel

2

Differential Carryover Effects

Carryover effects, differential/asymmetrical transfer effects occur when experiencing one level affects performance on the next.

The effect of the first level on the second level differs depending on which comes first. Effect of B following A ≠ effect of A following

B Confound occurs when one level

consistently precedes the other.

Differential Carryover Effects in Problem Solving

Group 1 Neutralinstructions

1

(no practice) (practice)

2

Group 2

1

(no practice) (practice)

2

Specialinstructions

Neutralinstructions

Specialinstructions

Classical Conditioning Example

Grice and Hunter (1964) - human conditioning UCS is air puff; UR is blinking Vary CS intensity (loud or soft tone) Done between-subjects or within-subjects

500 ms CS – 500 ms ISI – US Varying CS intensity in BS design has no

effect on % CR Varying CS intensity in WS design has large

effect.

Contrast Between Stimuli

In a WS design, subjects can compare two levels of a stimulus in the same experiment and may respond to the two stimuli differently.

This effect occurs despite the randomization and counterbalancing that were used to control for differential order effects: First, choose a random order (LSSLSLLLS) Then counterbalance the random order:

½ got it, ½ got the reverse (SLLSLSSSL)

Instrumental Conditioning Example

Bower (1961) –3 groups of rats trained to run down an alley (maze) for food.

Two IVs: kind of reward & color of maze. Reward:

Constant 8 – got 8 pellets per maze run Constant 1 -- got 1 pellet per maze run Contrast – got 1 pellet in one colored maze, 8

in the other colored maze (black/white) All 3 groups: ½ got black & ½ got white maze.

ABBA Counterbalancing

Define 2 conditions: A and B or S and L In Bower’s case, 1 pellet (S) & 8 pellet (L)

Present in order: ABBA (SLLS) If order effects are linear, they will then be

distributed evenly across conditions. If nonlinear, do not use ABBA, or give

practice trials first. Bower used both ABBA and BAAB. Use Balanced Latin Square with >2 groups.