“Ghostly Gaze” Illusion
What to see
The neighbouring face image changes between focused and defocused. When in focus, the face looks to the left. When defocused, the face looks to the right!
I also notice a hysteresis: when going from focused to defocused, the point where perception switches to rightward gaze requires more defocus than on the reverse until the gaze flips to the left again.
What to do
To convince yourself that it is really just defocus, press the “focus” button and walk away from your monitor – decreasing size effectively defocuses the image in your eye. Alternatively, you can defocus by screwing up your eyes, taking off glasses or any other method that blurs your vision.
You can manually set the blur level with the buttons ›focus‹ or ›defocus‹, or double-clicking the slider, then drag it.
Dr. Jenkins writes in his paper of 2007: “The figure was constructed by combining spatial-frequency information from two whole-face images that differed only in their gaze direction. A low-pass Gaussian filter (9 cycles per image width) was applied to the right-gaze version of the image, and a high-pass Gaussian filter (13.3 cycles per image width) was applied to the left-gaze version.”
He uses a method, described in 1994 by Philippe G. Schyns & Aude Oliva, that incorporates two slightly different images in one single hybrid image: one image high-pass filtered, the other low-pass filtered. When viewed in focus, the higher spatial frequency image ‘wins’. When blurring, by whatever means, only the low-pass image remains. This technique can be applied to many image types, it is also employed by “Mr. Angry and Mr. Smile” (next page).
This demonstration was created with kind permission of Dr. Rob Jenkins, Department of Psychology, University of Glasgow, UK.
Jenkins R (2007) The lighter side of gaze perception. Perception 36:1266–1268
Schyns PG, Oliva A (1994) From blobs to boundary edges: Evidence for time and spatial scale dependent scene recognition. Psychol Sci 5:195–200