Extinction under a behavioral microscope: Isolating the sources of decline in operant response rate

Abstract

Extinction performance is often used to assess underlying psychological processes without the interference of reinforcement. For example, in the extinction/reinstatement paradigm, motivation to seek drug is assessed by measuring responding elicited by drug-associated cues without drug reinforcement. Nonetheless, extinction performance is governed by several psychological processes that involve motivation, memory, learning, and motoric functions. These processes are confounded when overall response rate is used to measure performance. Based on evidence that operant responding occurs in bouts, this paper proposes an analytic procedure that separates extinction performance into several behavioral components: 1) the baseline bout initiation rate, within-bout response rate, and bout length at the onset of extinction; 2) their rates of decay during extinction; 3) the time between extinction onset and the decline of responding; 4) the asymptotic response rate at the end of extinction; 5) the refractory period after each response. Data that illustrate the goodness of fit of this analytic model are presented. This paper also describes procedures to 1) isolate behavioral components contributing to extinction performance; 2) make inferences about experimental effects on these components. This microscopic behavioral analysis allows the mapping of different psychological processes to distinct behavioral components implicated in extinction performance, which may further our understanding of the psychological effects of neurobiological treatments.

Interval timing under a behavioral microscope: Dissociating motivational and timing processes in fixed-interval performance

“…This characterization is consistent with those of IRTs in nontiming paradigms, such as the variable-interval (VI) schedule of reinforcement (Brackney et al 2011;Cheung et al, 2012;Conover, Fulton, & Shizgal, 2001;Shull 2004;Shull et al, 2001;Shull et al, 2002). Also, mean IRTs in FI 30-s trials and in the last 30 s of FI 90-s trials were remarkably similar, suggesting that IRTs are sensitive to the expected time of food.…”

“…Selected estimates and derived statistics were also rescaled as proportions of the FI. Parameter estimates and derived statistics, whether rescaled or not, were log transformed or, in the case of mixture weights, log-odds transformed for statistical analysis (Cheung et al, 2012). A two-tailed Grubbs' test was performed on log-transformed estimates before each statistical analysis, to detect potential outliers, because the MLE method sometimes yields extreme estimates when applied to mixture-distribution models (Cheung et al, 2012).…”

“…Parameter estimates and derived statistics, whether rescaled or not, were log transformed or, in the case of mixture weights, log-odds transformed for statistical analysis (Cheung et al, 2012). A two-tailed Grubbs' test was performed on log-transformed estimates before each statistical analysis, to detect potential outliers, because the MLE method sometimes yields extreme estimates when applied to mixture-distribution models (Cheung et al, 2012). Outlier data were removed when they were detected with significance criterion α = .05; in most instances, outliers were detected with α = .01 and removal of the outlier did not change the outcome of significance tests.…”

“…More specifically, these data suggest that, at the beginning of each trial, subjects enter either a timing state, emitting target responses generated by a timing mechanism, or they enter a nontiming state, emitting target responses randomly. Alternation between these two states may reflect a more general fluctuation in behavioral control by operant schedules (Brackney, Cheung, Neisewander, & Sanabria, 2011;Cheung, Neisewander, & Sanabria, 2012;Shull, 2004;Shull, Grimes, & Bennet, 2004;Shull, Gaynor, & Grimes, 2001, 2002Gibbon, 1995;Myerson & Miezen, 1980). Performance in FI schedules is thus likely an expression of cycling into and out of multiple behavioral states until reinforcement is obtained.…”

“…Using strategies formulated by Killeen, Hall, Reilly, and Kettle (2002), this study pursued these goals by conducting a microstructural analysis of performance (Cheung et al, 2012) in two FI schedules and two levels of food deprivation. Figure 1 shows a schematic of how behavior is organized in an FI trial.…”