Avoidance behavior: Why don’t we know more than we do and why aren’t we working on it?
Ron Allen and Jeff Kupfer
Simmons University and University of Colorado Denver
There are two general procedures of negative reinforcement; escape and avoidance. In escape the procedure and effects are exceedingly clear; in the presence of aversive stimulation a response terminates (or reduces) the aversive stimulus. When the response is increased in probability under similar antecedent conditions we term the effect negative reinforcement. In avoidance, the procedures and effects are clear, but the theoretical and conceptual connections between the two can be less so. In the absence of identified aversive stimulation a response delays or cancels an impending aversive event. If the response is increased in probability under similar antecedent conditions we term the effect negative reinforcement, but we might not be able to identify an immediate consequence of the response. In lay terms we might speak teleologically and say the organism is responding in order to avoid a future event. Are we suggesting that a nonevent is reinforcing the event? Where is the moment of reinforcement?
In 1969 Richard Herrnstein published an article in the Psychological Review entitled Method and Theory in the Study of Avoidance. In his article Herrnstein detailed to date the evolution of procedures to study avoidance and the accompanying conceptualizations concerning the nature of avoidance behavior. Perhaps the earliest publication of procedures we might term avoidance was provided by Bekhterev (1913). Under the Bekhterev procedure, harnessed dogs stood with one paw on a metal plate through which an electric shock could be delivered. Across trials, the presentation of shock was preceded by a neutral stimulus. Naturally, the electric shock elicited flexion in the dog’s leg on the plate, possibly interrupting contact with the shock. Within a few trials, the dog’s leg flexed during the neutral stimulus (or warning stimulus) and the presentation of electric shock was coincidently avoided.
Given the period in history of the experiment, as well as the structure of Bekhterev’s procedures, the leg flexion during the warning stimulus was characterized as a conditioned response (CR) elicited by the warning stimulus, now being a conditioned stimulus (CS) having acquired eliciting properties through pairing with the electric shock (unconditioned stimulus (US). This interpretation raised little conceptual concerns as the elicited response had a clear antecedent and little consideration was given to the consequences of the leg flexion.
In the ensuing decades, the role of the consequence of a response in the context of such experimentation rose in eminence (e.g., Hull, 1934). Brogden, Lipman, and Culler (1938) reported that rats responding during the warning stimulus (or CS) that canceled an impending shock increased and were sustained in greater probability than responding during the warning stimulus that had no effect on subsequent shock. Thus, in short time, operant accounts of avoidance responding became the dominant conceptualization.
The procedure described above became termed Discrete Trial, Discriminated Avoidance, or Signaled Avoidance. The problem of the reinforcement of the avoidance response by a future nonevent was seemingly answered by the emergence of the Two-Factor Theory of Avoidance. Mowrer (1947) suggested that the temporal contiguity between the neutral stimulus and shock would result in the elicitation of fear (or aversiveness suggested by Schoenfeld in 1950) by the CS. A designated response would terminate the conditioned stimulus (and the conditioned fear) and coincidentally omitted the impending shock. Thus, what had been conceptualized as avoidance responding could now be seen molecularly as escape (with a clear moment of reinforcement). The two factors in the theory were (1) respondent conditioning in the creation of the conditioned aversive stimulus and (2) operant conditioning in the negative reinforcement of responding escaping the conditioned stimulus. Forms of the Two Factor Theory remain contemporary in behavior analysis; control of responding in signaled avoidance remains the experimental analog of the CMO-R (e.g., Michael, 2007) and the concept of experiential avoidance is prominent in conceptual analyses of anxiety and other emotions (e.g., Friman et al. (1998). Interestingly, Herrnstein (1969) conceptualized the warning stimulus as a discriminative stimulus. Michael argues against the discriminative stimulus interpretation as the converse condition-responding in the absence of the warning stimulus not producing the termination of the warning stimulus does not exist.
However, additional laboratory results have proven challenging for the Two Factor Theory. In 1953, Sidman demonstrated the acquisition and maintenance of avoidance responding by rats without an exteroceptive warning stimulus (now termed Free Operant or Sidman Avoidance). Under these procedures brief electric shocks were presented under two available schedules, the shock-shock (s-s) interval and the response-shock (r-s) interval schedule. In the absence of responding shocks were presented periodically under the s-s schedule (e.g., every 5-s). The occurrence of a response initiated the r-s schedule (e.g., 10-s) and, barring any additional response, shock was presented at the end of that interval, and the s-s schedule was again in effect. Ongoing responding with inter-response times shorter than the r-s interval could result in the avoidance of all shocks (but, interestingly this rarely occurred, but responding was nevertheless maintained). But, where was the aversive stimulus from which to escape? Could responding be maintained solely by the resultant nonoccurrence of an event (or a moment of reinforcement)?
Herrnstein (1969) noted that some investigators (e.g., Anger, 1963) postulated that unmeasured stimuli such as those associated with the passage of time from the last shock or response could take on aversive properties. Escape from such conditioned aversive temporal stimuli could sustain the applicability of the two-factor theory. The development of such conditioned aversive temporal stimuli was suggested to be made possible by the regularity of the s-s and r-s intervals under the Sidman avoidance (or Free Operant Avoidance) procedure.
In 1966, Herrnstein and Hineline introduced avoidance procedures challenging the necessity of conditioned aversive temporal stimuli in accounting for the maintenance of responding. Under these procedures, brief electric shock could be delivered noncontingently and randomly under two schedules, a high-probability and a low-probability distribution. The high-probability schedule was in effect at the start of each session and after any delivered shock. The low-probability schedule was in effect following any response until the next shock was delivered. Responding by rats was acquired and maintained under this arrangement. Additionally, rates of responding were demonstrated to be functionally related to alterations to the differences in rates of shock between the two shock schedules. The use of random schedules of shock delivery would seemingly forego the formation of conditioned aversive temporal stimuli, and thus challenge two-factor theory. How then to account for responding? Herrnstein and Hineline suggested that the best account of responding was that it resulted in shock frequency reduction. Sidman (1962) had similarly suggested shock frequency reduction as responsible for avoidance responding. The question for molecular theorists remains can behavior be related to contingent changes in rates of events (rather than temporal contiguity with consequential stimuli or a moment of reinforcement)? For molar theorists (e.g., Baum. 1995) the answer is a clear affirmative. Herrnstein and students have demonstrated numerous forms of the Matching Law (e.g., Baum, 1974; Herrnstein, 1961) demonstrating the relations between relative rates of responding and relative rates of reinforcement. The demonstration of functional relations between responding and reductions in the rates of aversive events would seem to be additional support for molar theories of reinforcement. However, the molecular vs. molar accounts debate concerning behavior control continue and may be a future topic of blog discussions.
Finally, we could ask the question “given the aversive events and trauma humans experience, shouldn’t the experimental analysis of behavior have a robust research program allowing us to act to reduce and blunt the effects of trauma?”
References
Baum, W. M. (1995). Introduction to molar behavior analysis. Mexican Journal of Behavior Analysis, 21, 7–25.
Bekhterev, V. M. (1913) Objective psychologic. Leipzig & Berlin: Teubner
Brogden, W. J., Lipman, E. A., & Culler, E. (1938). The role of incentive in conditioning and extinction. American Journal of Psychology, 1938, 51, 109-117.
Friman, P.C., Hayes, S.C., and Wilson, K.G.(1998) Why behavior analyst should study emotions: The example of anxiety. Journal of Applied Behavior Analysis, 31, 137-156.
Herrnstein, R.J. (1969). Method and theory in the study of avoidance. Psychological Review, 76 (1), pp.49-69.
Herrnstein, R. J., & Hineline, P. N. Negative reinforcement as shock-frequency reduction. Journal of the Experimental Analysis of Behavior, 1966, 9, pp. 421-430.
Hull, C. L. Learning: II. The factor of the conditioned reflex. (1934) In C. Murchison (Ed.), A handbook of general experimental psychology. Worcester: Clark University Press.
Michael, J. Motivating Operations. (2007). In J. O. Cooper, T. E. Heron, & W. L. Heward (Eds.), Applied behavior analysis (pp. 374-391). Upper Saddle River, NJ: Prentice Hall/Merrill
Mowrer, O. H. On the dual nature of learning—A re-interpretation of “conditioning” and “problem solving.” (1947) Harvard Educational Review, 17, 102-148.
Schoenfeld, W. N. An experimental approach to anxiety, escape and avoidance Behavior. (1950) In P. H. Hoch & J. Zubin (Eds.), Anxiety. New York: Grune & Stratton. (Republished: New York, Hafner, 1964.)
Sidman, M, Avoidance conditioning with brief shock and no exteroceptive warning signal. (1953). Science, 118, 157-158.
Sidman, M. Reduction of shock frequency as reinforcement for avoidance behavior. (1962). Journal of the Experimental Analysis of Behavior, 15, 247-257.