Following a shaping procedure, pigeons' pecks were maintained on concurrent, independent variable-interval schedules in which peeks on either of two keys produced different durations of shock-free time. Shock-free times scheduled as a consequence of peeking the two keys were at different times, 3 min, 1 min, or 10 sec. The relative rates of peeking a key increased as the relative duration of shock-free time for that key increased. Results are consistent with the view that the effects of negative reinforcement are parallel, but opposite in sign, to positive reinforcement and that shock-free time is analogous to food duration in positive reinforcement experiments.Baum (l973b), Fantino (1973), and others have recently outlined many similarities between the variables controlling behavior in negative reinforcement procedures with those controlling behavior in positive reinforcement procedures. For example, simple schedules of negative reinforcement maintain patterns of behavior similar to the pattern maintained by the same schedule of positive reinforcement (Azrin, Holz, Hake, & Ayllon, 1963; Dinsmoor, 1962). Shock density seems to be a fundamental variable in determining the aversive ness of a situation, just as food density seems to be a basic determinant of food-reinforced responding (Auto!, 1969;Herrnstein & Hineline, 1966; Sid!nan, 1962). Furthermore, the frequency of shock·free times bears the same quantitative relationship to response rates in negative reinforcement procedures that frequency of food presentation bears in positive reinforcement procedures (deVilliers, 1972;Herrnstein, 1970). The same has been found with time allocation measures of negative reinforcement in concurrent schedules (Baum, 1973b).The duration of a positively reinforcing event has systematic effects upon behavior. Because the duration of reinforcing grain presentations has not been found to have a Significant influence upon response rate in singlekey situations with pigeons (Catania, 1963), a more sensitive measure, the relative rate of responding on concurrent variable-interval schedules, has generally been employed. In this procedure, "matching" is said to occur if the relative time or relative number of responses on one key is equal, or nearly equal, to the duration of reinforcers delivered on that key. Studies that have employed the concurrent choice procedure have consistently found that the relative response rate is pre- dicted by a comparison of the respective relative reinforcement durations, although it is clear that duration of positive reinforcement is a less potent determinant of preference than relative frequency (Brownstein, 1971;Schneider, 1973;Todorov, 1973). In other words, qualitative preferences for longer durations have been found, but matching has not beenlound.A concurrent schedule of food presentation identifies preferences that are not revealed by response rates on simple schedules. If positive and negative reinforcement can be subsumed under the same conceptual framework (Baum, 1973), we might expect a simil...

By responding on a changeover key, subjects could change the prevailing unsignalled VI 65-sec. schedule to a signalled, but otherwise identical, schedule. On the signalled schedule a brief tone preceded reinforcement. Regardless of the duration of the signal (5.0, 3.0, 1.0, 0.5, or 0.1 sec.), subjects strongly preferred the signalled schedule. Withdrawal of the signal produced a rapid decline in the changeover key response rate, demonstrating that production of the signalled condition maintained the responding. Results support the information hypothesis.