A further application of the active time model to multiple concurrent variable-interval schedules

Abstract

In this experiment we show that the active time model (ATM) accurately predicts probe data from multiple concurrent VI VI schedules. Subjects were trained under a concurrent VI 30-s VI 60-s and a concurrent VI 60-s VI 120-s schedule. Two types of unreinforced probes were then conducted. The first paired the two VI 60-s stimuli. These stimuli, while equivalent in their associated absolute rates of reinforcement, differed in their relative rates of reinforcement. The second probe paired the VI 30-s stimulus with the relatively rich VI 60-s stimulus. In contrast with the first probe, these stimuli differed in their absolute rates of reinforcement, while being similar in their relative rates. During the first set of probes, birds preferred the VI 60-s stimulus trained with the VI 120-s schedule. During the second set of probes, birds were indifferent to the two stimuli. These results are less extreme than others reported in the literature. Nonetheless, we found that ATM accurately fit individual subject data in both sets of probes. In contrast a variant of scalar expectancy theory did not fit the data at either the individual or group level.

Preference as a Function of Active Interresponse Times: A Test of the Active Time Model

“…If the switching functions shown in Figure 2 are associated with discriminative stimuli, then Belke's probes essentially pair a “rich” switch function with one that is “lean.” Such a pairing would cause a subject to switch more often from the VI 40 20 stimulus than from the VI 40 80 stimulus. McKenzie and Cleaveland (2010) tested this hypothesis in a procedure similar to Belke's, and found that the observed switch functions could be used to accurately model the individual preferences obtained during probes. The following experiment extends the work of McKenzie and Cleaveland by noting that the functions in Figure 2 make a novel prediction.…”

“…This time variable has been termed “active time,” and the model describing its relevance to choice behavior has been designated the active time model, or ATM (Cleaveland, 1999). ATM is a stochastic, molecular model that successfully describes a range of choice behavior for pigeons responding on concurrent VI VI schedules of reinforcement (Brown & Cleaveland, 2009; Cleaveland 1999, 2008; McKenzie & Cleaveland, 2010). The model assumes that during training pigeons learn a function that relates active times to switches and stays into and out of choice “states.” With its emphasis on interresponse times and switches versus stays, ATM falls within a broad theoretical approach to choice behavior that is shared by models such as momentary maximization (Shimp, 1969) and the stay/switch model (MacDonall, 2009).…”

“…This time variable has been termed ''active time,'' and the model describing its relevance to choice behavior has been designated the active time model, or ATM (Cleaveland, 1999). ATM is a stochastic, molecular model that successfully describes a range of choice behavior for pigeons responding on concurrent VI VI schedules of reinforcement (Brown & Cleaveland, 2009;Cleaveland 1999Cleaveland , 2008McKenzie & Cleaveland, 2010). The model assumes that during training pigeons learn a function that relates active times to switches and stays into and out of choice ''states.''…”

The active time model of concurrent choice

“…ATM’s core assumption is that active time is a primary controlling variable of concurrent VI VI choice. In support of this assumption, Figs 3 and 4 provide active time functions drawn from discrete-trial, free-operant and multiple concurrent procedures [ 24 , 27 , 29 ]. Fig 3 provides functions drawn from the relatively rich VI of a pair, while Fig 4 provides functions drawn from the relatively lean VI.…”

“…B) Functions for three subjects trained first in a VI 60-s VI 180-s schedule and then in a VI 20-s VI 60-s schedule [ 24 ]. The time bins are in 5-s intervals up to 4 s. C) Functions for three birds trained with multiple concurrent, free-operant VI VI schedules and a Findley procedure [ 29 ]. The schedules utilized were a VI 30-s VI 60-s and a VI 60-s VI 120-s, and the time bins are in 25-s intervals up to 4 s.…”