An operant discrimination task allowing variability of reinforced response patterning.
Reinforcing "be different" fails under free-operant conditions; add brief timeouts to make variability pay.
01Research in Context
What this study did
Quilitch et al. (1973) worked with pigeons in a small lab chamber.
The birds could peck four keys in any order.
If the four-peck sequence differed from the last 50 patterns, grain arrived.
The team wanted to see if paying for variety would keep the birds flexible.
What they found
Instead of staying varied, each pigeon froze into one favorite sequence.
The pattern repeated even though it no longer earned the most food.
Reinforcing variability alone did not stop stereotypy.
How this fits with other research
Morris (1987) later cracked the puzzle.
That study showed the 1973 setup accidentally rewarded fast repeats.
By adding a brief pause after each four-peck set, Morris (1987) tripled reinforcement and produced high variability.
The new method simply updated the old one.
Sachs et al. (1969) had already shown that steady reinforcement tightens response location.
Quilitch et al. (1973) asked the next question: can we loosen sequence rigidity by paying for difference?
The answer was "not with this free-operant layout."
Schwartz (1982) confirmed that once pigeons lock in a four-peck chain, the pattern sticks across schedules.
Why it matters
If you want flexible responding, do not rely on "be different" alone.
Insert a short pause or use discrete trials, as Morris (1987) showed.
Check that your reinforcement setup is not accidentally feeding speed or repetition.
A quick timing tweak can turn a stereotypy trap into a variability engine.
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02At a glance
03Original abstract
Five pigeons were trained to perform a discrimination task allowing variability of reinforced response patterning. The task consisted of moving a stimulus light within an 4x4 matrix of lights from the top left position to the bottom right position by pecking on two keys in succession in order to obtain a reinforcement. A peck on one key moved the light one position to the right and a peck on the other key moved it one position down. After preliminary training on alternating fixed-ratio 3 schedules of reinforcement, the birds could peck on either key in any order, but more than three responses on a key resulted in a blackout followed by the return of the stimulus light to the start position. Results indicate that initially the birds used a wide variety of response patterns to obtain reinforcement, but with continued practice, response patterns became more stereotyped.
Journal of the experimental analysis of behavior, 1973 · doi:10.1901/jeab.1973.20-1