Fractional punishment of fixed-ratio performance.

Key-peck responses of pigeons under a fixed-rate 60 (Exp. I) or fixed-ratio 99 (Exp. II) schedule of positive reinforcement were punished by response-dependent electric shock during a segment of the ratio. The punishing stimulus was scheduled in one of three locations: the first third of the ratio, the middle third, or the final third. At high shock levels, the different loci of punishment differentially affected the typical fixed-ratio performance pattern. Post-reinforcement pauses were lengthened by all punishment conditions but to a greater degree when the responses in initial third of the ratio were punished. Disruption of responses before the punished segment of the ratio was a conspicuous feature of the performances when the middle or final third of the ratio was punished. Two of the punishment conditions produced similar effects on both fixed-ratio baselines but punishing the final third of the ratio suppressed the punished responses of the ratio only with the fixed-ratio 99 schedule. General effects of all punishment conditions included consistent intra-session recoveries of partially suppressed performances, the rapid recovery of the FR performances after the punishment dependency was removed after complete suppression, and the facilitation of overall and/or local response rates of most subjects by low-intensity shock.