© 2001 Dr. Laura Snodgrass, Ph.D.1 Mental Chronometry Measuring the duration of mental events with reaction time studies

© 2001 Dr. Laura Snodgrass, Ph.D.2 Donder’s Subtraction Method Simple RT - detection task Choice RT - discrimination task discrimination Choice RT - Simple RT = time to discriminate detectionstimulusresponse detectionstimulusresponse

© 2001 Dr. Laura Snodgrass, Ph.D.3 Cued RT Time required to reach “optimal readiness” RT is time to identify stimulus

© 2001 Dr. Laura Snodgrass, Ph.D.4 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.5 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.6 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.7 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