Failure to find positive key-press contrast for milk reinforcers using a within-session procedure.


Rats pressed keys for sweetened condensed milk delivered by multiple schedules. Component duration varied from five seconds to 16 minutes. Positive contrast did not occur for any duration. That is, the rate of responding emitted during a variable interval component of a multiple schedule was not greater when the other component was extinction than when it… (More)
DOI: 10.1016/0376-6357(92)90021-5