From Reflexes to Learned Responses: Decoding Classical Conditioning

Classical Conditioning Exercises This week’s readings and exercises focus on classical (Pavlovian) conditioning. Pavlovian conditioning is the fundamental building block of learning; it is central to how organisms adapt to their environment. Classical conditioning occurs in all animals. Single-celled creatures, such as paramecia, are capable of Pavlovian conditioning, and classical conditioning is operating in many behaviors exhibited by humans. Classical conditioning is founded on the relationship between in-born reflexes called unconditioned responses and the unconditioned stimuli that produce those reflexes. The term unconditioned is instructive; unconditioned implies no learning required. The relationship between the unconditioned stimulus (US) and the unconditioned response (UR) exists the first time the unconditioned stimulus is presented. Furthermore, each time the US is presented, the UR reliably follows. In contrast, a conditioned stimulus requires learning (conditioning) before it will elicit a conditioned (learned) response. Many inborn reflexes have importance to an organism because of their survival value. Some examples are eye blinks that occur in response to something directed to the eye, or salivation in response to food in one’s mouth. You may ask what is the survival utility of these responses? Well, if one did not blink, one could suffer an injury to the eye, and without saliva present, it is difficult to swallow one’s food, and saliva contains enzymes that begin digestive processes. To reiterate, unconditioned stimuli are stimuli that produce unconditioned responses. In the instances noted above the unconditioned stimuli are projectiles toward the ey e and food in the mouth. A projectile approaching your eye (an unconditioned stimulus) causes a reflexive blink (unconditioned response), you don’t have to learn to blink to avoid something approaching your eye. When food (unconditioned stimulus) is placed in one’s mouth you salivate automatically (unconditioned response). The following terms are must be mastered, in order to understand classical conditioning principles. Unconditioned stimulus (US) - a stimulus that elicits a predictable response without learning, for example, an air puff to your eye will cause you to blink. The air puff is the US and the blink is the UR. Unconditional response (UR) - the automatic, unlearned response to an unconditioned stimulus (US). For example, salivating is an unconditioned response to food in one’s mouth. Food is the US (unconditioned stimulus) and salivation is the UR (unconditioned response). Conditioned stimulus (CS) – the critical feature of a conditioned stimulus is that learning (conditioning) must occur before it can elicit a response. Prior to conditioning a CS is a neutral stimulus to an organism. By neutral stimulus it is meant that it has no capacity to produce an unconditioned response. After pairing a conditioned stimulus with an unconditioned stimulus, however, a conditioned stimulus comes to have the properties of the unconditioned stimulus in that it can elicit a response, a conditioned response. For example, the tone of a bell is neutral with regard to salivating. A bell ring doesn’t produce salivation. However, if we were to ring a bell prior to placing food in your mouth several times, the tone of the bell will acquire the capacity to elicit salivation. The bell, which had been a neutral stimulus, is now a conditioned stimulus (CS); it now elicits salivation, a conditioned response. Conditioned response (CR) – a response to a conditioned stimulus. In the example above, the conditioned response (CR) is the salivation to the bell (CS).