Monday, July 16, 2012

Nature’s Brains, Part 1

July 8, 2012
Bob Fiske

Nature’s Brains, Part 1

 "But the old crow comforted me, saying, 'If you only had brains in your head you would be as good a man as any of them, and a better man than some of them.  Brains are the only things worth having in this world, no matter whether one is a crow or a man.'  After the crows had gone I thought this over and decided I would try hard to get some brains."
     -- The Scarecrow in: L. Frank Baum, The Wonderful Wizard of Oz, 1900

I have a little story to tell.  I went on a walk in the neighborhood I grew up in on a sunny morning in July, 2012.  This is a section of Los Angeles that is a little hilly.  Most of the houses have foundations that are above street level.  All of the streets curve both up and down and to the side.

I came around a curve and caught sight of a clear plastic bird feeder mounted on the outside of one house’s large living room window.  It was shaped like a little house with an opening in front and a sunken floor for holding the bird seed.  Its unusual position—in the middle of a large plate glass window—was what probably attracted my attention initially, but it took only a fraction of a second to notice the little, brown sparrow inside of it.  Standing sideways to my vantage point it leaned forward and down to peck at the supply of seeds.

I stopped, and so did the sparrow.  I did not want to disturb the bird, I wanted to watch it eat.  But the sparrow stood (sideways to my view) and waited.  It waited for me to walk by and away.  I did not.

This little bird stopped its eating because a large animal—a human being—came into view.  The large animal was close enough to pose a potential threat, and so the bird shifted to defensive behavior.

"Close enough".  That is noteworthy.  The house sat on a rise behind a retaining wall.  I was perhaps 15 feet from the front of the house.  Moreover, the base of the house was at least five feet above my eye level.  And the plastic bird feeder in the middle of the window was an additional eight feet above that.  So that little bird sat on a perch 18 feet above the ground on which I stood and 15 feet away.  Or (thanks to the Pythagorean theorem) there were a good 23 feet between my perch and the bird’s.

And, yet, that sparrow registered me as a threat.

Of greater interest to me was how the bird reacted to this threat.  It watched me.  Remember, a sparrow’s eyes are on the sides of its head.  This is generally true for prey animals.  So, standing sideways, it had a direct view of me.  It made tiny little movements up, down and side-to-side with its head.  This is an understandable response to threat.  Not only was it watching me, but it was scanning the environment, the better to assess if there might be other threats.  The better to assess possible escape routes.

I imagine that this sequence of behaviors—feed, detect, assess, and prepare for lifesaving flight—is a normal affair for a foraging, prey animal such as a sparrow.  Its brain is wired with strategies for preserving its existence.  More about that later.  Yet, I wanted to see if I could maintain a non-threatening status long enough that the bird would relax its threat response and return to eating.  So, I stopped.  I stood still.

I stood motionless, and the sparrow scanned with its little head movements.  I am a patient person.  I waited.  After nearly a minute the bird made a little forward-bobbing movement with its beak.  Just a little movement.  It wanted to return to eating.  But the parts of its brain responsible for the defensive scanning and preparation for flight overrode that impulse.

These impulses, feed, detect, assess and prepare for flight, seem to have independent existences in the brain.  Like a committee formed of department managers, they must come together and negotiate.  Who is going to dominate?  Who will take control of the bird’s behavior?  That all depends on the current conditions, of course.  If a potential threat appears, then the defensive managers win the negotiation.  If the threat fails to materialize, then the feeding manager garners more power in the negotiation.

I could see these internal negotiations taking place—from something as insignificant as a tiny forward-bobbing motion of the head.  I knew that I could affect the outcome of the negotiation simply by continuing to wait without moving.

Another 15 or 20 seconds.  Did I see another forward head movement?  Perhaps.  Now it was well over a minute since our encounter had begun.  There, definitely.  A forward head movement, followed by more scanning.  Another quarter of a minute.  A forward movement, this time more pronounced.  Not the actual eating of the bird seed on the feeder’s floor, but a clear indication that the impulse to feed had not been completely suppressed.

And so it went.  I believe that it was coming up on two minutes.  Finally I saw a deep bowing of the head.  The bird’s beak appeared to make contact with the seed.  Nervously the sparrow resumed its eye-scanning.  Then it tapped its beak back to the bird seed.  After a short pause it did that again.  And again.

I was rewarded by my frozen stance.  As I expected, I could outwait the nervous behavior produced by the little sparrow’s marvelous little brain.

No comments:

Post a Comment