Behavior or behaviour (see spelling differences) refers to the actions or reactions of an object or organism, usually in relation to the environment. Behavior can be conscious or unconscious, overt or covert, and voluntary or involuntary. In animals, behavior is controlled by the endocrine system and the nervous system. The complexity of the behavior of an organism is related to the complexity of its nervous system. Generally, organisms with complex nervous systems have a greater capacity to learn new responses and thus adjust their behavior. Human behavior (and that of other organisms and mechanisms) can be common, unusual, acceptable, or unacceptable. Humans evaluate the acceptability of behavior using social norms and regulate behavior by means of social control. In sociology, behavior is considered as having no meaning, being not directed at other people and thus is the most basic human action. Animal behavior is studied in comparative psychology, ethology, behavioral ecology and sociobiology.

Because of the many associations with the term, it is difficult to characterize a term like Behavior without specifying a context of discourse in which it is to take on meaning. One such context is Psychology, which has, at various times, been defined as the study or science of behavior. Oddly enough, despite the centrality of the construct to psychology, in regular introductory textbooks, such as Myers, etc. [references to be supplied], a full characterization of the term and its meaning is avoided in favor of an immediate turn to the subject of genetics and the biological basis for all behavior, animal as well as human. This is unfortunate, for whereas discussion of the biological or evolutionary basis of human behavior is important, it would be better if it took place against a backdrop in which the term had achieved some degree of definitional coherence. This is what is being attempted here.

There are, broadly speaking, four categories of human behavior, some of which, it will be seen quickly, overlap with and are probable extensions of animal behavior. The first category may be illustrated as follows. Invoking ordinary language usage, we often say: "she behaved badly" or "he was behaving oddly." In such statements, the term has two attributes. Behavior is something we can see or hear or otherwise detect with our senses. The term is linked to sensation and the manner in which we take in information from our immediate surroundings. By contrast is the term "thinking”—also a subject for psychology—which denotes something typically invisible to an observer. Second, as used in these two examples, the term takes on a normative cast. In the first case, there is behavior that appears to contravene expectations of a moral kind. People who steal are behaving badly. So are people who lie. In the second sense of normativity, there are expectations of a social kind. You do not pick your nose in public (see, though, car drivers at stop lights for exceptions to this generally iron clad rule). You walk in a straight line down the sidewalk. Any 'contraventions' of these norms will lead to the label of odd behavior, though here it is assumed that there is nothing inherently immoral about the behavior in question. So behavior, as the term is often used in ordinary language, connotes norms or expectations, of the moral kind and of the social kind. A synonym in this case might be conduct. Someone who is behaving "badly" may also be said to be conducting himself "badly."

A second category of behavior produces a broad descriptive sweep. It takes in all behavior we might label purposive or goal-driven. In some contexts [ref to be supplied], the term “action” is preferred over behavior, and we say that humans engage in actions, meaning that what we observe about them publicly are behaviors which have an underlying purpose. Seeing someone have lunch in the college cafeteria we are observing the behavior of eating. Had we seen that person earlier in the morning, we might have observed her parking her car in the new structure. A description of her actions in both situations would link them through conversations which would reveal that she is a student at the college: she drives to class in the morning, takes two classes, has lunch, leaves for paid employment in the afternoon, etc. The point of all this is that her actions over a broad range of her day are governed by a sense of purpose, that she is a student and expects to graduate from college in four years with a degree in nursing. While at any point in time it is likely that she does not feel this sense of purpose, that is how she would analyze her actions and make sense of them to a stranger, if asked.

A third category often falls within the second as a sub-category though nevertheless is a domain in its own right. This is the category of performance or skilled behavior. Behavior that demonstrates skills of various kinds from work to sports, from behaviors involving psychomotor motions of the body, e.g. playing tennis, to those involving linguistic and extra-linguistics interactions with others, e.g. a car salesman. Again, we take examples from ordinary language usage. While watching a friend play tennis, we might say: he is playing very badly. If in the same game, he throws his racket on the ground in exasperation, we respond: Now, he’s behaving very badly. So we easily, in our everyday usage, distinguish between behavior that is under the control of or guided by learned skills and behavior that is under the control of or guided by social norms. In any game we are watching, we see players perform skillfully but behave or conduct themselves very badly and vice versa, as when we witness lack of skills on the part of someone who, at the same time, by his (normative) behavior, evokes the spirit of the game. We can dislike the first and admire the second. But again, we distinguish between a repertoire of behaviors that fall under the heading of skill and those that can be labeled socially desirable or undesirable.

Finally, there is a fourth category, which at first sight, seems to belong to the goal-driven domain, since we appear to see goals at work. If so, then the goals are mostly of a ‘low-level,’ physical kind we might term instinctual, having to do with the anatomical or physiological nature of the organism. Behavior in this category is determined by the need or desire to avoid pain and embrace pleasure. Going back to our example of the student in the dining room, part of her behavior is distantly motivated or can be explained by her goal of obtaining a degree. At the same time, that she has chosen to eat certain food but avoid other choices can be explained by what has sometimes been called the “pleasure principle.” There is food that she likes and food that she doesn’t like. Such choices and experiences are often conversation items for friends engaged in eating together. In the movie, the Matrix, the character called Cipher betrays his friends because the lofty goal of embracing reality is too distant to guide him any longer, when he can experience the complex sensuous pleasures of good wine and food, though, as he acknowledges in a scene in a restaurant with two Agents, he knows that none of it is real.

In summary then, behavior is something we ourselves do and something we experience from others. Behavior is sensuous in that what it is can be experienced through one or more of the senses. Lacking this sensational dimension, whatever the “it” is would not constitute behavior. Second, there are four basic categories. Behavior that we term conduct denotes a broad range of activity under the guidance of social-moral norms. Behavior that we term performance denotes a range of activity governed by skill repertoires. Behavior we sometimes term experience refers to actions and choices of action that maximize comfort or pleasure and minimize discomfort or pain. Finally, there is no particular other term for the very broad range of actions that fall under the heading of purposive or goal-driven, behavior that appears dictated by a sense of who we are and what we want to become.

Behavior became an important construct in early 20th century Psychology with the advent of the paradigm known subsequently as "behaviorism." Behaviorism was a reaction against so-called "faculty" psychology which purported to see into or understand the mind without the benefit of scientific testing. Behaviorism insisted on working only with what can be seen or manipulated and in the early views of John B. Watson, a founder of the field, nothing was inferred as to the nature of the entity that produced the behavior. Subsequent modifications of Watson's perspective and that of so-called "classical conditioning" (see under Ivan Pavlov led to the rise of Operant Conditioning, a theory advocated by B.F. Skinner, which took over the academic establishment up through the 1950s and was synonymous with "behaviorism" for many.

For studies on behavior ethograms are used.

See also

• Animal behavior
• Applied behavior analysis
• Behaviorism
• Radical behaviorism
• Experimental analysis of behavior
• Forms of activity and interpersonal relations
• Human behavior
• Human sexual behavior
• Instinct
• Motive
• Normal (behavior)
• Psychology
• Reasoning
• rebellion
• Taboo
• Theories of political behavior
• Work behavior