Bullock, C. E. & Hackenberg, T. D. (2006).
Second-order schedules of token reinforcement with pigeons: Implications for
unit price.
Journal of the Experimental Analysis of Behavior, 85, 95-
106.
Four pigeons were exposed to second-order schedules of token reinforcement, with
stimulus lights serving as token reinforcers. Tokens were earned according to a
fixed-ratio (token-production) schedule, with the opportunity to exchange tokens for
food (exchange period) occurring after a fixed number had been produced
(exchange-production ratio). The token-production and exchange-production ratios
were manipulated systematically across conditions. Response rates varied inversely
with the token-production ratio at each exchange-production ratio. Response rates
also varied inversely with the exchange-production ratio at each token-production
ratio, particularly at the higher token-production ratios. At higher token-production
and exchange-production ratios, response rates increased in token-production segments
closer to exchange periods and food. Some conditions were conducted in a closed
economy, in which the pigeons earned all their daily ration of food within the
session. Relative to comparable open-economy conditions, response rates in the
closed economy were less affected by changes in token-production ratio, resulting
in higher levels of food intake and body weight. Some of the results are consistent
with the economic concept of unit price, a cost-benefit ratio comprised of responses
per unit of food delivery, but most are well accounted for by a consideration of the
number of
responses required to produce exchange periods, without regard to the amount of
reinforcement available during those exchange periods.
Key words: token reinforcement, second-order schedules, fixed-ratio schedules,
unit price, key peck, pigeons