A preliminary analysis of the dynamics of the pecking response in pigeons.
Pigeon pecks are force-variable and asymmetrical—set force criteria well above 35 g and expect waveform noise.
01Research in Context
What this study did
Researchers wired a pigeon key to a force transducer. They wanted to see what a peck actually looks like in terms of pressure over time.
Each bird worked alone. The team recorded thousands of pecks and plotted the tiny force waves.
What they found
Peck force is messy. The lines jump high, dip low, and sometimes show two bumps instead of one.
Many pecks blast past the 35-gram mark needed for food. That means you must set the trigger well above 35 g or you will miss valid responses.
How this fits with other research
Gentry et al. (1980) later showed you can shape how long a peck lasts, but the bird's old style keeps pulling the response back. Force and duration both resist change.
Duncan et al. (1972) found two kinds of pecks: short ones under negative contingencies and longer ones under positive. The wobbly force curves seen here may reflect those two classes.
Kono (2017) moved from force to space, showing that pigeons also drift their peck location around the key under fixed-interval schedules. Micro-variability shows up in every dimension.
Why it matters
When you build an apparatus or write a software threshold, leave plenty of room above 35 g. Expect odd, double-humped waves instead of neat spikes. If you later try to shape a cleaner form, remember that both force and location have built-in noise that you must work against.
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02At a glance
03Original abstract
The pecking response of pigeons is usually measured by a transducer that senses the presence or absence of a response. Typically, the response force as a function of time has not been accurately measured. Data were collected using a transducer specially designed to record the waveform of the pecking response in pigeons. Each response on the target surface of the transducer was reinforced and followed by a blackout. The response was stored on an oscilloscope screen and the peak force and duration of the response were recorded manually from the oscilloscope screen. The mean peak force of the response substantially exceeded the minimum criterion for reinforcement of 35 g (0.343 Newtons) of force. Photographs of the waveform of pecks on the transducer showed great variability in response force and demonstrated that the waveform produced by pecking the target surface was complex. The responses were frequently asymmetrical with the rise time shorter than the fall time, although no single verbal description could be applied to all of the waveforms. Bimodal peaks and double responses were observed and the first peck or response was usually larger than the second. A disadvantage of the transducer was that pecking produced oscillation of the transducer at its resonant frequency. In spite of this deficiency, the waveform of the peck was easily recognizable.
Journal of the experimental analysis of behavior, 1970 · doi:10.1901/jeab.1970.13-267