"r." coli

[From Bruce Abbott (950616.0955 EST)]

Rick Marken (950615.0900)

Here is a new version of the E. coli task that I will call R. coli because (I
think) all consequences of responses are completely _R_andom.

The task is (surprise) to keep a cursor aligned with a target. The subject
affects the cursor by pressing the mouse button (the response). The
consequence of this response is that the cursor moves to one of five
randomly determined positions on the screen. One of these five positions is
the target position.

So the result of any response is one of five randomly determined cursor
positions. The cursor remains in this randomly determined position until
another response occurs or until the position is changed (randomly) by an
external disturbance.

I believe (but, given my experience with E. coli I am not certain) that
there is no way for a reinforcement model to explain the results of this
R. coli experiment. All consequences of responding seem (to me) to be
completely random; there seems to be no systematicity . But I'm the one
who wants to show that reinforcement theory cannot explain control so I may
not be looking carefully enough. So I hope Bruce Abbott will take a shot at
developing a reinforcement model of R. coli.

This sounds like a variable-ratio schedule of reinforcement to me, Rick.
Let's call "being on-target" the reinforcer. Pressing the mouse button is
the response. Cursor movement is equivalent to a "feedback" beep that tells
you the button is working (like the click that is heard when a lever is
depressed far enough to operate the switch).

Situation 1: Cursor not on target.

Pressing the mouse button moves the target. Responses are emitted until the
cursor moves to target or the behavior extinguishes from lack of
reinforcement (whichever comes first). Occasional success reinforces
button-pressing, thus maintaining the behavior. Success is programmed on a
VR-5 schedule (on average, one in 5 responses will be reinforced, but the
actual number between two reinforcements varies randomly from 1 to some
upper limit.

Situation 2: Cursor on target.

You're "at the food-cup": no need to press the lever to obtain
reinforcement, because you've got it.

Disturbances remove you from the reinforcement condition, taking you back to
Situation 1 (just as eating the food in the cup takes the rat back to the
food-absent situation, necessitating further lever-pressing).

So much for r. coli. NEXT!

Don't worry Bruce; if
reinforcement theory can handle this one I'll go right back to the drawing
board again. I'm a glutton for punishment (and reinforcement).

I guess so. I'd keep the drawing board out. (;->

Regards,

Bruce