Quantitative analyses of observing and attending

Abstract

We review recent experiments examining whether simple models of the allocation and persistence of operant behavior are applicable to attending. In one series of experiments, observing responses of pigeons were used as an analog of attending. Maintenance of observing is often attributed to the conditioned reinforcing effects of a food-correlated stimulus (i.e., S+), so these experiments also may inform our understanding of conditioned reinforcement. Rates and allocations of observing were governed by rates of food or S+ delivery in a manner consistent with the matching law. Resistance to change of observing was well described by behavioral momentum theory only when rates of primary reinforcement in the context were considered. Rate and value of S+ deliveries did not affect resistance to change. Thus, persistence of attending to stimuli appears to be governed by primary reinforcement rates in the training context rather than conditioned reinforcing effects of the stimuli. An additional implication of these findings is that conditioned “reinforcers” may affect response rates through some mechanism other than response-strengthening. In a second series of experiments, we examined the applicability of the matching law to the allocation of attending to the elements of compound stimuli in a divided-attention task. The generalized matching law described performance well, and sensitivity to relative reinforcement varied with sample duration. The bias and sensitivity terms of the generalized matching law may provide measures of stimulus-driven and goal-driven control of divided attention. Further application of theories of operant behavior to performance on attention tasks may provide insights into what is referred to variously as endogenous, top-down, or goal-directed control of attention.

Introduction

Problems in the allocation and persistence of attention are involved in many psychological disorders. For example, attention is too easily disrupted in those with attention-deficit/hyperactivity disorder (ADHD; American Psychiatric Association, 1994). In addition, persistent misallocation of attention has been identified in people with schizophrenia (Nestor and O’Donnell, 1998), and as been implicated in educational difficulties with the developmentally disabled (i.e., stimulus overselectivity; Dube and McIlvane, 1997, Lovaas et al., 1979). Finally, persistent and problematic attentional biases to drug cues have been noted with drug abusers (e.g., Ehrman et al., 2002, Johnsen et al., 1994, Lubman et al., 2000, Townshend and Duka, 2001).

Attention is widely recognized to be governed in part by both stimulus features and the goals of the organism (see Yantis, 2000, for review). In addition, the deployment of attention is considered to be a skill modifiable by experience (e.g., Gopher, 1992). Thus, an understanding of the impact of reinforcement variables on the allocation and persistence of attention may help to suggest improved behavioral interventions for the psychological disorders noted above. Recently, we have been examining the applicability of quantitative models of operant behavior like the matching law and behavioral momentum theory to the allocation and persistence of attending. In one series of experiments (Section 2 below), we used observing responses of pigeons as an analog of attending. Observing responses bring sensory receptors into contact with stimuli to be discriminated and have long been considered an analog of attending (Wyckoff, 1952). In the typical procedure used to study observing responses, periods in which food is available for a response on some schedule of reinforcement alternate with periods in which the response is not reinforced and food is never available (i.e., extinction). During each session, these alternating periods of food availability versus extinction are not signaled. Observing responses (e.g., pecks on a second key) produce brief discriminative stimuli signaling whether food is available (i.e., S+) or not (i.e., S−). Below we review experiments examining the applicability of the matching law (Section 2.1) and behavioral momentum theory (Section 2.2) to observing behavior. Observing behavior is generally believed to be maintained by the conditioned reinforcing properties of S+ presentations, thus along the way we will examine the implications of these experiments for an understanding of conditioned reinforcement in general.

In a second series of experiments (Section 3 below), we examined the applicability of the generalized matching law to the allocation of attention in a divided-attention task. In this task, pigeons are presented with compound samples comprised of a combination of two elements (i.e., a color and a line orientation) and single-element comparison stimuli (i.e., two colors or two line orientations) in a delayed-matching-to-sample procedure. Accurate performance requires attending to both elements of the compound stimuli. We apply the generalized matching law to changes in performance associated with variations in the relative rates of reinforcement for attending to the elements of the compound samples.