Effects of reinforcer magnitude on response acquisition with unsignaled delayed reinforcement

Sixteen rats received eight 1-h sessions of a tandem fixed-ratio 1 differential-reinforcement-of-other-behavior 30-s schedule with reinforcer magnitude at one or six food pellet(s) across groups of eight rats. The larger reinforcer magnitude established the lever press more effectively. First, mean schedule completions differed across groups, in terms of both their overall difference and in their increase across sessions. Second, whereas the larger reinforcer magnitude established reliable response acquisition in all eight rats by the end of the experiment, the smaller reinforcer magnitude only established reliable response acquisition in four of eight rats. The present results systematically replicate earlier findings obtaining more reliable response acquisition with unsignaled delayed reinforcement with greater food deprivation. Taken together, this work demonstrates the influence of motivational variables on response acquisition with unsignaled delayed reinforcement.

► Findings of response acquisition with unsignaled delayed reinforcement challenge conventional wisdom that immediate reinforcement is necessary to establish a novel behavior but little is known about the variables that influence the reliability of such acquisition.
► The present study systematically replicated Lattal and Williams (1997) by showing that larger reinforcer magnitudes enhance the reliability of response acquisition with unsignaled delayed reinforcement.
► Discussed is whether reinforcer magnitude exerted its influence through direct or indirect effects.