Here is more information from Dr. David Nowell, M.D. about the role of the brain’s Reticular Activating System (RAS):
What is this RAS?
Q: I had one question which I hope you can answer for me. I was led to believe that anytime my brain was processing information (thinking, daydreaming, writing, etc.), the RAS switch would flip and shut off my ability to retain what is being said. Is this true? What’s the role of the Reticular Activating System (RAS) in attention and focus?
A: Thanks for a really good question. OK here goes. Our RAS serves as a gating mechanism to screen out most incoming sensory information. Well, to partially screen it out. If something important (relevant, dangerous, interesting) presents itself, the RAS “gate” allows the sensory information (tactile, auditory, visual) on through to the higher cortical areas for actual processing.
So in a sense, a student is “hearing” everything in a busy classroom: the air conditioner, the pencil sharpener, the students talking behind him, the teacher lecturing, the voices out in the hallway.
But he is only “listening” to that which is relevant/ important/ interesting.
And the distinction between relevant/not relevant is made at two levels.
Level 1 distinction (bottom-up)
The the RAS operates outside our awareness. So if a spider crawls across my foot, the RAS bumps that sensory information up and through to my decision-making cortex. I might not have “thought” about my foot for 20-30 minutes, but the RAS allows the spider-info to take priority. It’s important, or salient.
If someone out in the hall says “blah blah David blah blah David Nowell,” my RAS will alert me to this incoming information. Literally, for a second or two everything else will fall away as my attentional resources divert to this interesting/important conversation out in the hallway.
Source: Dr. David Nowell, M.D.
Image Source: Patrick J. Lynch, medical illustrator; Zlir’a
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