Perceptual and Memory Illusions

We sometimes tend to forget important information and at times remember things wrongly. Moreover, the various perceptual illusions that we encounter make us doubt the capability of our own senses. Do these occurrences mean that our perceptual and memory systems are unreliable and flawed? I certainly do not think so. In a world where survivability is catered to the fittest, our perception and memory has evolved and adapted to the ever-changing environment. This adaptation has enabled us to have a survival advantage. Therefore we should not see these systems as flaws but rather effective adaptive mechanisms.

Firstly, we see things that are not "real". These things are what we call perceptual illusions and the reason they occur is due to our unique way of perception. We rely heavily on our knowledge and experience when it comes to understanding that an object is of the same size, shape or colour regardless of the different sensory inputs that we receive (perceptual constancy) (King, 2008). These various collections of knowledge and experiences can be organised into different models to explain different constancies (Gregory, 1968). This reliance on experience and knowledge serves us humans well as we can process information rapidly with little sensory input available. For example, through experience, we'll know how exactly an orange will look like. Consequently we can identify an orange using fewer cues. This is why we can achieve an effective information transmission rate of 15 bits/second with little information (Miller,Bruner&Postman, I954). This effective form of perception, I believe, will enable us to allocate more resources to other vital processes instead. However, the limitations of using such models can be seen in perceptual illusions. Many perceptual illusions are attributed to the selection of the wrong models (Gregory, 1968). However, in my opinion, such a flaw arising from this perception is very minor and a small price to pay compared to what perceptual constancy has enabled us to do.

Moreover, many perceptual illusions are a product of evolutionary adaptions of perception. Let's take the example of an illusionary contour (fig 1) where we tend to "see" a square even though it is not present. This illusion is attributed to the evolution of perception in edge detection. To perceive the edges better, we tend to enhance the differences between the light and dark regions. This developed tendency to enhance the differences between various shades, gives rise to the illusionary contour (Medin, Ross & Markman, 2005). To perceive sharper images is definitely an acquired advantage as we can be better aware of our surrounding. This again proves the adaptive nature of perception.

Moving on to memory, the fact that memories are reconstructable, may take the value away from memory. However, this reconstructive nature is in fact beneficial and crucial to our adaptation. Let's take