Topography of the food-reinforced key peck and the source of 30-millisecond interresponse times.
Those ultra-short IRTs on ratio schedules are just the bird's bill bouncing off the key, not true new pecks.
01Research in Context
What this study did
Smith (1974) watched pigeons peck a key for food on ratio schedules. High-speed film caught every bill stroke. The goal was to see why very short IRTs, around 30 ms, pile up on these schedules.
What they found
The short IRTs are not new responses. The bird's bill can arc back and hit the key again within 50 ms. The key re-trips before the bird lifts its head. Topography stays the same; only the contact point moves a hair.
How this fits with other research
Hart et al. (1968) saw messy IRT scatter under VI schedules. Smith (1974) now shows that on ratio schedules the mess is mechanical, not learned. The two papers bracket how schedule type shapes IRT data.
Wolchik et al. (1982) found that unsignaled half-second delays also inflate short IRTs. Together the studies warn: both apparatus bounce and delay contingencies can fake rapid response bursts.
Gentry et al. (1980) later proved you can purposely shape peck duration with differential reinforcement. F's work sets the baseline: without such shaping, topography stays locked.
Why it matters
Before you count 30-ms IRTs as skilled acceleration, check your equipment. Lower key sensitivity, add a brief hold, or use an IRT> criterion. This guards against reinforcing bill-bounce artifacts and keeps your rate data clean.
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02At a glance
03Original abstract
High-speed photography of key pecking revealed that the arc described by the upper bill as a pigeon closes its beak is capable of operating a Lehigh Valley pigeon key set at 8 to 14 g. Arc-produced switch closure follows initial switch closure in less than 50 msec. When birds were trained on ratio schedules, the probability of interresponse times (IRTs) shorter than 50 msec exceeded 0.30. Interval-trained birds produced a much lower probability of short-IRTs. When the schedules were reversed, there was only weak evidence of a reversal in the probability of short IRTs. A temporal analysis of topographic features observed in the original photographs failed to reveal differences between ratio and interval pecking topography. It appeared that only the point of contact with the key differed between subjects trained on the two schedules. It was concluded that only the locus, but not the topography, of the food-reinforced key peck was modified by the schedule of reinforcement.
Journal of the experimental analysis of behavior, 1974 · doi:10.1901/jeab.1974.21-541