Supplementary Figure legends
Figure S1. Position-defined priming in Experiment 1 with all nine participants. (a)
Schematic of the trial sequence. The prime stimulus was always defined by position cues.
The probe stimulus could either also be defined by position cues (within-cue) or by
orientation cues (cross-cue). Shown here are primed trials, in which the probe and prime
are the same shape. In unprimed trials, the probe would be the opposite shape as the
prime. (b) The magnitude of the priming effect (how much faster response times were for
primed relative to unprimed trials) is plotted for the four priming conditions: visible and
invisible primes, within-cue and cross-cue condition. As in the main analysis, there was a
significant interaction between awareness and integration (F(1,8)=6.88, p=0.03), but no
main effects (awareness: F(1,8)=2.81, p=0.132; integration: F(1,8)=1.04, p=0.339). (c)
Median response time is plotted for every trial type. In both b and c, data reflect mean
across participants, error bars denote ±1 standard error of the mean (between-subject
variance removed).
Figure S2. Orientation-defined primes in Experiment 2 with all nine participants. (a)
Schematic of the trial sequence. The prime stimulus was always defined by orientation
cues. The probe stimulus could either also be defined by orientation cues (within-cue) or
by position cues (cross-cue). Shown here are primed trials, in which the probe and prime
are the same shape. In unprimed trials, the probe would be the opposite shape as the
prime. (b) The magnitude of the priming effect (how much faster response times were for
primed relative to unprimed trials) is plotted for the four priming conditions: visible and
invisible primes, within-cue and cross-cue condition. As in the main analysis, there was a
significant interaction between awareness and integration (F(1,8)=30.66, p=0.001), but no
main effects (awareness: F(1,8)=0.06, p=0.807; integration: F(1,8)=0.11, p=0.754). (c)
Median response time is plotted for every trial type. In both b and c, data reflect mean
across participants, error bars denote ±1 standard error of the mean (between-subject
variance removed).
Supplementary Information
Analysis of response times separately for each condition
Experiment 1
A three-way repeated-measures ANOVA with factors awareness (visible, invisible),
integration (within-cue, cross-cue) and priming (primed, unprimed) revealed a significant
effect of priming (F(1,6)=8.84, p=0.025). Moreover, there was a significant three-way
interaction which is the statistical equivalent of the interaction we reported above for the
priming effect (F(1,6)=15.06, p=0.008). The lack of cross-cue priming for invisible primes
was probably due to shorter response times when the prime was visible compared to
when it was invisible, although this difference did not reach significance (paired t-test:
t(6)=-2.39, p=0.054). For unprimed trials, however, response times were the same for
visible and invisible primes (t(6)=0.04, p=0.97). This suggests that conscious processing of
the position-defined prime afforded participants with a benefit speeding up their
behavioural responses.
Experiment 2
A three-way repeated-measures ANOVA with factors awareness (visible, invisible),
integration (within-cue, cross-cue) and priming (primed, unprimed) revealed a significant
effect of priming (F(1,6)=11.71, p=0.014). Moreover, overall response times visible trials
were faster than those to invisible trials (F(1,6)=7.8, p=0.031). There also was a significant
interaction between awareness and integration (F(1,6)=17.38, p=0.006), and a significant
three-way interaction which is the statistical equivalent of the interaction we reported
above for the priming effect (F(1,6)=28.67, p=0.002). The response times for primed trials
in the within-cue condition were significantly shorter for visible than invisible primes (paired
t-test: t(6)=-4.65, p=0.003). In contrast, for unprimed trials response times were similar
regardless of whether the prime was visible or not (t(6)=-1.8, p=0.122). This suggests that
conscious processing of orientation-defined primes is necessary to speed up participants’
responses when the probe is also defined by orientation.
Experiment 3
Analysing the response times for all experimental conditions separately (Figure 4c)
revealed that responses to within-cue primed trials were faster than that to unprimed trials
when the prime was visible. In all other conditions, the response times did not change
between visible and invisible trials. This was supported by a three-way repeated-measures
ANOVA with factors awareness (visible, invisible), integration (within-cue, cross-cue) and
priming (primed, unprimed), which showed a significant difference between within- and
cross-cue conditions (F(1,5)=9.98, p=0.025) and a main effect of priming (F(1,5)=7.9,
p=0.038), but no difference between visible and invisible trials (F(1,5)=1.84, p=0.233). The
response time to primed within-cue trials was significantly shorter than for invisible primed
trials (t(5)=-2.99, p=0.031), but there was no difference for unprimed trials (t(5)=0.29,
p=0.787).
Experiment 4
We also analysed the response times in all of the conditions separately (Figure 5c). A twoway repeated-measures ANOVA with factors awareness (visible, invisible) and priming
(primed, unprimed) showed that there was a significant priming effect (F(1,12)=8.06,
p=0.015). Moreover, overall response times for visible trials were significantly shorter than
for invisible trials (F(1,12)=16.6, p=0.002).
Confirming effectiveness of masking
Experiment 1
In order to confirm that our method of rendering the primes invisible was effective,
participants performed a brief test session after the main experiment. Here, the trial
sequence was truncated after the presentation of the first stimulus and participants judged
whether it was a square or diamond. This showed that while performance at this task was
unsurprisingly very high when the stimulus was visible (mean accuracy: 0.96±0.01), when
the stimulus was invisible, participants were unable to judge the shape: performance was
low (0.52±0.02) and not significantly different from chance (t(8)=0.99, p=0.18). Consistent
with this, no participant reported being aware of the fact that any stimulus had been
presented during invisible intervals when debriefed after the experiment.
Experiment 2
As in the first experiment, after the main experiment participants performed a quick test
session to test that rendering the primes invisible had been successful. Again,
performances for visible stimuli was very high when the stimulus was visible (mean
accuracy: 0.95±0.02), but when the stimulus was invisible, performance was low
(0.47±0.02) and not significantly different from chance (t(9)=-1.81, p=0.104). As with the
Gaussian elements in the previous experiment, after the experiment none of the
participants reported being aware that invisible Gabor patches had been presented in
invisible trials.
Supplementary Materials and Methods
Participants
Nine healthy participants (3 male, 1 left-handed, age: 22-41) with normal or corrected-tonormal visual acuity, gave written informed consent to participate in Experiments 1 and 2.
Six participants (2 male, all right-handed, age: 22-32) participated in Experiment 3.
Thirteen healthy participants (9 female, 2 left-handed, age: 22-41) participated in
Experiment 4. All except for one (author DSS), were naïve to the purpose of the study. The
procedures were approved by the local ethics committee.
Stimulus parameters
Orientation cues were Gabor patches (standard deviation and carrier wavelength: 0.42°,
i.e. carrier frequency: 2.38 cycles/°) that either had cardinal or oblique orientations to
create a square or diamond shape, respectively. Position cues had luminance profile
described by a difference of two Gaussians (standard deviation: 0.42° and 0.21°,
respectively). Cues were presented on a uniform grey background at low but suprathreshold contrast (0.07). Stimuli subtended 17.45° of visual angle and were presented at
the centre of a CRT screen (resolution: 1024*768, refresh rate: 120Hz). Participants
viewed the screen at a distance of 67cm and were stabilised by a chin rest with forehead
support.
In Experiment 4, stimuli also comprised 8 elements, all of which were Gabor patches, i.e.
orientation cues. Elements were placed randomly with the constraint that the distance
between any two elements must be at least 2.7° of visual angle. The position of elements
was randomized on each trial. The parameters of Gabor patches was identical to the other
experiments. In half of the stimuli, the orientation of all elements was cardinal (half
orientated at 0°, half at 90°). In the remaining half of stimuli, the orientations were all
oblique (half at 45°, half at 135°). This ensured that the content of local information was
comparable to the orientation-defined shape stimuli of the other experiments, while there
was no global shape interpretation.
Procedure
Participants completed 800 trials in Experiments 1-3, which were subdivided into 25 blocks
with participant-terminated resting breaks. There were 16 trial conditions each of which
appeared twice within each block in a pseudo-randomized order: 2 probe shapes (square,
diamond) X 2 cues (orientation, position) X 2 priming states (primed, unprimed) X 2
awareness conditions (visible, invisible). Altogether, there were thus 100 trials for all the
combinations of interest. Since in Experiment 4 there was no cross-cue priming condition,
trial numbers were half than that in the other experiments.
Confirming effectiveness of masking
After each main experiment, participants further completed a brief test session to ensure
that rendering the primes invisible had been successful. Here, the trial sequence was
similar to the main experiment, except that it was truncated after the presentation of the
prime and participants were asked to distinguish whether the shape they saw was a
square or a diamond. The fixation dot during the stimulus presentation was blue. In half
the trials the stimulus was again rendered invisible. There were thus four stimulus
conditions (2 shapes X 2 awareness conditions) each of which was presented 8 times per
block, with four blocks in total. This resulted in 64 trials each for the visible and invisible
condition.