How the brain pays attention

Listen to a preview of the Attention chapter on YouTube. Get the Brain Rules digital audiobook on Libro.fm.

What’s going on in our heads when we turn our attention to something? Thirty years ago, a scientist by the name of Michael Posner derived a theory that remains popular today. Posner started his research career in physics, joining the Boeing Aircraft Company soon out of college. His first major research contribution was to figure out how to make jet-engine noise less annoying to passengers riding in commercial airplanes. You can thank your relatively quiet airborne ride, even if the screaming turbine is only a few feet from your eardrums, in part on Posner’s first research efforts. His work on planes eventually led him to wonder how the brain processes information of any kind. This led him to a doctorate in research and to a powerful idea that’s sometimes jokingly referred to as the Trinity Model. Posner hypothesized that we pay attention to things using three separable but fully integrated networks of neural circuitry in the brain. I’ll use a simple story to illustrate his model.

One pleasant Saturday morning, my wife and I were sitting on our outdoor deck, watching a robin drink from our birdbath, when all of a sudden we heard a loud “swoosh” above our heads. Looking up, we caught the shadow of a red-tailed hawk, dropping like a thunderbolt from its perch in a nearby tree, grabbing the helpless robin by the throat. As the raptor swooped by us, not three feet away, blood from the robin splattered on our table. What started as a leisurely repast ended as a violent reminder of the savagery of the real world. We were stunned into silence.

In Posner’s model, the brain’s first system functions much like the two-part job of a museum security officer: surveillance and alert. He called it the Alerting or Arousal Network. It monitors the sensory environment for any unusual activities. This is the general level of attention our brains are paying to our world, a condition termed “intrinsic alertness.” My wife and I were using this network as we sipped our coffee, watching the robin. If the system detects something unusual, such as the hawk’s swoosh, it can sound an alarm heard brain-wide. That’s when intrinsic alertness transforms into specific attention, called phasic alertness.

After the alarm sounds, we orient ourselves to the attending stimulus, activating the second network: the Orienting Network. We may turn our heads toward the stimulus, perk up our ears, perhaps move toward (or away) from something. It’s why both my wife and I immediately lifted our heads away from the robin, attending to the growing shadow of the hawk. The purpose is to gain more information about the stimulus, allowing the brain to decide what to do. The third system, the Executive Network, controls what action we take next. Actions may include setting priorities, planning on the fly, controlling impulses, weighing the consequences of our actions, or shifting attention. For my wife and me, it was stunned silence, until one of us moved to clean off the blood.

So we have the ability to detect a new stimulus, the ability to turn toward it, and the ability to decide what to do based on its nature. Posner’s model offered testable predictions about brain function and attention, leading to neurological discoveries that would fill volumes.

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