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Learning
- Learning is defined as a long-lasting change in behavior resulting from experience. Brief changes in behavior are not considered learning.
- Neuroplasticity, also known as brain plasticity and neural plasticity, is the ability of the brain to change throughout an individual's life, e.g., brain activity associated with a given function can be transferred to a different location, the proportion of neurons can change, and synapses may strengthen or weaken over time
- Long-term potentiation (LTP) is a persistent strengthening of synapses based on recent patterns of activity. These are patterns of synaptic activity that produce a long-lasting increase in signal transmission between two neurons.
- Classical conditioning involves forming an association with some sort of already naturally occurring event.
- Described by Ivan Pavlov and involves placing a neutral signal before a reflex or involuntary behavior (e.g., blinking, salivating, muscle tension).
- Ivan Pavlov made some interesting observations about learning; coined classical conditioning.
- Unconditioned stimulus: The original stimulus – the food.
- Unconditioned response: The response towards that unconditioned stimulus – the salivating.
- Neutral stimulus: A stimulus that has no conditioned response – a bell.
- Conditioned stimulus: What the organism has learned to pair – the bell.
- Conditioned response: The response from the conditioned stimulus.
- Delayed conditioning: Acquisition will occur fastest if the bell is rung, and while it is still ringing, the dogs are presented with food.
- Trace conditioning: During trace conditioning, the CS and US do not overlap. Instead, the CS begins and ends before the US is presented. The stimulus-free period is called the trace interval or the conditioning interval.
- Simultaneous conditioning: the CS and US are presented and terminated at the same time.
- Backward conditioning: US is presented first and is followed by the CS. This is very ineffective.
- Acquisition: Learning has taken place once the animal responds to the CS without a presentation of the unconditioned stimulus.
- Extinction: The process of unlearning behavior. Extinction has taken place when the CS no longer exhibits a CR (bell no longer causes salivation).
- Spontaneous recovery: Sometimes, after a CR has been extinguished and no further training has taken place, CR will appear in the presence of the CS.
- Generalization: Animals may come to generalize the sound of the bell with other stimuli, like a tuning fork or a whistle.
- Discrimination: Animals can be trained to discriminate between stimuli, responding to a bell and not a whistle.
- John B. Watson:
- Little Albert and Aversive conditioning
- 实验大纲.jpg
- Aversive conditioning is commonly used: people who paint their nails with a terrible tasting material to stop themselves from biting their nails is a form of aversive conditioning.
- First order conditioning is the regular process of pairing a neutral stimulus with an unconditioned response (bell with salivating).
- Second order conditioning is pairing another neutral stimulus (a light) with the previously conditioned stimulus (the bell) in order to eventually make the light a conditioned stimulus.
- 铃响(NS) + 食盆(US) → 狗激(UR) ： 铃(响CS) → 狗激(CR)
- （更牛逼的）*铃响(CS) + 灯亮(NS) → 狗激(CR) ： 灯亮(CS) → 狗激(CR)
- Learned Taste Aversions: If you ingest an unusual food or drink, and then you become nauseous, you’ll most likely develop an aversion to that particular food.
- In some therapeutic settings, therapists give alcoholics a drinking containing a nausea-producing drug.
- John Garciaand Robert Koelling illustrate how rats more readily learned to make certain associations than others.
- They made rats learn that a noise would be paired with a shock and an unusual-tasting water with nausea.
- However, the rats were unable to make the connection between unusual tasting water and the shock.
- Edward Thorndike Experiment
- The law of effect states that if the consequences of a behavior are pleasant, the stimulus-response (S-R) connection will be strengthened and the likelihood of the behavior will increase.
- If the S-R connection is unpleasant, the likelihood of the behavior will decrease.
- Operant conditioning is a learning process through which the strength of a behavior is modified by reinforcement or punishment.
- First described by B. F. Skinner, an American psychologist. Involves applying reinforcement or punishment after a behavior.
- Behavior is either strengthened or weakened by reinforcement or punishment.
- Reinforcer/reinforcement: Anything that makes a behavior more likely to occur is a reinforcer.
- Positive reinforcement refers to the addition of something pleasant. For example, food, shelter, water.
- Negative reinforcement removing something unpleasant. For example, a loud noise, darkness, pain.
- Punishment is anything that makes a behavior less likely to reoccur.
- Positive punishment: Adding an aversive stimulus to decrease behavior. For example, a shock.
- Negative punishment (omission training): Removing a pleasant stimulus to decrease behavior. For example, taking away a child’s toy.
- Escape conditioning (escape learning) occurs when an aversive stimulus is presented and an animal responds by leaving the stimulus situation.
- Avoidance conditioning (learning) enables one to avoid the unpleasant stimulus altogether.
- Both escape and avoidance conditioning are types of negative reinforcement, both result in an increase of the behavior that terminated or avoided the aversive stimulus.
| Reinforcement: Increases/Maintains Behavior |
Punishment: Decreases Behavior | ||
| Positive (add stimulus) |
Add a pleasant stimulus to increase/maintain behavior | Add an aversive stimulus to decrease behavior | |
| Negative (remove stimulus) |
Remove aversive stimulus to increase/maintain behavior | Remove pleasant stimulus to decrease behavior |
- Shaping reinforces the steps used to reach a single desired behavior.
- The goal of shaping is to mold a single behavior (e.g., a bar press by a rat).
- Chaining: Involves reinforcing individual responses occurring in a sequence to form a complex behavior.
- For example, rewarding an animal after completing an obstacle course.
- The goal of chaining is to link together a number of separate behaviors into a more complex activity.
- Primary reinforcers things like food, water, rest, sex. They are rewarding generally because they help the organism survive.
- Secondary reinforcers are things that the organism has learned to have value. For example, saying thank you, getting good grades, showing up on time, etc.
- Money is called a generalized reinforcer because it can be traded for virtually anything.
- Reinforcement differs between individuals.
- Premack Principle: Whichever of two activities is preferred can be used to reinforce the activity that is not preferred.
- Schedules of reinforcement are the rules that determine how often an organism is reinforced for a particular behavior.
- Fixed Ratio: Reinforcement is delivered after a fixed number of responses (press this lever 40 times and you get…).
- Fixed Interval: Reinforcement is delivered after a behavior is performed following the passage of a fixed amount of time.
- Variable ratio: Reinforcement is delivered after a variable number of responses (this is how slot machines work – sometimes they pay out on the first pull, sometimes after hundreds).
- Variable interval: Reinforcement is delivered after a behavior is performed following the passage of a variable amount of time.
| Fixed Interval | Reward on fixed time basis | Leads to average and irregular performance | Fast extinction of behavior |
| Fixed Ratio | Reward tied to specific number of responses | Quick and stable performance | Moderately fast extinction of behavior |
| Variable Interval | Reward given after varying periods of time | Leads to moderately high and stable performance | Slow extinction of behavior |
| Variable Ratio | Reward given for some behaviors | Quick and stable performance | Very slow extinction of behavior |
- Albert Bandura
- Observational Learning: People and animals learn through observing others.
（看看你的。） - Modeling has two components: observation and imitation.
- (Robert) Rescorla's Contingency model of classical conditioning reflects a cognitive spin on classical conditioning, positing that it is necessary for one event to reliably predict another for a strong association between the two to result – while Pavlov's model holds that the strength of an association between two evens is closely linked to the number of times they have been paired in time.
- Abstract learning involves understanding concepts such as a tree or different rather than just learning to peck at a disk in order to secure a reward.
- Pigeons have been shown a particular shape (square or triangle) and rewarded in one series of trails when they picked the same shape out of two choices. Suggests that pigeons can understand concepts rather than just S-R connections.
- Edward Tolman conducted an experiment with three sets of rats.
- The first set was rewarded for completing a maze.
- The second set never received any rewards.
- Third set was not rewarded during the first half of the trials.
- The third group's performance was very similar to the second group – slow. However, the third group's performance improved dramatically and suddenly once it began to be rewarded for finishing the maze.
- The third group of rats learned their way around in the first trials, but their performance did not improve because they was no incentive to run the maze quickly.
- Tolman suggested that the dramatic increase in performance was due to the rats making a mental map of the maze during the first trial and then used this knowledge once they were aware that they'd be rewarded.
- Wolfgang Kohler and Insightful learning
- Insight learning occurs when one suddenly realizes how to solve a problem.
- Kohler argued that learning often happened in this sudden way due to insight rather than because of the gradual strengthening of the SR (stimulus-response) connection.
