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J Exp Anal Behav. 1985 March; 43(2): 257–264.
PMCID: PMC1348135

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.


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.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Blough DS. Visual search in the pigeon: hunt and peck method. Science. 1977 May 27;196(4293):1013–1014. [PubMed]
  • Blough DS. Pigeon perception of letters of the alphabet. Science. 1982 Oct 22;218(4570):397–398. [PubMed]
  • Sands SF, Wright AA. Monkey and human pictorial memory scanning. Science. 1982 Jun 18;216(4552):1333–1334. [PubMed]
  • Schwartz B. Development of complex, stereotyped behavior in pigeons. J Exp Anal Behav. 1980 Mar;33(2):153–166. [PMC free article] [PubMed]

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