Foster, T. A. & Hackenberg, T. D. (2004).
Unit price and choice in a token-reinforcement context.
Journal of Experimental Analysis of Behavior,
81, 5-25.
Pigeons were exposed to multiple and concurrent second-order schedules of token
reinforcement, with stimulus lights serving as token reinforcers. Tokens were
produced and exchanged for food according to various fixed-ratio schedules,
yielding equal and unequal unit prices (responses per unit food delivery). On
one schedule (termed the standard schedule), the unit price was held constant
across conditions. On a second schedule (the alternative schedule), the unit
price was either the same or different from the standard. Under conditions with
unequal unit prices, near-exclusive preference for the lower unit price was
obtained. Under conditions with equal unit prices, the direction and degree of
preference depended on ratio size (number of responses per exchange period).
When this ratio differed, strong preferences for the smaller ratio were
observed. When this ratio was equal, preferences were nearer indifference.
Response rates on the multiple schedule were generally consistent with the
preference data in showing sensitivity to ratio size. Results are discussed in
terms of a unit-price model that includes handling and reinforcer immediacy as
additional costs. On the whole, results show that preferences were determined
primarily by delay to the exchange period.
Key words: choice, fixed-ratio schedules, second-order schedules,
token reinforcement, unit price, key peck, pigeons