Info

Axon from sensorv

Axon from sensorv

A urn from motor ^Jfcrcnl !> ncurou

VülLtKll roen

A urn from motor ^Jfcrcnl !> ncurou

VülLtKll roen

The reflexive nature of perception and behavior points to a still deeper problem at the center of a debate that has persisted since the Stoic and

Epicurean philosophers were at each other's throats over this issue in ancient Greece: Does the way brains work allow us to act freely, or is what we think and do fully determined? The evidence discussed here and in previous chapters inevitably bears on this vexing question. Based on empirically determined sensory circuitry, the brain generates behavior that works surprisingly well in a world that our senses can't tell us about directly. This way of producing perceptual content and behavior is very different from our subjective impression of what is going on. Everyday experience suggests that our brains (a stand-in for the "me" or the "I" that we take for granted) analyze stimulus features and represent these features, and that we then make decisions about how to act based on representations of the world "as it really is." But if brain activity and its perceptual and behavioral consequences simply reflect neural associations created by accumulated phylogenetic and ontogenetic experience, then a wholly empirical understanding of brain function comes down squarely on the side of determinism. In this framework, terms such as inferences, decisions, and choices are apt descriptors of our subjective sense of the way we relate to the world, but not of any underlying brain function.

To sum up how brains seem to work, the circuitry of nervous systems such as ours has evolved to contend with one fundamental challenge: How to generate useful perceptions and behaviors in response to a world that is unknowable directly by means of sensory stimuli. The strategy that has emerged to deal with this problem is governed by history, not logical principles or algorithms. Based on feedback from the empirical consequences of behavior, accumulated information about operational success is realized over evolutionary time in inherited neural circuitry whose organization is then modified to a limited extent by individual experience. Accordingly, our perceptions never correspond to physical reality despite the fact that they provide successful operational guides to behavior. The evidence that supports these conclusions is the ability to predict many otherwise puzzling perceptual phenomena using databases that serve as proxies for aspects of accumulated human experience.

These ideas about what we perceive, what we do as a result, and ultimately what we are in consequence may be anathema to neuroscientists committed to a rationalist perspective of brain function, or to anyone who has difficulty disengaging from the subjective sense we have of the world and our relation to it. But if the evidence continues to support a wholly empirical interpretation of how brains work, we will simply need to pursue brain function and structure in these terms, perhaps gaining in the process a clearer and more useful conception of ourselves and our place in nature.

Suggested reading

Adelson, E. H. "Light Perception and Lightness Illusions." In The New Cognitive Neurosciences, 2nd edition, edited by M. S. Gazzaniga. Cambridge, MA: MIT, 2000. 339-351. Allman, J. M. Evolving Brains. New York: W.H. Freeman, 1999.

Barlow, H. B. "The Neuron Doctrine in Perception." In Cognitive Neurosciences, edited by M. S. Gazzaniga. Cambridge, MA: MIT Press, 1995. 415-436.

Berkeley, G. Philosophical Works Including Works on Vision, edited by M. R. Ayers. London: Everyman/ J. M. Dent, 1975.

Blake, R. "A primer on binocular rivalry, including current controversies." Brain and Mind 2 (2000):

Was this article helpful?

0 0

Post a comment