Chapter 5: Learning and Behavior Learning How Learning is Studied Ivan Pavlov Edward Thorndike eliciting stimulus emitted

Transcription

1 Chapter 5: Learning and Behavior A. Learning-long lasting changes in the environmental guidance of behavior as a result of experience B. Learning emphasizes the fact that individual environments also play a role which may go against the concept of survival of the fittest C. Three Assumptions that psychologists make in their study of behavior 1. Behavior is law 2. Behavior is controllable 3. Control of behavior is desirable I. How Learning is Studied A. Both Ivan Pavlov and Edward Thorndike began the process of studying learning in the lab B. Pavlov s Procedure 1. Both Pavlov and Thorndike evoked an eliciting stimulus a stimulus that evokes behavior, commonly as a result of natural selection 2. Pavlov would strap a dog to a harness and present food to it to the ticking sound of a metronome 3. After several times the animal began to salivate and look toward the food bowl every time the it heard the sound. 4. In psychological terms, food was the eliciting stimulus and it created a salivary response. This relation was chosen by the food 5. Something that was not food caused a food like response (the metronome). The dog has associated food which causes it to salivate with the metronome C. Thorndike s Procedure-(The Law of Effect) 1. Thorndike s method was different from Pavlov s in that the eliciting stimulus, food was given after the response 2. He had chicks wander through a maze and reach the end. If the chick made it to the end it was rewarded with a piece of food 3. Thorndike measured the time it took the chicks to navigate the maze and realized that the time decreased over successive tries 4. In another example, Thorndike trapped a cat in a puzzle box and allowed it to escape only if it pressed a lever inside the box 5. Over a long period of time, the chicks and/or cats decreased the time it took to accomplish the task 6. Thorndike theorized that the reward created an association between a response and a certain stimulus D. Comparisons Between Pavlov s and Thorndike s Procedures 1. Similarities a. The environment may be regarded as a sequence of stimuli that continuously changes as the learner orients toward different stimuli b. Behavior consists of a continuously changing sequence of responses 2. Differences a. Pavlov: the eliciting stimulus is introduced after another stimulus S bell -S food * b. Thorndike: eliciting stimulus is introduced after a response S-R = S* 3. Implications of the Procedural Difference a. B. F. Skinner realized between the two procedures that Thorndike s procedure opened the possibility of changing the environment of any behavior of which the organism was capable b. He realized that you could change the response behavior of an organism by following a response with an eliciting stimulus c. Skinner realized that the behaviors that came as a result of the elicited stimulus were emitted, they were permitted by the environment with no specific controlling stimulus d. Pavlov s procedure controlled the relation of an environmental stimulus to an eliciting stimulus II. Conditions Required for Learning A. Pavlov s procedure = classical procedure-conditioning procedure in which a neutral stimulus precedes an eliciting stimulus with the result that the neutral stimulus evokes a learned response resembling the elicited response 1. The stimulus that reliably precedes the eliciting stimulus is called the conditioned stimulus (metronome) 2. The eliciting stimulus is called the unconditioned stimulus (the food)

2 3. The response to the unconditioned stimulus is called the unconditioned response (salivation) 4. Over time, the subject will associate the conditioned stimulus to the unconditioned response (conditioned response) B. Thorndike s procedure = operant procedure/instrumental-conditioning procedure in which a response (the operant) precedes an eliciting stimulus 1. Reinforcer-an agent that reinforces a certain response to occur. It causes an appetitive stimulus a. Causes an action to more likely occur b. Primary reinforcers-effective since birth i. Food ii. Water iii. Access to a sexually receptive partner iv. Access to complex sensory stimulation (fireworks) c. Secondary reinforcer-things that we know can get us to primary reinforcer i. Money d. Social reinforcer-things that allow us to get recognition from others i. Praise 2. Punishers-the opposite of a reinforcer. It causes an aversive stimulus a. Causes an action to occur less 3. In operant conditioning, the response becomes stamped in C. Temporal Contiguity-relation between two events that occur close together in time 1.Time plays a factor in learning according to when the eliciting stimulus is given 2. Contiguity in the Classical Procedure a. Forward conditioning procedure CS given before US/UR b. Backward conditioning procedure CS given after US/UR c. Temporal contiguity can change the relationship between the conditioned and unconditioned stimuli d. When the US is followed directly after the CS-known as the delay procedure (best way for learning) e. When the US is followed a short time after the CS-known as trace procedures (the US must be less than.5 seconds long) f. When the US is presented at the exact same time as the CS-known as simultaneous procedure 3. Contiguity in the Operant Procedure a. As the delay interval increases between the operant response and eliciting stimulus, the strength of the operant response declines b. There are so many different responses going on at the same time, that if the eliciting stimulus is given too late, the association will be difficult to make c. Study of temporal contiguity can be inaccurate because other behavioral effects could interfere in the time between the operant response and the eliciting stimulus 4. Schedules of Reinforcement-procedures that manipulate the temporal relation between stimuli, responses, and reinforcers a. There are two types manipulations: response and temporal b. When response requirements are known as ratio schedules, procedures in which a reinforcer is dependent on the occurrence of a number of responses c. When time requirements are known as interval schedules, procedures in which a reinforcer is dependent on the passage of time before the response is effective d. Both types of schedules can be fixed or variable e. The rate of responding is more affected by the schedule on which reinforcers occur than by the mere number of reinforcers f. Reinforcement works only over a short time interval 5. Effects of Temporal Contiguity on Human Behavior a. Phobias result from a severe aversive stimulus which does not have to be necessarily related to the object b. Drug addiction is an example of temporal contiguity in that, when the drug is taken, the person experiencing the effects of the drug (happiness, euphoria) will continue to take it in order to feel those effects

3 D. Behavioral Discrepancy-only a stimulus that evokes a behavioral change can function as a reinforcer 1. Something more than temporal contiguity is required to illicit a response 2. If you are conditioned to one thing in the environment as a conditioned stimulus, you are less likely to produce a conditioned response to another stimulus (pg. 131, behavioral discrepancy) a. The first conditioned stimulus blocks the other conditioned stimulus as long as the first conditioned stimulus predicts the conditioned response 3. Eliciting stimulus functions as a reinforcer only if it evokes a response that is not already occurring 4. The more deprived the learner is of contact from the eliciting stimulus, the stronger the behavior that is evoked by that stimulus when it does appear E. Laws of Association 1. If two events are placed in the same place at around the same time, an association forms (Contiguity) 2. The number of times that the events happen will also create an association (Frequency) 3. The stimuli in creating the behavior must be meaningful (Intensity) 4. In order for something to produce a reliable behavior it must be predictive (Contingency) 5. We are prepared to learn certain things more readily than other things (Preparedness) III. The Process of Learning A. Acquisition-Increase in the environmental guidance of behavior as the result of the either a classical or operant conditioning procedure; the learning of a response 1. Occurs when a response is followed by a reinforcer 2. Acquisition requires habituation, the decrease in responding to a stimulus after that stimulus is repeatedly presented without an important consequence 3. Shaping-procedure in which successively closer approximations to a target behavior are reinforced a. Most learning is more complex and cannot be done with acquisition alone b. Acquisition may require shaping to reinforce successively closer approximations to its final form c. An example would be a rat pressing a lever. The experimenter could provide food to get the rat to the lever, then to get it to press the lever 4. Natural Selection and Learning a. Reinforcement is the process by which individual experience changes the environmental guidance of behavior b. The potential for behavior to be reinforced is a product of natural selection c. Natural selection reinforces individuals to interact with their species, avoid predators, and gather and reproduce d. One example of natural selection affecting learned behavior is by taste aversions i. Let s say an animal eats a lemon and was then injected with nausea caused by lithium chloride, the animal will avoid lemons in the future because it associated lemons with nausea ii. Because all food must enter the mouth smell and taste receptors were naturally selected as a way to tell the animals which foods were harmful and which foods were nutritional iii. Taste aversion is an example in which the conditioned stimulus can reinforce even after a long period of time has passed 5. Conditioned Reinforcement a. Human behavior is often reinforced by stimuli that do not evoke readily detectable responses. Natural selection can act only on behavior that actually occur b. How can stimuli that do not evoke obvious responses serve as reinforcers? c. The answer to this is because of conditioned (secondary) reinforcer, a stimulus that can function as a reinforcer after it has been paired with another stimulus that can already function as a reinforcer i. These reinforcers are conditional based on the individual s experience ii. We associate them with acquiring primary reinforcers 6. Automatic Conditioned Reinforcement-process in which a behavior inherently produces stimuli that function as reinforcers for that same behavior a. This type of reinforcement occurs as you get closer to the target behavior b. If you realize that you are getting close to the target behavior this reinforces approximations to that behavior c. Automatic conditioned reinforcement plays an especially important role in language

4 i. A child will understand the meaning of a word when she sees others using it in context and as a result, will automatically associate the word to the animal B. Extinction-decrease in a learned behavior when the behavior is no longer followed by a reinforcer 1. You are more likely to forget a behavior or action if it is not being reinforced 2. Extinction can be slowed by having less frequent reinforcements this is called intermittent (partial) reinforcement in which not every response is followed by a reinforcer 3. Reacquisition after extinction is generally more rapid than original acquisition 4. Reacquisition and spontaneous recovery, increase in a previously extinguished response after the passage of time, demonstrate that extinction does not completely eliminate the effects of prior learning 5. Depending on which reinforcement schedule you are on will determine the rate of extinction 6. Pavlov believed by presenting the CS with the US it strengthens two parts of the brain and creates a connection. Once extinction occurred, the connection disappeared C. Stimulus Generalization-process by which behavior occurs in an environment in which it has not been reinforced, but which is similar to that environment 1. The effects of reinforcement are not restricted to the specific environment in which learning took place 2. Behavior that has been reinforced in one environment occurs in other environments if the other environments contain stimuli in common with the environment in which the behavior was reinforced D. Stimulus Discrimination-process by which the environmental guidance of behavior is restricted to the environment in which the behavior was reinforced 1. When consequences of behavior change as the environment changes, stimulus discrimination occurs 2. A procedure in which a response has different consequences in different environments is called differential conditioning procedure 3. Contextual discriminations-discrimination procedure in which the stimulus in whose presence the behavior is reinforced varies with the value of another stimulus, the stimulus context 4. Equivalence Classes-a set of physically unrelated stimuli that all control the appropriate behavior without direct training after the stimuli have appeared in multiple contextual discriminations a. Basically, a subject can learn one relationship (we ll call S1-S2) and a similar relationship (S2-S3) and be able to associate all of them together (S1-S3-S2) without further training (see figure 5.16 pg. 140) E. Choice Between Multiple Operants 1. If subjects were given a choice between two reinforcers, the one that would produce more reinforcers per unit of time would be chosen more often. This demonstrates the matching principle, the proportion of responses occurring during a stimulus is the same as the proportion of reinforcers received during that stimulus 2. We distribute our responses between choices; we choose the easier one more often than the other but we will not completely throw out the more difficult behavior/activity F. Punishment-process by which a stimulus decreases the strength of behavior by conditioning responses that interfere with the operant 1. Punishers weaken a certain behavior so that it does not happen as frequently or is completely extinct 2. Punishers elicit escape or withdrawal responses which are responses that terminate or reduce contact with an aversive stimulus 3. The Effects of Punishment a. Punishment can effectively decrease responding but often with undesirable consequences b. These consequences include: risk of injury, inducement of fear and hostility, organisms learn which responses not to make, punishment does not teach the organism desirable responses 4. The purpose of a punisher is to decrease the probability of a response due to the presentation of a punisher after the response 5. Consistent punishment works best in development of a behavior IV. Biological Basis of Reinforcement A. Neural Systems of Reinforcement 1. Both unconditioned reinforcers and conditioned reinforcers activate common reinforcing systems in the brain 2. Over time, the CS will become associated to the UR and the brain will automatically produce the actions necessary for a certain behavior

5 3. The Ventral Tegmental Area (VTA) is a system of neurons whose axons extend far into the forebrain. When activated, they release dopamine which enhances synaptic efficacy, the efficiency of making connections in the brain 4. When a CS is paired with a US, the response eventually is paired with the neuron firing which creates the reinforcement process B. Cellular Mechanisms of Reinforcement 1. Neurotransmitters affect the behavior of a neuron 2. Glutamate is an excitatory neurotransmitter that affects AMPA and NMDA receptors 3. NMDA receptors increase the ability of glutamate from the presynaptic neuron to fire the postsynaptic neuron via AMPA receptors 4. When AMPA receptors are stimulated they cause NMDA receptors to open allowing Ca +2 into a cell allowing another action potential to occur. However, when this occurs a tag forms on the AMPA receptors that have just been stimulated by glutamate which enhances AMPA receptor sensitivity to glutamate 5. When the reinforcer is followed by the stimulus, the dopamine triggers the formation of proteins on the postsynaptic neuron that changes the cell to better facilitate the new behavior because it more likely for the neuron to fire 6. The entire process is known as long-term potentiation (LTP) V. Learning With Experience A. Perceptual Learning-process by which combinations of environmental stimuli acquire control of behavior 1. One example of this was when a rat was to find itself out of a maze 2. Once food was placed in the maze the rat was able to move through the maze faster. This is an example of latent learning, the facilitation of learning after the stimuli that guide behavior have been experienced but without the behavior being reinforced in their presence 3. Perceptual learning is acquired by use of polysensory neurons (neurons that take inputs from more than one sense) to particular combinations of stimuli 4. The hippocampus plays a major role in perceptual learning B. Instructional Control-guidance of behavior by discriminative stimuli, especially verbal stimuli such as directions 1. The way that humans obtain complex behaviors is through instruction 2. Instructed behavior enhances the whole process of reinforcement C. Observational Learning-changes in the behavior of an observer after seeing another learner behave in that same situation 1. Humans learn through instruction but also seeing others behave within certain behaviors 2. Imitation occurs when behavior of the observer corresponds to the form of the behavior of the person being observed 3. Determinants of Imitation a. Consequences of the model b. Characteristics of the model