Just adding the right combination of grey and white crosses really screws things up, doesn’t it? It seems likely that the illusion comes from the perceived illumination (it probably helps that these are essentially Gabors).
There’s a nice reminder in Science this week that we are not the only animals subject to illusions – here is one in yeast (from the abstract):
We systematically monitored growth of yeast cells under various frequencies of oscillating osmotic stress. Growth was severely inhibited at a particular resonance frequency, at which cells show hyperactivated transcriptional stress responses. This behavior represents a sensory misperception—the cells incorrectly interpret oscillations as a staircase of ever-increasing osmolarity. The misperception results from the capacity of the osmolarity-sensing kinase network to retrigger with sequential osmotic stresses. Although this feature is critical for coping with natural challenges—like continually increasing osmolarity—it results in a tradeoff of fragility to non-natural oscillatory inputs that match the retriggering time.
In other words, a very non-natural stimulus – a periodic change in salt concentration – leads the yeast to instead ‘see’ a constant increase in the concentration. Pretty cool.
(via Kyle Hill)