It may help to start this section on methods you can use to change behaviors by offering a definition of behavior. A behavior is something that you do; some action that you take. Conventionally, a behavior is something that you act out physically, such as taking a walk, or smoking a cigarette, or rolling your eyes when your spouse is complaining. However, behaviors can be subtle, non-physical things too. Thinking can be considered a behavior, for instance.
A very few behaviors are directly instinctual and designed into the human condition. An infant's rooting reflex (how it knows to orient its mouth to the breast) is one, and human being's preparedness as infants to learn languages when exposed to them is another. Most other behaviors are learned. Non-instinctual behaviors become established according to the regular principles described in learning theory, that most scientific of all psychological theories.
The principles of learning theory apply equally well to both human beings and animals, because all animals (human beings included) share a common basic design. All animals, from the highest and most complex to the lowest and simplest, have basic needs they need to meet and are designed in such a way so that they know how to meet them. All animals get "hungry" in some fashion and search for food, and all animals know to avoid extremes of temperature, predators or other environmental threats to their continuing existence Another way of saying this is that all animals have in common that their behavior is motivated. Any animal that can be motivated, can be manipulated according to the principles of learning theory, so as to shape the animal's behavior.
There are two types of animal motivation: the motivation to approach something, and the motivation to avoid something. These two opposed orientations are caused by ancient brain systems that most all animals share in common. In learning theory, approach motivations are described as "reinforcing", and avoidance motivations are described as "punishing". Something that an animal desires to approach can be considered to be a reinforcer for that animal, while something the animal desires to avoid can be considered a punishment.
hings don't innately have reinforcing or punishing properties; rather these properties are ones that animals assign to things, each according to its own needs. What is reinforcing to one animal, then, may not be reinforcing to the next. Similarly, what punishes one animal, may not punish another. Animals are born with different temperaments (genetically determined basic personalities and dispositions), and each individual animal's temperament helps determine what they will respond to.
To make things more complicated, there are two kinds of reinforcements, and two kinds of punishments. Unfortunately, the terms used to clarify the type of reinforcement or punishment sometimes confuse people. It's useful to start by thinking of the terms this way: reinforcement increases the likelihood that someone will act the same way in the future. In other words, a person's behavior will increase due to a reinforcer. Punishments, on the other hand, decrease the likelihood that someone will act a particular way in the future. In other words, the behavior decreases. Now the clarifiers: the term "positive," when used to describe a reinforcer or a punishment, simply means that something was presented to the person. You can mentally substitute a "+" sign for the term, and remember that something was added to the situation. In contrast, "negative" means that something was taken away. This time, mentally substitute a "-" sign for this term to help you remember what it means. Combining all of these terms results in the following learning situations: positive reinforcement (presenting something to the person that increases their behavior), positive punishment (presenting something that decreases their behavior), negative reinforcement (taking something away increases behavior), and negative punishment (taking something away decreases behavior). Again, this is a bit confusing to most people, so some real-world examples should help.
In the jargon of learning theory, the things that animals either want to approach or avoid are known as stimuli. A stimulus is something that stimulates an animal, motivating a reaction.
There are two kinds of stimuli in the world: Those that are instinctually motivating to a given animal, and those which are not instinctually motivating but which can become motivating when they become associated (through a process of classical conditioning) with an instinctually motivating stimulus. A good example of an instinctually motivating stimulus (what is called an "unconditioned" stimulus) for most animals (people included) is food. Animals don't need to learn that food is good; they simply know it when they taste it. An animal may initially ignore a range of other potential stimuli, but come to pay a lot of attention to them after they are paired with food, so that they come to indicate that food is on its way. This is what happens when a dog learns to salivate upon hearing a bell ring (because that bell suggests that mealtime is soon), and when fish in a tank rise to the surface in anticipating of feeding when you lift the lid.