An infrared system for the detection of a pigeon's pecks at alphanumeric characters on a TV screen: the dependency of letter detection on the predictability of one letter by another.
Stimulus history, not just the current item, controls choices in pigeons and probably people.
01Research in Context
What this study did
The team trained pigeons to peck at letters on a TV screen. An infrared beam tracked each peck.
The birds earned food only when they pecked the target letter T. Sometimes the letter F came before T. The chance that F predicted T changed across sessions.
What they found
When F usually came before T, the pigeons pecked T faster and more often. When F rarely came before T, accuracy dropped.
The birds learned to use the earlier letter as a cue, even though only the final letter paid off.
How this fits with other research
Poling et al. (1977) showed pigeons can keep a two-part cue in mind for ten seconds. The new study adds that even weak parts of a cue chain can matter.
Coe et al. (1997) found pigeons pick the least frequent stimulus, but memory fades fast. Here, the predictive link, not just frequency, drove choice.
Corrigan et al. (1998) proved pigeons see biological motion on screens. Together, these papers show screen-based tasks can test many kinds of stimulus control.
Why it matters
Your clients also respond to what came before, not just what is present now. If you want a child to pick the red card, check what card showed last. Change the early cards and you can speed up or slow down the correct choice. Try adding or removing a reliable cue before the target stimulus and watch how behavior shifts in the next session.
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Run a probe: present the target S+ alone, then after a formerly neutral stimulus, and chart any change in latency or accuracy.
02At a glance
03Original abstract
Three pigeons pecked at letters of the alphabet and at the symbol "?" displayed on a computer-driven cathode ray screen. A 4 by 4 matrix of infrared emitting and detecting diodes and associated circuitry identified the location of a pigeon's responses to the screen. Responses at the target letter T were probabilistically reinforced with food whenever T appeared in a string of three letters in the middle of the screen. Responses at the symbol "?" appearing below this string were probabilistically reinforced whenever T did not appear. The letter F anywhere in the three-character string either strongly predicted the occurrence of the target letter T, in two conditions, or predicted its nonoccurrence, in a third. This manipulation of the frequency with which the familiar letter F predicted T was shown to change the function relating probability of a correct peck at the symbol "?" to the number of Fs in the string. This effect may be interpreted as an instance of the phenomenon where an organism's acquired knowledge changes what it sees.
Journal of the experimental analysis of behavior, 1985 · doi:10.1901/jeab.1985.43-257