Expt 1: Letter Detection
Task: 2-forced choice of spatial localization. Indicate if target string is above/below fixation cross.
Independent variables: a); distractor-type ( absent/upright/inverted); b) task-difficulty (easy/difficult); c)
serial-order (first/last 3 blocks); d) spat. congruency (cong/ncong)
Dependent variables: a) accuracy score; b) reaction time
Participants: 30 undergraduate participants.
Results:
a) 2 x 2 x 3 repeated measures ANOVA (both AC and RT analysis):
main effects: task-difficulty (easy>diff) & serial-order (last>first)
interactions: task-difficulty x serial-order – n.s. of task-diff in late trials.
b) create between-group variable: distracted vs. non-distracted (15 vs. 15).
no sig. diff. between upright/inverted faces even among distracted participants.
c) replace serial-order with congruency:
main effects: congruency (c>nc) & task-difficulty (easy>diff).
no interactions.
Conclusion:
a) distractor-type does not influence distractability effectiveness
(even among easily distracted individuals).
b) assumptions of task-difficulty is correct.
c) practice improve easy (NOT diff) task perform.
d) cong. effect shows that spatial orienting is at work.
e) design flaw: task strategy. could be solved by inference.
Accuracy scores on letter-detection task
1
0.95
0.9
0.85
easy-first
diff-first
0.8
easy-last
diff-last
0.75
0.7
0.65
0.6
absent
inverted face upright face
Expt 2: Letter Detection
Task: 2-forced choice of detection (absent/present).
Improvements: a) no inference possible; b) only difficult letters used, no practice effect; c) preserve task
difficulty variable; d) reduce image size by increasing distance to display.
Independent variables: a); distractor-type ( absent/upright/inverted); b) task-difficulty (present/absent);
Dependent variables: a) accuracy score; b) reaction time
Participants: 35 undergraduate participants
Results:
a) 2 x 3 repeated measures ANOVA
main effects: task-difficulty (present>absent) (F(1,34)=57.4, p<0.001); faces (F(2,68)=2.15,
p=0.125), no interactions
b) pair-wise comparisons reveal p=0.47 between absent and upright face.
c) same for RT analysis: no significance for faces even with pair-wise comparison.
Discussion:
a) Upright faces do not bias spatial visual attention – impair visual search in central location.
b) Visual search is working. lack of FDE due to no visual mask that attenuates unfamiliar face
stimuli?
Expt 3a: Letter Detection (Backward visual mask)
Task: as Expt2 but with backward visual mask
Participants: 8 undergraduates
Improvements: Introduction of visual mask to replicate conditions of original FDE expts. Might be
attenuation of unfamiliar face stimuli that results in FDE.
Results: 2 x 3 ANOVA. Significant main effect for Task difficulty. No main effect for faces
Expt 3b: Letter Detection (dist. between target and distractors halved)
Task: as Expt 3a but distractors are half distance to target display.
Participants: 8 undergraduates
Results: Main effect of task-difficulty; NOT face-type.
Expt 4: Dot probe task
Task: 2-forced choice of target detection. Indicate position of target that follows on to one of two prime
images positioned either side of a fixation cross.
Improvement: Remove salient endogenous orienting cue that may be over-riding automatic exogenous
orienting cue of face-salience.
Independent variables: a) prime type (upright face/inverted face); b) timings (60/60+540/600) ; c) pairings
(same/not-same)
Dependent variables: a) reaction time
Hypothesis: If faces are effective orienting cue, significant 3-way interaction.
a) 60ms: face-notsame > nonface-same = face-same > nonface-notsame
b) 60+540ms: IOR – reverse pattern
c) 600ms: IOR or orienting.
Participants: 18 undergraduate participants.
440
Results:
a)
430
Reaction time
Main effect of timings. Fastest RTs for
600ms > [60ms = (60+540)ms].
b) No significant interactions. Although Face x
Same (F(1,17)=3.324, p=0.09)
420
410
upright
400
inverted
390
380
370
Conclusion:
360
a) effect of habituation with 600ms presentation
not-same
b) no main effect of face or predicted interaction
to indicate that upright faces are salient
orienting cues.
c) interaction of face x same is encouraging, but hardly significant.
Follow-up?
a) use of moving faces in dot-probe?
b) use of scrambled instd of inverted faces? use of less-familiar object that
is not vertically-bounded e.g. butterfly.
same