Perceptual Rivalry and Reversible Figures:

1. Monocular Rivalry:
        It is difficult to demonstrate binocular rivalry on the web, but a good idea of the perceptual switching of binocular rivalry can be gained by looking at monocular rivalry. The alternating dominance of the orthogonal, complementary-coloured gratings is  similar to binocular rivalry with orthogonal gratings and seems to share similar neural mechanisms, thus taking the emphasis away from binocularity and placing it upon the resolution of ambiguity.
2. Necker Cube:
3. Animated Necker Cube:
    The switching may become more apparent in this version, especially when the spatial properties of the intruding objects conflict with your current interpretation of the figure's perspective.
4. Bonneh's Illusion: Invented by Yoram Bonneh.
    At first sight this does not seem to be related to reversible figures. Nevertheless, the cyclic disappearance of the yellow discs has many similarities with the cyclic changes of perceptual rivalry. The duration of the disappearance-reappearance cycle is correlated with the binocular rivalry cycle in an individual and the disappearance phase can be cut short by disrupting Left hemisphere activity with TMS, just as with binocular rivalry.
This is the pattern used on the Catalyst program, from which I received hundreds of emails. Perhaps the most common comment was that the dots did not disappear at all. Note that that this does not mean a "slow switch" , for which one would have to see dots disappear and reappear again, but slowly. The most common reasons for the dots to fail to disappear include:- stress and tiredness, depression, anxiety, visual problems such as amblyopia or loss of vision, neurological problems etc. If the dots fail to disappear, try again when you are in a "better mood" (disappearance increases with euphoria), or at a different time of day.
5. Reversible Sphere: Horizontal: Yoram Bonneh.
The apparent rotation of the sphere reverses direction, but with a very long period compared to other rivalry figures. This reversible figure also shows considerable plasticity, since the cycle shortens as one's experience with the pattern grows.
6. Reversible Sphere: Vertical  : Yoram Bonneh.
7. Dancer Silhouette: A popular reversible figure has appeared recently in the Australian press. This was invented by Nobuyuki Kayahara and has provoked enormous reaction on the web, along with some ill-informed criticism. Not many commentators have recognised this as an example of perceptual rivalry and none that I have seen have noted our original suggestion that links perceptual rivalry to interhemispheric switching. It is ventured that a clockwise spinning dancer indicates a right hemisphere in control; vice versa for the left hemisphere. This is consonant with our  thesis that the opposite percepts represent  opposite hemispheres and goes a step further  by attributing  one hemisphere to  a particular direction of motion.  dancer.   We were able to do this recently for plaid motion rivalry, where the component, "sliding" percept is apparently a right hemisphere phenomenon, whereas the left hemisphere percept is the coherent, "diamonds moving upwards" ( see 15 below).
8.Eight Reversible Spheres:  Do you see them all spinning and switching together? Or are the directions or spin and time of switches different for different spheres? I would be very interested in your answers to these questions.    Note that this one may require a click on Reload to get going.
9. Dali's Slave Market/Voltaire:
Salvador Dali was fascinated by perceptual rivalry and has dozens of paintings that utilise this aspect of perception. He seems to have realised just how ambiguous sensory input often is. I have chosen this painting because I saw the original in Florida and was unable to see the bust of Voltaire at first. It became apparent when I changed my distance from the painting. If you have trouble seeing Voltaire, move away from the screen to make his head have more suitable spatial frequencies to balance the slave-girl heads.
10. Mona Lisa:
The enigmatic smile of Leonardo's La Gioconda has intrigued viewers for centuries. Her different "looks" alternate back and forth. Another example of perceptual rivalry?
11. Dale Purves' Illusion:
    Believe it not, both surfaces have the same brightness!!
    Dale has stressed the ambiguity that exists between the intrinsic light/dark nature of an object's surface and its incident illumination.
    Is it white-looking because it is made of Carrara marble, or is it a more dingy stone that is brightly illuminated?
    It is impossible to tell from inspection what are the relative contributions of these two things......the intrinsic properties of the object ....and its     incident illumination. So we have to resort to other information that relies heavily on our past experience with illumination, shapes of objects, shadows, brightness of materials etc.
This illusion is very hard to "shake" but its magnitude may fluctuate in time, like the other ambiguous perceptions. I would appreciate feedback from observers about this possibility.
12. Dale's Colour Cross:
Also from Dale Purves.
Have a look at the joining region where all the arms of the cross meet. Most people see the joining region on the Left as a dark grey, almost purplish colour, contrasting with the corresponding region on the Right, which looks yellow.
Yet they are both physically identical!
You can verify the identity by a stepwise removal of the background until only the joining regions are showing.
13. Logvinenko's Illusion:
In the same class as Dale Purves' illusion, this one is even more astonishing. It was met with disbelief by my research group....until they masked off the surrounding regions.
1 and 2 have the same brightness, as can be checked in the masked version on the left.
This is in the same class as Dale Purves' figure. The misperception may arise from our experience of folded structures like curtains and drapes, where we are misled by applying a rule about the constancy of the drapes' brightness and colour, even in the depths of shadow.
14. Adelson's Shadow-checker Illusion:
This is in the same class as  10, 11 and 12, arising fom the inescapable ambiguity of colour.
15. Plaid Motion Rivalry:
This is our latest object of study. The switch rate between the coherent ("diamonds") perception of a plaid and the perception of two transparent, independently-moving gratings (the component or "slidings" percept) is correlated with switch rate on binocular rivalry and Bonneh's motion-induced blindness. In addition, the hemispheric assignment of each percept is more reliable than it is in binocular rivalry. The coherent percept seems to be associated with the left hemisphere while the component percept is associated with the right. For this reason, there is a very good correlation between mood and the ratio of the time spent in each percept.

Terminak Display of Plaid Motion Rivalry Click here for plaid motion rivalry display
This works in Netscape and Explorer, but not in Safari.

Notes on getting the best display:
1. The moving displays, especially 4, 5, 6, and 7, will perform best if you do not have other greedy software (e.g. Eudora, Powerpoint) running in the Background.
2. Another way to get good performance of the display is to save it as a Favourite in Explorer and then run it from your browser directly instead of from the web.
If you have other software running and rely on the web for the display, you may find that it jogs or stops and starts instead of running smoothly.
3. You may have to click on Reload to get Display 7 moving.

Volunterering for Perceptual Rivalry Research:  If you enjoyed these demonstrations and would like to participate actively in the enjoyable and topical area of resarch, please contacy Bonnie Sheppard  at the University of Queensland, email You will be paid for your participation. Since we are investigating the effect of mood and mood disorders on perceptual rivalry, we particularly welcome volunteers who may have altered moods.