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Experiment Author: Susan Campbell. Adapted from STEP and used with permission of Brian MacWhinney
Participants were shown two letters, then a cue. They were asked to identify what the cued letter was.
Comparing different conditions produced different rankings of which set of letters was easiest to identify depending on which measure (reaction time or accuracy) was used. In the data-limited condition, where the amount of time the participant saw the stimulus was limited (unfortunately, not completely replicable due to monitor refresh rate limitations), accuracy was measured. In the resource-limited condition, where the participants were instructed to respond as quickly as possible, reaction time was measured.
Reaction time and accuracy are often assumed to measure the same things, with reaction time being a finer-grained measure than accuracy. This study argues that they measure different processes and often produce slightly different results.
This experiment is counterbalanced by Subject. There are 2 possible sets of instructions that a participant could see. One set tells the participant to respond as fast as possible and the other set tells participants to respond as accurately as possible. The correct response is also counterbalanced.
In both sets of trials, participants see a fixation point. Then two letters appear, one on each side of the fixation. The letters are then replaced by an X. The X's disappear and a cue appears slightly below the position of the letters. Participants respond, pressing either the "Spacebar" or "Y" depending on the cued letter. There are 48 trials in this experiment.
NOTE: There are two versions of this experiment. RTvsAccuracynoMask is almost identical to RTvsAccuracy except that after the target letters appear, no X appears as a mask.
Santee, J.L., & Egeth, H.E. (1982). Do reaction time and accuracy measure the same aspects of letter recognition? Journal of Experimental Psychology: Human Perception and Performance, 8, 489-501.
Cited Experiment Abstract
Two experiments indicate that reaction time and accuracy are not always equivalent measures of the underlying processes involved in the recognition of visually presented letters. In conjunction with the results of previous work, our research suggests that following generalizations: (a) Under data-limited viewing conditions (the short exposure durations of the typical tachistoscopic task), response accuracy is sensitive to early perceptual interference between target and noise items, whereas reaction time is more sensitive to later processes involved in response interference. (b) Under resource-limited viewing conditions (the long exposure durations of the typical reaction time task), both accuracy and reaction time appear to be sensitive to processes occurring in the later rather than the earlier stages of processing. Since the two dependent measures do not always reflect the same perceptual processes, we suggest that the convergence of reaction time and accuracy within the context of a specific information processing model should be demonstrated empirically rather than assumed a priori.
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