Time related confounds and counterbalancing 6.1

Question 1

History Effects

Answer 1

environmental/societal changes over

time that influence behaviors

Question 2

Maturation Effects

Answer 2

biological or psychological changes over time that
are independent of external events

Short-term maturation effects
•Change of mood, get bored, tired, hungry, anxious, stop paying attention

Longer-term maturation effects
•Changes in knowledge (i.e., learning), health, etc.

Question 3

Instrumentation Effects

Answer 3

•Change in the DV due to changes in the measuring device

Question 4

Carryover effects

Answer 4

•when an effect ”carries over” from one experimental condition to
another
Example:
•Manipulating moods back and forth

Question 5

Practice effects

Answer 5

•Ppts get better 
at tasks with 
practice
•Useful to 
include practice 
trials at the 
beginning of an 
experiment

Question 6

Fatigue effects

Answer 6

•Ppts get tired/bored 
after a while
•Don’t make the 
experiment 
unnecessarily long
•Include breaks between 
blocks of trials

Question 7

Counterbalancing

Answer 7

•Control for time related confounds by balancing the order that
conditions (and/or items) are presented

Counterbalancing
•Order of conditions
•Order of lists and/or Items

Question 8

Counter balancing types

Answer 8

• Complete within-subjects counterbalancing
• Each ppt sees every possible sequence of conditions
• ABBA counterbalancing
• Complete counterbalancing with 3+ conditions
• Incomplete within-subjects counterbalancing
• Ppt’s don’t see each possible order of conditions
• Random order with rotation
• Latin square
• Random order for each ppt

Question 9

ABBA counterbalancing

Answer 9

• Repeated measures design with two conditions, A&B
• Trials for a ppt are presented in alternating ABBA or BAAB patterns
• ABBA
• BAAB

Question 10

Counterbalancing with 3+ conditions

Answer 10

•3 condition example
•Determine every possible combination (n!); 3! = 321 = 6
•ABC, ACB, BAC, BCA, CAB, CBA
•create lists with those combinations in different random or pseudo random
orders

Question 11

Incomplete Counterbalancing

Answer 11

• Random order with rotation (incomplete counterbalancing)
• 4+ conditions
• Figure out every possible sequence
• 4 conditions = 4! = 24 sequences
• 5 conditions = 5! = 120; 6 conditions = 720 sequences!
• Create multiple lists:
• Randomly assign a subset of sequences to each list
• Rotate participants through the lists (or randomly assign the list to each ppt)

Question 12

Latin squares

Answer 12

•Incomplete counterbalancing (usually)
•Each condition appears once in each row and
column
•Separate Latin squares for each combo
•Use these orders as the basis for blocks and lists
•Each condition occurs equally often in every
sequential position
•Every condition precedes and follows every other
condition exactly once

Question 13

Random vs pseudo random techniques

Answer 13

• Random
• Present the conditions in a new, random order for each participant
• Pseudo random
• Impose some structure on the randomness

Question 14

Counterbalancing items

Answer 14

•In a repeated measures design, there are multiple observations of
each condition
•Each observation is associated with a trial
•Often, each condition consists of multiple items (specific stimuli)
•The order of individual items within a condition is often determined
randomly, either via predetermined lists or in real time

Question 15

Hawthorne effect/ observer effect

Answer 15

•The effect of being tested or 
observed influences ppt 
behavior (reactivity).
•A concern for all research 
where ppts know they are 
being observed
•Different from the 
experimenter effect

Question 16

Regression toward the mean

Answer 16

Regression toward the mean – extreme performance is typically followed by
more average performance