Ivan Pavlov in the context of "Physiologist"

Classical conditioning (also respondent conditioning and Pavlovian conditioning) is a behavioral procedure in which a biologically potent stimulus (e.g. food, a puff of air on the eye, a potential rival) is paired with a neutral stimulus (e.g. the sound of a musical triangle). The term classical conditioning refers to the process of an automatic, conditioned response that is paired with a specific stimulus. It is essentially equivalent to a signal.

Ivan Pavlov, the Russian physiologist, studied classical conditioning with detailed experiments with dogs, and published the experimental results in 1897. In the study of digestion, Pavlov observed that the experimental dogs salivated when fed red meat. Pavlovian conditioning is distinct from operant conditioning (instrumental conditioning), through which the strength of a voluntary behavior is modified, either by reinforcement or by punishment. However, classical conditioning can affect operant conditioning; classically conditioned stimuli can reinforce operant responses.

Extinction in psychology refers to the gradual decrease and possible elimination of a learned behavior. This behavioral phenomenon can be observed in both operantly conditioned and classically conditioned behavior. When operant behavior that has been previously reinforced no longer produces reinforcing consequences, the behavior gradually returns to operant levels (to the frequency of the behavior previous to learning, which may or may not be zero).

In classical conditioning, when a conditioned stimulus is presented alone, so that it no longer predicts the coming of the unconditioned stimulus, conditioned responding gradually stops. For example, after Pavlov's dog was conditioned to salivate at the sound of a metronome, it eventually stopped salivating to the metronome after the metronome had been sounded repeatedly but no food came.

Psychology is defined as "the scientific study of behavior and mental processes". Philosophical interest in the human mind and behavior dates back to the ancient civilizations of Egypt, Persia, Greece, China, and India.

Psychology as a field of experimental study began in 1854 in Leipzig, Germany, when Gustav Fechner created the first theory of how judgments about sensory experiences are made and how to experiment on them. Fechner's theory, recognized today as Signal Detection Theory, foreshadowed the development of statistical theories of comparative judgment and thousands of experiments based on his ideas (Link, S. W. Psychological Science, 1995). In 1879, Wilhelm Wundt founded the first psychological laboratory dedicated exclusively to psychological research in Leipzig, Germany. Wundt was also the first person to refer to himself as a psychologist. A notable precursor to Wundt was Ferdinand Ueberwasser (1752–1812), who designated himself Professor of Empirical Psychology and Logic in 1783 and gave lectures on empirical psychology at the Old University of Münster, Germany. Other important early contributors to the field include Hermann Ebbinghaus (a pioneer in the study of memory), William James (the American father of pragmatism), and Ivan Pavlov (who developed the procedures associated with classical conditioning).

Activity theory (AT; Russian: Теория деятельности) is an umbrella term for a line of eclectic social-sciences theories and research with its roots in the Soviet psychological activity theory pioneered by Sergei Rubinstein in the 1930s. It was later advocated for and popularized by Alexei Leont'ev. Some of the traces of the theory in its inception can also be found in a few works of Lev Vygotsky. These scholars sought to understand human activities as systemic and socially situated phenomena and to go beyond paradigms of reflexology (the teaching of Vladimir Bekhterev and his followers) and classical conditioning (the teaching of Ivan Pavlov and his school), psychoanalysis and behaviorism. It became one of the major psychological approaches in the former USSR, being widely used in both theoretical and applied psychology, and in education, professional training, ergonomics, social psychology and work psychology.

Activity theory is more of a descriptive meta-theory or framework than a predictive theory. It considers an entire work/activity system (including teams, organizations, etc.) beyond just one actor or user. It accounts for environment, history of the person, culture, role of the artifact, motivations, and complexity of real-life activity. One of the strengths of AT is that it bridges the gap between the individual subject and the social reality—it studies both through the mediating activity. The unit of analysis in AT is the concept of object-oriented, collective and culturally mediated human activity, or activity system. This system includes the object (or objective), subject, mediating artifacts (signs and tools), rules, community and division of labor. The motive for the activity in AT is created through the tensions and contradictions within the elements of the system. According to ethnographer Bonnie Nardi, a leading theorist in AT, activity theory "focuses on practice, which obviates the need to distinguish 'applied' from 'pure' science—understanding everyday practice in the real world is the very objective of scientific practice. ... The object of activity theory is to understand the unity of consciousness and activity." Sometimes called "Cultural-Historical Activity Theory", this approach is particularly useful for studying a group that exists "largely in virtual form, its communications mediated largely through electronic and printed texts." Cultural-Historical Activity Theory has accordingly also been applied to genre theory within writing studies to consider how quasi-stabilized forms of communication regularize relations and work while forming communally shared knowledge and values in both educational and workplace settings.

Pierre Belon (1517–1564) was a French traveller, naturalist, writer and diplomat. Like many others of the Renaissance period, he studied and wrote on a range of topics including ichthyology, ornithology, botany, comparative anatomy, architecture and Egyptology. He is sometimes known as Pierre Belon du Mans, or, in the Latin in which his works appeared, as Petrus Bellonius Cenomanus. The Russian physiologist Ivan Pavlov (known for Pavlov's dogs) called him the "prophet of comparative anatomy".