Fig. 10.

Mean number of large-reinforcer choices per 10-trial session for 3 pigeons in a token-based self-control procedure as a function of exchange-delay conditions. Delays to the exchange periods were either unequal and shorter for the small-reinforcer option (UD) or equal for both options (ED). Data are from the final 10 sessions per condition; error bars reflect the range of values contributing to the mean. From Jackson & Hackenberg (1996). Copyright 1996, by the Society for the Experimental Analysis of Behavior, Inc. Reprinted with permission.