PRIMING OF MENTAL OPERATIONS 169
SOAs. Prime and masking stimuli were constructed toobtain Type B
metacontrast masking functions (Breit-meyer, 1984), partly
consisting of decreasing primerecognitionperformance with
increasing SOA. It was ex-pected that priming and prime recognition
would followdifferent time courses, constituting a double
dissociationof priming and prime recognition.
MethodParticipants. Six students from the University of
Braunschweig
(5 women, 1 man), from 20 to 28 years of age (M 5 23.0
years),participated in the experiment. All reported that they were
right-handed, and all had normal or corrected-to-normal vision.
Eachparticipant took part in three 1-h sessions, receiving course
creditfor participation.Stimuli. Stimuli similar to those
introduced by Neumann and
Klotz (1994) were used. Square and diamond shaped stimuli
servedas prime and mask stimuli (see Figure 1). They were
presentedblack on white on a computer monitor, at a refresh rate of
60 Hz.The stimuli were positioned at the fixation cross in the
center of the
monitor. Squares and diamonds consisted of the same number
ofpixels. Prime squares and diamonds subtended visual angles
ofabout 1.0 and 1.5 in height and width. The height and width of
theouter contour of the masks subtended about 1.6 and 2.2 of
visualangle for square and diamond-shaped masks, respectively.
Theprimes were 1 pixel smaller than the inner outline of the
masks.Prime duration was 34 msec; mask duration was 51 msec.
Primemask SOA varied randomly from trial to trial, in steps of 17
msec,from 34 to 119 msec. The primes were congruent with the masks
inhalf of the trials, with congruency varying randomly between
trials.Visual and auditory stimuli were presented 102 msec after
maskoffset for 102 msec; these were irrelevant for the task in
Experi-ment 1 but were relevant in Experiment 3 (see below). Thus,
thesestimuli served as distractors in Experiment 1 (see Figure 2).
An au-ditory stimulus of 1000 Hz and 100-msec duration served as
errorfeedback.Tasks. (1) In the choice RT task, the participants
responded to
diamond-shaped (square) mask stimuli by pressing the left
(right)ALT key on the keyboard with the left (right) index finger.
(2) In thelast session, the participants were informed about the
presence ofprimes and were to respond to the shape of the primes
without pres-
Fixation
700 msec
Prime
34 msec
SOA
34 119 msec
Target /Cue
51 msec
Fixation
102 msec
Distractor/ Target
102 msec
time
Figure 2. Schematic diagram of stimulus events in Experiments
14. In thechoice reaction time (RT) task, the participantsused the
mask as a target in Ex-periment 1, but as a cue in Experiments 24.
The stimulus presented after themask was irrelevant in Experiment 1
but was used as the target in later exper-iments. Priming effects
were assessed by the effects of primemask congruencyon RT. In the
prime recognition task, the participants reported the prime.
Timecourses of priming and prime recognition were assessed by
varying stimulusonset asynchrony (SOA) between prime and mask
randomly from trial to trial.Note that the bars in the last frame
were either green or red. Experiment 3 usedthe color bars and tones
as targets in the choice RT task. Experiment 4 used nocolor bars at
all but presented sounds via headphones as targets in the choiceRT
task.
