Monday, March 30, 2009

Time Travel, Perception, and Mind-wandering

Today's post is dedicated to ideas promulgated by Bar's most recent article, "The proactive brain: memory for predictions."

Bar builds on the foundation of his former thesis, namely that the brain's 'default' mode of operation is to daydream, fantasize, and continuously revisit and reshape past memories and experiences. While it makes sense that traversing the internal network of past experiences is useful when trying to understand a complex novel phenomenon, why exert so much work when just 'chilling out' a.k.a. being in the 'default' mode? Bar's proposal is that this seemingly wasteful daydreaming is actually crucial for generating virtual experiences and synthesizing not-directly-experienced, yet critically useful memories of alternate scenarios. These 'alternate future memories' are how our brain recombines tidbits from actual experiences and helps us understand novel scenarios before they actually happen. It makes sense that the brain has a method for 'densifying' the network of past experiences, but that this happens in the 'default' mode a truly bold view held by Bar.

In the domain of visual perception and scene understanding, the world has much regularity. Thus the predictions generated by our brain often match the percept, and thus accurate predictions rid us of the need to exert mental brainpower on certain predictable aspects of the world. For example, seeing a bunch of cars on a road along with a bunch of windows on a building pre-sensitizes us so much with respect to seeing a stop sign in an intimate spatial relationship with the other objects that we don't need to perceive much more than speckle of red for a nanosecond to confirm its presence in the scene.

Quoting Bar, "we are rarely in the 'now'" since when understanding the visual world we integrate information from multiple points in time. We use the information perceptible to our senses (the now), memories of former experiences (the past), as well all of the recombined and synthesized scenarios explored by our brains and encoded as virtual memories (plausible futures). In each moment of our waking life, our brains provide us with a shortlist of primed (to be expected) objects, contexts, and their configurations related to our immediate perceptible future. Who says we can't travel through time? -- it seems we are already living a few seconds ahead of direct perception (the immediate now).