When light hits the retina, visual information is translated into a cascade of nerve impulses sending signals deep into the brain. It is here, in the brain's visual cortex, which resides in the occipital lobe at the back of the skull, that these signals are interpreted and give rise to perception. But the visual system has limited capacity and cannot process everything that falls onto the retina. Instead, the brain relies on attention to bring details of interest into focus so it can select them out from background clutter.Scientists had known for some time that attention to visual details increased the firing of neurons that responded to those details. What they didn't realize until now is that attention also reduces background noise, improving the clarity of the signal:
The findings of the Salk researchers, published in the September 24, 2009 issue of the journal Neuron, reveal that the uptick in the firing rate is only a small part of the story. "What we found is that attention also reduces background activity," says postdoctoral researcher and first author Jude Mitchell, Ph.D. "We estimate that this noise reduction increases the fidelity of the neural signal by a factor that is as much as four times as large as the improvement caused by attention-dependent increases in firing rate. This reduction in noise may account for as much as 80% of the attention story."The study reminds us that attention is our window into the world. The results seem to support the following practical observations:
- When you present visual information, less is better if you want more control over what your audience notices.
- The old saying is true: We see what we want to see. The rest is noise.