Exteroceptive Control of Fixed‐interval Responding

Abstract

Two pigeons were exposed to several fixed-interval schedules of food reinforcement. In some cases, exteroceptive stimuli associated with the passage of time were present. Such visual "clock" stimuli were found to gain almost complete control over the behavior, although at the longest fixed interval studied, the superposition of a new temporal discrimination upon the visual discrimination was observed. Where clock stimuli were made contingent upon the birds' behavior, a new form of responding was generated. This behavior was discussed in terms of positive and negative response-tendencies resulting from several stimulus factors: Some of these functioned as S(Delta)'s and secondary negative reinforcers; some functioned as S(D)'s and secondary positive reinforcers; and some were ambiguous with respect to reinforcement conditions. A "pure temporal" discrimination was superimposed upon these factors, but its exact nature was indeterminate from the present data.

Escape From Serial Stimuli Leading to Food

“…Under an FI schedule, time since reinforcement apparently serves a discriminative function similar to that of the colors displayed on our key; when exteroceptive stimuli are added to such a schedule, as in Ferster and Skinner's (1957) "added clock," the pause at the beginning of the interval is lengthened (see also Segal, 1962). Similarly, when brief exteroceptive stimuli are regularly substituted for some deliveries of the reinforcer, pauses develop following each presentation of the brief stimulus (Gollub, 1977).…”

“…In terms of their locus in time, some stimuli might be said to be more negative than others. (For similar relationships, in which the rate of responding seems to depend on the temporal distance between the stimulus and the reinforcer rather than on the receipt or nonreceipt of the reinforcer, see Dews, 1962Dews, , 1966Farmer & Schoenfeld, 1966;Segal, 1962. ) However, this characterization is already stretching the definition of negative discriminative stimulus, both historically and as used in other contexts.…”

Signaled reinforcement effects on fixed-interval performance of the rat

“…Rats in the yoked group received the signal when their paired master rats received the signal and the reinforcement. This procedure, however, might have introduced some artifacts because a stimulus in the interval affects the rate and pattern ofFI responding (e.g., Eckerman & McGourty, 1969;Farmer & Schoenfeld, 1966a, 1966bFerster & Skinner, 1957;Kendall, 1972;Segal, 1962). Thus, we used as an appropriate control the unsignaled group instead of the yoked one.…”

PERIODIC SHOCK WITH ADDED CLOCK1

“…In addition, the present results include a quantitative expression of the degree of curvature and details of temporal changes in response rate at two intensities of shock. The study by Segal (1962) of the effect of a clock added "to a fixed-interval reinforcement was procedurally similar to the present experiment. In Segal's experiment, the successive quarters of Fl schedules were identified by different cues (clock cues).…”

“…The addition of a sequence of cues temporally related to the occurrence of reinforcement accentuates the positive acceleration, whether the cues change continuously (Ferster and Skinner, 1957, p. 266 ff; cf, e.g., Fig. 311, p. 268) or discretely (Segal, 1962;Weiss and Laties, 1964). The procedure of adding a sequence of cues temporally related to reinforcement has been called "added clock" (Ferster and Skinner, 1957), and the cues themselves have been called "clock cues" (Hendry and Dillow, 1966).…”