Effects of food-pellet size on rate, latency, and topography of autoshaped key pecks and gapes in pigeons.
Bigger reinforcers make autoshaped responses faster, sooner, and slightly different in form.
01Research in Context
What this study did
The team worked with pigeons in an autoshaping set-up. Birds saw a lit key followed by food.
They varied only pellet size: small vs. large. Then they counted key-pecks, timed how long birds waited, and filmed how wide the beak opened.
What they found
Big pellets made pigeons peck faster and start sooner. The same birds also opened their beaks wider when the pellet was large.
The changes happened every time they switched pellet sizes, so the effect was reliable.
How this fits with other research
Reed et al. (1988) saw the same speed-up in rats: bigger food made lever presses faster. Their rats also paused longer after each treat, a detail O et al. did not measure.
Van Houten et al. (1980) showed you can shape how a peck looks by requiring longer or shorter contacts. O et al. prove you can also tweak topography just by changing pellet size—no extra training needed.
Corrigan et al. (1998) found that unsignaled delays cut peck rates because birds stared at the hopper instead. O et al. flip that coin: more food in the hopper pulls birds back to the key faster and makes them open wider.
Why it matters
For BCBAs, reinforcer size is a dial you can turn. A bigger edible, longer iPad clip, or extra bubbles can boost correct responses and shorten latencies without new teaching steps. Watch for satiation, but start sessions with a generous portion to lock in quick, crisp responses.
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02At a glance
03Original abstract
Four pigeons responded under autoshaping contingencies in which different conditional stimuli (red or green keylights) were associated with unconditional stimuli of different magnitudes (large or small food pellets) over successive trials within a session. Both topography (beak opening or gape) and strength (rates and latencies of key pecks and gapes) of responding during the conditional stimuli depended on the magnitude of the correlated unconditional stimulus. Key-peck and gape rates were higher and latencies were shorter in large-pellet trials than in small-pellet trials. Gape amplitudes varied directly with pellet size, although conditional and unconditional gapes were larger than either pellet. These findings were replicated when the key colors were presented either on one or two keys and after reversals of the color-size correlations. Because the unconditional stimulus was varied through pellet size, magnitude was not confounded with food-access duration or quality. These results demonstrate the effects of the magnitude of the unconditional stimulus, in that rates and latencies of both key pecks (which are directed movements toward the key) and gapes (which are independent of the bird's position and key properties) varied with pellet size. Gape measures were unique in that two dimensions (response strength and topography) of a single response class varied simultaneously with magnitude.
Journal of the experimental analysis of behavior, 1996 · doi:10.1901/jeab.1996.65-21