Behaviorism and mentalism are two theories that involve the mind, but one is based on empirical observation and the other is based on pure belief. Behaviorism is a topic that you learn about in a psychology course, a theory that behaviour is in response to conditioning without regard to feelings, and mentalism, a theory based on mental perception and thought processes, can be learnt through experience or through an apprenticeship with an experienced mentalist.
Behaviorism is a theory that is based around the study of behaviours in humans and animals in response to negative or positive stimulation. One of the most well-known studies in behaviorism is the study conducted by Ivan Pavlov. He observed that, over time, a dog would begin to salivate after hearing a bell ring because the dog associated it with food being placed in front of it. This is an aspect of behaviorism known as classical conditioning, in which the bell ringing, which is a conditioned stimulus, caused a reaction in the dog because of the food, an unconditioned stimulus.
Operant conditioning is another aspect of behaviorism that studies the behaviours of humans and animals that operate on environmental factors that create negative or positive consequences. Also known as response-stimulus, operant conditioning allows the study participant to associate certain behaviours with either positive or negative consequences and learn from these consequences. One example was found by Edward Thorndike, who observed that cats in a puzzle box associated getting out of the maze with a food reward. This positive reinforcement shaped the behaviour of the cats and conditioned them to immediately open the trap door for the reward.
Mentalism is a part of the field of magic that states that phenomena in the physical and psychological realms are performed by magicians who supposedly possess intuitive and mental powers that are highly developed. Some tricks that are a part of mentalism include mind reading and hypnosis. The illusion of a highly developed intuition is meant to convince the audience that the magician has a connection to the spiritual world or that he possesses supernatural powers.
A mentalist can perform a variety of tricks that convince the audience that she has extreme mental powers. Some of these tricks include psychokinesis, fortune telling, spoon bending and mind reading. A mentalist also may try to predict outcomes of games, answer questions without knowing the question or burn stigmata of a secretly selected symbol into her skin. Some tricks may have harmful drawbacks, such as skin burns, explosions or physical injury from full-body contact.