Summation: Assessment of a configural theory

Abstract

In five experiments, rats were given Pavlovian pairings of auditory and visual stimuli with delivery of food pellets. Experiment 1 found greater responding to an AB compound after training with the individual A and B stimuli, compared with responding both to the A and B elements and to a separately trained CD compound. Experiment 2 found this enhanced responding to depend on the associative strengths of A and B. In Experiment 3, responding was greater to a CD compound than to the other compounds after an AB-, AD+, BC+ training procedure. In Experiment 4, responding to an AB compound was greater than that to the elements after A was reinforced on a 100% schedule and B on a 50% schedule. In Experiment 5, responding to an ACcompound was greater than that to either A or C after an AB+ , CD+ , A-training procedure. A configural theory, such as that proposed by Pearce (1987), anticipates sununation in none of these procedures, unless the conditioned context is assumed to have a salience greater than zero. In order to predict summation in Experiments 3, 4, and 5, a context salience greater than that of the elements must be assumed. However, such an assumption also anticipates that extinction of a 100% stimulus should eliminate responding to a 500A! stimulus. The results of Experiment 3 contradicted that prediction. These results conform better to the expectations of elemental models of conditioning.A problem ofcontinuing interest in associative learning is that of specifying the behavior to a compound stimulus, AB, in terms of the behavior to its components, A and B. One can identify two broad classes oftheories that attempt to deal with this problem.What has sometimes been call the "elemental" approach focuses on the compound as composed of its constituent elements. According to this approach, the compound stimulus consists primarily of its component parts and the associative strength ofthe compound is derived by some rule for summing the associative strengths of those components. This historically popular view has been incorporated into many theories oflearning (e.g., Hull, 1943;.A less popular, but attractive, approach has been called the "configural" approach. This approach views each compound as a new stimulus, distinct from its elements. Responding to that compound then depends on its receiving generalization based on its similarity to the trained elements. Although historical versions ofthis approach have sometimes left that similarity poorly defined, a recently proposed configural theory specifies the element/compound relation in terms of an explicit generalization rule linking them (Pearce, 1987(Pearce, , 1994.Each of these approaches has its attractions. The elemental approach offers a simple, analytic basis for building up a compound from its component parts. It can provide a natural account of many phenomena that result from compound presentation, such as summation, blocking, and over-

An attention-modulated associative network

“…There are numerous demonstrations that animals respond to the compound of two CSs more than to each individual CS (e.g., Kehoe, 1982Kehoe, , 1986Rescorla, 1997), consistent with the assumption that the associative strength of the compound equals the sum of the strengths of the two CSs. However, there are also numerous reported failures to observe summation in Pavlovian conditioning paradigms.…”

“…That is, although the stimuli did not overlap spatially, their proximity may still have effected some normalization within the pigeons' visual systems. Indeed, these stimuli may have affected one another's detectability at a more peripheral level if, by looking at one stimulus, the pigeons' gaze was directed away from other concurrently presented of CSs from the same modality do not produce more responding than do the individual CSs themselves, this could explain the many failures to observe summation in autoshaping with pigeons (Aydin & Pearce, 1995, 1997Rescorla & Coldwell, 1995), because the CSs used in those experiments were from the same (visual) modality. In light of this, Wagner (2003) has specified operations in the replaced elements model that capture this relation (see also Myers et al, 2001).…”

“…However, there are also numerous reported failures to observe summation in Pavlovian conditioning paradigms. Most of these failures have occurred in autoshaping experiments with pigeons (e.g., Aydin & Pearce, 1995, 1997Rescorla & Coldwell, 1995). Nonetheless, both successes and failures to observe summation have been reported in other paradigms, such as the conditioned nictitating membrane response in rabbits (Kehoe, Horne, Horne, & Macrae, 1994) and the conditioned magazine approach with rats (Pearce, George, & Aydin, 2002;Rescorla, 1997;Thein, Westbrook, & Harris, 2008).…”

Summation of reinforcement rates when conditioned stimuli are presented in compound.

“…There are numerous experiments showing that responding to a compound is greater than responding to the individual CSs that make up the compound (e.g., Kehoe, 1982;Kehoe, 1986;Rescorla, 1997;Thein, Westbrook, & Harris, 2008), consistent with the principle of summation.…”

Effects of pretraining on acquisition of novel configural discriminations in human predictive learning

“…For example, Pearce's configural theory (Pearce, 1987(Pearce, , 1994 is better than the Rescorla-Wagner model (Rescorla & Wagner, 1972) in accounting for resistance to interference ( , ; , , y , , (Pearce & Wilson, 1991;Shanks, Charles, Darby, & Azmi, 1998;Williams, Gawel, Reimer, & Mehta, 2005) and for salience effects in disd crimination learning (Pearce & Redhead, 1993;Redhead & Pearce, 1995), whereas the Rescorla-Wagner model is better able to account for summation (Myers, Vogel, Shin, & Wagner, 2001;Rescorla, 1997Rescorla, , 1999Wagner, 2003) and relative validity (Wagner, Logan, Haberlandt, t & Price, 1968). Thus, there is growing acceptance that r the extent to which stimuli are processed configurally or elementally is flexible, rather than representing mutually exclusive alternatives.…”