Comparing Thompson’s Thatcher effect with faces and non-face objects
Elyssa
1
Twedt ,
David
2
Sheinberg
& Isabel
1
Gauthier
Vanderbilt University1, Brown University2
Poster Number #
Introduction
Stimuli Examples
Results
Animal
Thompson’s Thatcher Illusion
Question: What influences the Thatcher effect?
We quantified the Thatcher effect using sensitivity, comparing performance on
upright and inverted trials (d’ upright - d’ inverted).
Locally inverted the eyes and mouth of a face to create a
“Thatcherized” face
Hypothesis 1: Perceived bizarreness influences size of Thatcher effect
Method:
•Subjects rated images on bizarreness - Scale of 1 (normal) to 7 (very
bizarre)
•Correlated ratings
with size of Thatcher effect
Global inversion makes local
changes difficult to detect
Car
x
x
x
Upright Thatcherized face looks
grotesque
N=21
Close-up Scene
X = N.S.
Overall:
•Significant Thatcher effect for all categories relative to zero
•Largest Thatcher effect for HF and LF words
Empirical research limited to faces - many assume the effect is face
specific
•Thatcher effect is not face specific or largest for adult faces
Face Categories:
Demonstration of TE in words (Parks, 1983):
•If familiarity was a determining factor for the Thatcher effect, adult faces should show
a larger Thatcher effect than animal faces, which was NOT the case.
HF Non-word
•If perception of bizarreness were an important factor of the Thatcher effect, we would
predict grimacing faces, already bizarre without Thatcherization, to show a smaller
Thatcher effect - but adult and grimacing faces show similar Thatcher effects.
Objects/Scenes:
•Smaller Thatcher effects than faces or letter-strings. Why? Upright and inverted d’
values suggest this is due to smaller inversion effect, rather than greater difficulty
detecting changes.
Questions
Same-Different Task
•Is the Thatcher effect face specific?
Image pairs (always from the same identity and in the same orientation)
presented sequentially both upright and inverted
Letter-Strings:
•Is the Thatcher effect stronger for adult faces?
Trial Types:
•Same: Normal, Thatcherized 1, Thatcherized 2
•Different: Normal vs. Thatcherized 1, Normal vs. Thatcherized 2
•Main effect for word type and word frequency - Words showed larger Thatcher
effects than non-words and LF letter-strings showed larger Thatcher effects than HF.
Interestingly, although inverted words show no advantage over inverted non-words,
we find a word frequency advantage for both types of inverted strings.
Letter-Strings
3.5
2.5
2
1.5
1
0.5
Response
We created non-words by transposing letters from actual words
750 ms
300 ms
750 ms
2250 ms
ct
Ef
fe
at
ch
er
rt
ed
Th
U
In
ve
LF
LF
H
F
Th
at
ch
er
F
In
ve
r
te
d
gh
t
H
F
Up
ri
We created 2 levels of Thatcherized images by locally inverting 1 and
2 internal features (e.g., eyes and mouth) 180°
pr
ig
ht
0
+
Method:
•Defined orientation familiarity: Speed at which an observer can determine
an object’s orientation
•Recorded RT and correlated with size of Thatcher effect
Results:
•Insignificant correlation (r = -0.113)
•Perhaps we need a better measure of object familiarity
Conclusions
Our results suggest the TE is not exclusive to faces - it does not appear to
uniquely depend on factors such as expertise or the bizarre appearance of
the transformation.
Faces and letter-strings showed larger TEs than objects/scenes, although all
categories showed significant Thatcher effects.
•Subgroup differences may be explained by experience with faces and
letters, which transfers broadly to similar objects.
References
LF
We chose categories that would help test the role of familiarity and
bizarre expression in experiencing the Thatcher effect
3
ct
d' (or delta d' for TE)
We collected images from 12 categories:
•Faces: Adult, grimacing, baby, animal
•Objects/Scenes: Buildings, cars, close-up scenes, large scenes
•Letter-strings: HF/LF words, HF/LF non-words
Ef
fe
Sample trial:
Hypothesis 2: Familiarity with an object at a given orientation
Non-Words
Words
H
Method
Correlation suggests that as an image appears more bizarre, the size of the
Thatcher effect increases. However, correlations for face categories and
objects/scenes are opposite - suggests that bizarreness is NOT a major
predictor of the Thatcher effect
Bartlett, J. C., & Searcy, J. (1993). Inversion and configuration of faces.
Cognitive Psychology, 25, 281-316.
Boutsen, L., & Humphreys, G. W. (2003). The effect of inversion on the
encoding of normal and “Thatcherized” faces. Quarterly Journal of
Experimental Psychology Section A – Human Experimental
Psychology, 56, 955-975.
Parks, T. E. (1983). Letter to the Editor. Perception, 12, 88.
Thompson, P. (1980). Margaret Thatcher: A new illusion. Perception, 9, 483484.
Valentine, T., & Bruce, V. (1985). What’s up? The Margaret Thatcher illusion
revisited. Perception, 14, 515-516.