There are two reaction time experiments to choose from. One uses auditory stimuli and the other visual stimuli. Otherwise the experiments are exact replicates of each other. These experiments give students the opportunity to determine whether their reaction times are reliably different for reaction time tasks that require slightly different decisions. Students who choose to replicate the experiment using the second stimulus type (which would be auditory for those who begin with the visual tasks and visual for those who begin with the auditory tasks) can compare results from the two experiments to see if their reaction times for the different tasks were reliably faster for one stimulus type than the other.
Design
Each reaction time experiment uses
a one-way experimental design with three levels to the independent variable--Type
of Task. The three task types are:
(1) A simple reaction time task in
which participants press a key as quickly as possible after the stimulus
(auditory or visual) has been presented.
(2) A Go/NoGo reaction time task in
which participants respond to one particular event (e.g., a red color
or a horn sound) but ignore other events (e.g.,a blue color or a rooster
cry)
(3) A choice reaction time task in
which participants respond differentially to two stimuli by pressing one
key for event A and a separate key for event B.
The Task variable is manipulated within-subjects,
which means that each participant gets all three tasks, but to control
for potential order effects across different participants, the order in
which the tasks are presented in randomly determined for any one research participants. The dependent variable is the time from the onset of the stimulus
to the keypress reaction measured to the nearest millisecond. For choice-reaction
time responses, responses are judged for correctness also.
«
Return to Top»
After gathering information on the participant's
gender and age, the program assigns the order in which the
three tasks will be presented. The simple task consists of 20 trials.
On each, the participant presses a key as rapidly as possible following
the onset of the target event, which is the color red for the visual
experiment or a "whistle
down" sound for the auditory experiment. The Go/NoGo task consists of around 40 trials. The exact
number is indeterminate because there is a random decision on each trial
whether to present the target "Go" stimulus, which is the color red for
the visual experiment or the whistle down sound for the auditory experiment. Trials continue to be presented until 20 target events have occurred.
The only data 
recorded
are the participants' reaction times for each of the 20 target trials. The
number of trials for the Choice Reaction Time task will be 20 or more depending
on the participant's accuracy because the program requires that 20 correct
responses be made. A correct response is pressing the key assigned
to each of two events. In the visual experiment for example, the > key
is pressed when the color red appears and the < key is pressed when blue
appears. The same keys are used in the auditory experiment but the events
are a whistle down sound and a whistle up sound. Before beginning the
Choice Reaction Time tasks there is an opportunity to listen to both sounds and
participants should do so several times to
be sure they are ready for the actual Choice task.
The
total experiment can be completed in about 7-8 minutes. The first trial
for each task begins following a "Get Ready" signal that stays on the
screen for from 1 to 3 seconds. The Get Ready interval is varied randomly so
that participants cannot use temporal cues to anticipate the appearance of a
stimulus. Following the first trial, there is a feedback screen for each
trial, as illustrated in the screen shot to the right. On the screen is a
next button that participants use to initiate the next trial. It can be
activated using either the mouse of keyboard. When participants make
an incorrect response there is an additional screen informing them of their
mistake, as illustrated by the screen shot below.
.« Return to Top»
Analysis
Students should begin by computing descriptive statistics for the 20 reaction times recorded for each of the three tasks. They will observe that these differ not only in central tendency (means and medians) but in variability as well. Also, the times will be positively skewed. To determine whether reaction time was affected in a systematic way by the nature of the task, they can group the mean or median reaction times for a set of research participants and then perform a one-way analysis of variance on the grouped data.
If the research participants have conducted both the auditory and visual versions of the Reaction Time experiment, they can expand the groups analysis to a two-way analysis in which they determine whether stimulus type affected reaction times in a systematic way and whether stimulus type interacted with task.
In
data sets where there is variability in the ages of the participants, age can be
analyzed for its effect. A correlational analysis would reveal whether
there was a positive association between age and reaction time and whether it
was equally strong for each type of task.
« Return to Top»
Last revised:November 01, 2003 07:01:31 PM
Copyright© 1995 The University
of Mississippi. All rights reserved.
Questions about this page?PsychExps