Transcript Mental Chronometry

Mental Chronometry
• Measuring the duration of mental events
with reaction time studies
© 2001 Dr. Laura Snodgrass, Ph.D.
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Donder’s Subtraction Method
• Simple RT - detection task
stimulus
detection
response
Choice RT - discrimination task
stimulus
detection
discrimination
response
Choice RT - Simple RT = time to discriminate
© 2001 Dr. Laura Snodgrass, Ph.D.
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Cued RT
• Time required to reach
“optimal readiness”
600
500
• RT is time to identify
stimulus
400
300
RT
200
100
0
pre
© 2001 Dr. Laura Snodgrass, Ph.D.
cue
500ms 1500ms
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Probe RT
• Secondary task technique
– measure mental effort of primary task by RT to
secondary task
– the more mental effort the first task takes the slower
the RT to the secondary
• Examples
– picture matching and tone probe
– task difficulty and tone (or light) probe
© 2001 Dr. Laura Snodgrass, Ph.D.
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Semantic Priming
• Speed up response to a stimulus by priming with
a related stimulus
• Shows cognitive associations
– nurse and doctor
– racial and gender biases (stereotypes)
© 2001 Dr. Laura Snodgrass, Ph.D.
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Methodological Issues
• Irreducible minimum RT
– with practice RT declines
– 90-100msec in auditory sys is fastest
• Foreperiod - interval between trials
– 1-2 sec best for optimal response
– variable foreperiod will increase RT
• Anticipation errors
– less than 100msec
• Speed-accuracy trade-off
– always measure error rate
© 2001 Dr. Laura Snodgrass, Ph.D.
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Methodological Issues
• Outliers - very long RTs
• 3 strategies
– discard
– replace
– use median not mean
• Choices
– discard any RT > 3sd larger than indiv mean
– absolute - any RT > 3,000 msec (3 sec)
– Winsorize - replace with next highest
– replace with mean for indiv or group
© 2001 Dr. Laura Snodgrass, Ph.D.
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