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
-- 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.
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