Operant Conditioning – Chapter 9 Theories of Learning October 19, 2005 Class #25

Lecture Outline I. Shuttle Box Experiment II. Avoidance paradox III. Two-process Theory of Avoidance

Solomon and Waynne (1953) and the Shuttle Box Experiment

The Shuttle Box Experiment Shuttle box consists of: 2 chambers separated by a barrier several inches high Could freely move between chambers Separate lights Metal floor that could be electrified to deliver shock Experimental Session – 10 trials each Dog placed in one compartment of a shuttle box After a time, light in the compartment that dog was in went off, while other light stayed on 10 seconds later, the dog received a shock through the floor until jumped over barrier Measured response latency (how long it took dog to jump over barrier once light went out) What they found: Escape first: First few responses were usually longer than 10 seconds. So dog was getting shocked and then escaping Avoidance response: By roughly the 5 th trial, dogs response latency was less than 10 seconds. So dog never received shock in these cases.

Avoidance Paradox Sidman (1989) “Successful avoidance meant that something – the shock – did not happen, but how could something that did not happen be a reinforcer?” Sidman goes on to say that things are not happening all the time and seems illogical to say that things that did not happen explain things that did Escape makes sense because stimulus present Avoidance involves no change in shock condition No shock pre- and post- behavior

Two-Process Theory There is no paradox: No such thing as avoidance, just escape. In both cases, fear is being escaped Two kinds of learning involved with avoidance: Pavlovian and operant Dog learns to jump hurdle to escape the shock – Jumping is negatively reinforcing What reinforces jumping when there is no shock to escape? Classical conditioning: Shock (US) ---- Fear (UR) Extinguished Light (CS) ---- Fear (CR) Removal of fear evoking CS is observable change in the stimulus environment that acts as negative reinforcer

Miller (1948) Escape from an aversive stimulus can reinforce behavior Through association with shock, the white compartment had become a CS for fear, and escaping from it was reinforcing First part: Rats in white chamber shocked Chamber had door that rat could jump through to get to black chamber where no shock Put rats back in white chamber and did not shock them; Rats continued to go to black chamber Second part: Miller then put rats into white compartment and closed door Rats could open door by running on a wheel Rats soon learned to run on wheel to open door, even though no shocks presented

Discriminated or Signalled Avoidance A warning stimulus signals a forthcoming S Aversive If the required response is made during the warning stimulus, before the S Aversive occurs, the subject avoids the shock If a response is not made during the warning stimulus, the S Aversive occurs, and terminates when the required response is made

The Two-Process Theory of Avoidance Mowrer (1947, 1960) Explains avoidance learning in terms of two necessary processes: 1. The subject learns to associate the warning stimulus with the S Aversive 2. The subject can then be negatively reinforced during the warning stimulus

Problems with Two-Factor Theory Avoidance with no sign of fear Problem: Fear should be greatest when avoidance responses the strongest Signs of fear may include heart rate increase, changes in breathing, sweating If theory correct, should be able to observe 1.) Increase in fear when signal for shock presented 2.) Decrease in fear once avoidance response made Evidence that observable signs of fears begin to disappear as subjects become more experienced with the task Example: Soloman and Wynne (1953) noted that dogs initially show signs of fear (urination) when light turned off These signs disappeared once they making frequent avoidance response

Problems with Two-Factor Theory Failure of avoidance behaviors to extinguish Two-Factor model uses classical conditioning. From a Pavlovian perspective, each trial that shock is avoided is a extinction trial Extinction: CR gets weaker and disappears the more that CS not paired with US Avoidance consists of presentation of CS without US Example: CS (Darkness) without US (Shock)

Problems with Two-Factor Theory Two-Factor model: Predicts that avoidance responding should eventually deteriorate after series of trial without shock. We would expect cycles of conditioning. Problem: Avoidance behavior is extremely resistant to extinction

Anxiety Conservation Hypothesis Solomon & Wynne (1954) Proposed a modification of two-process theory to account for why extinction does not occur In avoidance conditioning: The organism avoids the stimulus so quickly that there is very little exposure to the CS, so extinction does not occur, and in fact, incubation may occur (an increase in fear due to the brief exposure to the fear-eliciting CS)

Avoidance Conditioning and Phobias Phobia: A strong, persistent, and unwarranted fear of some specific object or situation

Avoidance Conditioning and Phobias Phobias are thought to be a classically conditioned response Extinction doesn’t ever seem to occur… Why???

Lab experiments compared to real world… Mineka (1985) Illustrates some differences: In the lab the animal avoids the UCS (the shock) In human phobic conditioning the person avoids the CS (the dog – not the attack)

But… Stampfl (1987) Fear response in phobias is often established whith only one brief pairing of Cs/UCS The organism must therefore avoid both CS and UCS The organism will then likely show successful avoidance on 100% of these trials

Credits: