Am I smarter than a bird? What susceptibility to optical illusions can tell us about the evolution of perception

To speak plainly, humans are innately greedy. It is in our evolutionary history that we seek out the biggest rewards with the smallest risks. Even now, in a modern age when competition for resources like food are (for the most part) not quite as harsh as pre-polite society, we actively pursue outcomes that best advantage our evolved needs such as eating. To put this into a contemporary perspective, imagine you’re out to eat with a few classmates and the sharing pizza arrives at the table — everyone's fingers are itching to grab the biggest slice.  

So, how come we sometimes guess wrong? We can turn to the Ebbinghaus illusion to help us illustrate this. Previous scientific research from years past has shown that us humans are comparable to guppies in our susceptibility to this optical trick. Flattering, I know.   

The illusion consists of two circles of equal size; one surrounded by larger dots so that it looks smaller than it’s twin which is surrounded by small dots. For humans, this phenomenon is linked to global processing which suggests that our preference leans towards viewing stimuli as a whole rather than taking to time to process each individual aspect; explaining why we quickly conclude that one circle is actually larger. Guppies boast this same preference, repeatedly choosing food which was enclosed within smaller dots. Even across vastly different ecological niches, susceptibility to this optical illusion is present.  

How does this compare to other species? Are we perceptually similar to other animals besides fish?  

Well, recent scientific studies have discovered that humans are certainly not comparable to birds — in fact our winged counterparts seem a lot more difficult to dupe. When presented with the same illusion, this time replacing fish flakes for millet seeds to suit the dove’s tastes, we see no clear susceptibility at a group level. Sure, some doves leaned the same way in their choices as humans and guppies, whilst some chose the complete opposite, and some made choices unaffected by the perceptual differences at all suggesting alternative, perhaps more detail oriented perceptual strategies in doves.  

This resilience to surrounding context could be accounted for by the binocular vision in birds and their familiarity with attention to detail since pecking at their minuscule food requires more precision than we might use to grab our pizza slice.