If you're like me, it doesn't take much time looking at a cloud to see a duck or at the irregular grain of wood to see a face. In fact, one of the most basic perceptual principles is the gestalt effect: the grouping of elements together into a familiar, whole form rather than a collection of separate parts. The image to the left consists of only discrete dots, each of which contains virtually no information at all. But the perception is much more meaningful: that of a human form. The dots even suggest a behavior: that it is safe to cross the street. And this persistent process of constructing more from less goes beyond producing an understanding of visual images and street signs. It creates our understanding of the self as well.
Most take for granted the sovereignty of the self, assuming it to be a personal ‘head of state,' the principal author of your thoughts and actions. The feeling that a single, unified, enduring self inhabits the brain - the "me" inside me - is compelling and appeals to intuition, as do all neural constructions once they are made.
Alternatively, however, Hume described the self as a ‘bundle of perceptions.' In bundle theory, inherently fleeting experiences are woven together by memory to create the illusion of a continuous entity. This entity becomes more organized and realized on our psychological landscape than its source. In this way, raw, discrete experience casts a shadow that we embellish as the experiencer. Here, the self is not actually an entity but, rather, an idea...a construction.
As an example, consider the image below. It consists only of 8 black circles on top of which appear to be the corners of a Necker Cube. Though there are no white lines connecting the corners of the cube, they must be there, so your brain manufactures them. These illusory lines are called subjective contours. By analogy to bundle theory, each corner of the Necker Cube represents an experience or perception. Your unified self is a manufactured fusion of these discrete elements...a kind of subjective contour. And like all neural constructions, it's convincingly, stubbornly, undeniably, persistently real, taking center stage from the actual experiences woven together in the gestalt effect.
However, the connecting lines of the necker cube exist only under the assumption that the cube is in front of the black dots. If you assume that the cube is behind a white surface with 8 holes cut into it, the connecting bars no longer make sense and are no longer fabricated. (Try it. It might take a minute for your brain to make the shift, but once it does the effect is quite strong.)
Likewise, the merger of perceptions that constitutes the self can dissolve if neural conditions change, as in split-brain or Dissociative Identity Disorder (formerly Multiple Personality Disorder). Or apply magnetic pulses to your left angular gyrus in the parietal lobe and you may feel the presence of a shadowy ‘self' behind you. The same stimulation to the right angular gyrus and you may perceive your ‘self' as floating above your body, looking at it from above. There is also evidence that blocking input to the posterior, superior parietal area can eliminate the experienced distinction between self and other, a state that can be achieved through meditative practice. Because the self is a construction, it is quite malleable.
Arguably, the construction of a self is of survival advantage. For instance, an organism will likely run faster to evade a predator or catch prey if failure to survive means not only cessation of experience, but also the death of this intimate, meaningful entity. The self gives you a dog in the fight.
But excessive attachment to the concept leads to pain and suffering, a prime tenet of Buddhist philosophy (the world's most prevalent bundle-theory-friendly religion). Fortunately, meditative practice can, in time, cast the concept in a more healthy role...in a sense, recess the necker cube from the forefront to the background, eliminating the illusory connective contours. Doing so reduces the prominence of the secondary, enduring, constructed self and enhances ones experience of the primary, transient, subjective ‘experiencer'...your Self with a capital S.
What Einstein said of reality can certainly be edited to reflect our current understanding here: "[The self] is merely an illusion, albeit a very persistent one."