Behaviorism (or behaviourism), is an approach to psychology that combines elements of philosophy, methodology, and theory. It emerged in the early twentieth century as a reaction to "mentalistic" psychology, which often had difficulty making predictions that could be tested using rigorous experimental methods. The primary tenet of behaviorism, as expressed in the writings of John B. Watson, B. F. Skinner, and others, is that psychology should concern itself with the observable behavior of people and animals, not with unobservable events that take place in their minds. The behaviorist school of thought maintains that behaviors as such can be described scientifically without recourse either to internal physiological events or to hypothetical constructs such as thoughts and beliefs.
From early psychology in the 19th century, the behaviorist school of thought ran concurrently and shared commonalities with the psychoanalytic and Gestalt movements in psychology into the 20th century; but also differed from the mental philosophy of the Gestalt psychologists in critical ways. Its main influences were Ivan Pavlov, who investigated classical conditioning although he did not necessarily agree with behaviorism or behaviorists, Edward Lee Thorndike, John B. Watson who rejected introspective methods and sought to restrict psychology to experimental methods, and B.F. Skinner who conducted research on operant conditioning.
In the second half of the 20th century, behaviorism was largely eclipsed as a result of the cognitive revolution. While behaviorism and cognitive schools of psychological thought may not agree theoretically, they have complemented each other in practical therapeutic applications, such as in cognitive–behavioral therapy that has demonstrable utility in treating certain pathologies, such as simple phobias, PTSD, and addiction. In addition, behaviorism sought to create a comprehensive model of the stream of behavior from the birth of a human to their death (see Behavior analysis of child development).
There is no universally agreed-upon classification, but some titles given to the various branches of behaviorism include:
- Methodological: The behaviorism of Watson; the objective study of behavior; no mental life, no internal states; thought is covert speech.
- Radical: Skinner's behaviorism; is considered radical since it expands behavioral principles to processes within the organism; in contrast to methodological behaviorism; not mechanistic or reductionistic; hypothetical (mentalistic) internal states are not considered causes of behavior, phenomena must be observable at least to the individual experiencing them. Willard Van Orman Quine used many of radical behaviorism's ideas in his study of knowing and language.
- Teleological: Post-Skinnerian, purposive, close to microeconomics. Focuses on objective observation as opposed to cognitive processes.
- Theoretical: Post-Skinnerian, accepts observable internal states ("within the skin" once meant "unobservable," but with modern technology we are not so constrained); dynamic, but eclectic in choice of theoretical structures, emphasizes parsimony.
- Biological: Post-Skinnerian, centered on perceptual and motor modules of behavior, theory of behavior systems.
- Psychological behaviorism (PB) Arthur W. Staats: First general behaviorism that centers on human behavior. Created time-out, token-reinforcement and other methods, analyses, findings and the theory of that helped from behavioral child development, education, abnormal, and clinical areas—also terming this behavioral analysis in 1963. PB laid the basis for cognitive behavior therapy, provides basic theory and research that unifies emotional and behavioral conditioning, and introduces new avenues for basic and applied behavior analysis.
Two subtypes are:
- Hullian and post-Hullian: theoretical, group data, not dynamic, physiological;
- Purposive: Tolman's behavioristic anticipation of cognitive psychology
Skinner was influential in defining radical behaviorism, a philosophy codifying the basis of his school of research (named the Experimental Analysis of Behavior, or EAB.) While EAB differs from other approaches to behavioral research on numerous methodological and theoretical points, radical behaviorism departs from methodological behaviorism most notably in accepting feelings, states of mind and introspection as existent and scientifically treatable. This is done by identifying them as something non-dualistic, and here Skinner takes a divide-and-conquer approach, with some instances being identified with bodily conditions or behavior, and others getting a more extended "analysis" in terms of behavior. However, radical behaviorism stops short of identifying feelings as causes of behavior. Among other points of difference were a rejection of the reflex as a model of all behavior and a defense of a science of behavior complementary to but independent of physiology. Radical behaviorism has considerable overlap with other western philosophical positions such as American pragmatism. Another way of looking at behaviorism is through the lens of egoism, which is defined to be a causal analysis of the elements that define human behavior with a strong social component involved.
Experimental and conceptual innovations 
This essentially philosophical position gained strength from the success of Skinner's early experimental work with rats and pigeons, summarized in his books The Behavior of Organisms and Schedules of Reinforcement. Of particular importance was his concept of the operant response, of which the canonical example was the rat's lever-press. In contrast with the idea of a physiological or reflex response, an operant is a class of structurally distinct but functionally equivalent responses. For example, while a rat might press a lever with its left paw or its right paw or its tail, all of these responses operate on the world in the same way and have a common consequence. Operants are often thought of as species of responses, where the individuals differ but the class coheres in its function-shared consequences with operants and reproductive success with species. This is a clear distinction between Skinner's theory and S–R theory.
Skinner's empirical work expanded on earlier research on trial-and-error learning by researchers such as Thorndike and Guthrie with both conceptual reformulations—Thorndike's notion of a stimulus–response "association" or "connection" was abandoned; and methodological ones—the use of the "free operant," so called because the animal was now permitted to respond at its own rate rather than in a series of trials determined by the experimenter procedures. With this method, Skinner carried out substantial experimental work on the effects of different schedules and rates of reinforcement on the rates of operant responses made by rats and pigeons. He achieved remarkable success in training animals to perform unexpected responses, to emit large numbers of responses, and to demonstrate many empirical regularities at the purely behavioral level. This lent some credibility to his conceptual analysis. It is largely his conceptual analysis that made his work much more rigorous than his peers', a point which can be seen clearly in his seminal work Are Theories of Learning Necessary? in which he criticizes what he viewed to be theoretical weaknesses then common in the study of psychology. An important descendant of the experimental analysis of behavior is the Society for Quantitative Analysis of Behavior.
Relation to language 
As Skinner turned from experimental work to concentrate on the philosophical underpinnings of a science of behavior, his attention turned to human language with Verbal Behavior and other language-related publications; Verbal Behavior laid out a vocabulary and theory for functional analysis of verbal behavior, and was strongly criticized in a review by Noam Chomsky. Skinner did not respond in detail but claimed that Chomsky failed to understand his ideas, and the disagreements between the two and the theories involved have been further discussed. In addition; innate theory is opposed to behaviorist theory which claims that language is a set of habits that can be acquired by means of conditioning. According to some, this process that the behaviorists define is a very slow and gentle process to explain a phenomenon as complicated as language learning. What was important for a behaviorist's analysis of human behavior was not language acquisition so much as the interaction between language and overt behavior. In an essay republished in his 1969 book Contingencies of Reinforcement, Skinner took the view that humans could construct linguistic stimuli that would then acquire control over their behavior in the same way that external stimuli could. The possibility of such "instructional control" over behavior meant that contingencies of reinforcement would not always produce the same effects on human behavior as they reliably do in other animals. The focus of a radical behaviorist analysis of human behavior therefore shifted to an attempt to understand the interaction between instructional control and contingency control, and also to understand the behavioral processes that determine what instructions are constructed and what control they acquire over behavior. Recently, a new line of behavioral research on language was started under the name of Relational Frame Theory.
Behaviourism and education 
Behaviourism focuses on one particular view of learning: a change in external behaviour achieved through a large amount of repetition of desired actions, the reward of good habits and the discouragement of bad habits. In the classroom this view of learning led to a great deal of repetitive actions, praise for correct outcomes and immediate correction of mistakes. In the field of language learning this type of teaching was called the audio-lingual method, characterised by the whole class using choral chanting of key phrases, dialogues and immediate correction. Within the Problem Based Learning (PBL) environment, students may be encouraged to engage with the learning process and their peers within the group by positive reinforcement from a skilled facilitator to increase positive actions of engagement, contributions and questioning. Negative behaviours e.g. lack of engagement, negative contributions, could be minimized by the facilitator using negative reinforcement. Within the behaviourist view of learning, the "teacher" is the dominant person in the classroom and takes complete control, evaluation of learning comes from the teacher who decides what is right or wrong. The learner does not have any opportunity for evaluation or reflection within the learning process, they are simply told what is right or wrong. The conceptualization of learning using this approach could be considered "superficial" as the focus is on external changes in behaviour i.e. not interested in the internal processes of learning leading to behaviour change and has no place for the emotions involved the process. .
Operant conditioning 
Operant conditioning was developed by B.F Skinner in 1937 and deals with the modification of "voluntary behaviour" or operant behaviour. Operant behavior operates on the environment and is maintained by its consequences. Reinforcement and punishment, the core tools of operant conditioning, are either positive (delivered following a response), or negative (withdrawn following a response). Skinner created the Skinner Box or operant conditioning chamber to test the effects of operant conditioning principles on rats.
Classical conditioning 
Although operant conditioning plays the largest role in discussions of behavioral mechanisms, classical conditioning (or Pavlovian conditioning or respondent conditioning) is also an important behavior-analytic process that need not refer to mental or other internal processes. Pavlov's experiments with dogs provide the most familiar example of the classical conditioning procedure. In simple conditioning, the dog was presented with a stimulus such as a light or a sound, and then food was placed in the dog's mouth. After a few repetitions of this sequence, the light or sound by itself caused the dog to salivate. Although Pavlov proposed some tentative physiological processes that might be involved in classical conditioning, these have not been confirmed.
Molar versus molecular behaviorism 
Skinner's view of behavior is most often characterized as a "molecular" view of behavior; that is, behavior can be decomposed into atomistic parts or molecules. This view is inconsistent with Skinner's complete description of behavior as delineated in other works, including his 1981 article "Selection by Consequences." Skinner proposed that a complete account of behavior requires understanding of selection history at three levels: biology (the natural selection or phylogeny of the animal); behavior (the reinforcement history or ontogeny of the behavioral repertoire of the animal); and for some species, culture (the cultural practices of the social group to which the animal belongs). This whole organism then interacts with its environment. Molecular behaviorists use notions from melioration theory, negative power function discounting or additive versions of negative power function discounting.
Molar behaviorists, such as Howard Rachlin, Richard Herrnstein, and William Baum, argue that behavior cannot be understood by focusing on events in the moment. That is, they argue that behavior is best understood as the ultimate product of an organism's history and that molecular behaviorists are committing a fallacy by inventing fictitious proximal causes for behavior. Molar behaviorists argue that standard molecular constructs, such as "associative strength," are better replaced by molar variables such as rate of reinforcement. Thus, a molar behaviorist would describe "loving someone" as a pattern of loving behavior over time; there is no isolated, proximal cause of loving behavior, only a history of behaviors (of which the current behavior might be an example) that can be summarized as "love."
Behaviorism in philosophy 
Behaviorism is a psychological movement that can be contrasted with philosophy of mind. The basic premise of radical behaviorism is that the study of behavior should be a natural science, such as chemistry or physics, without any reference to hypothetical inner states of organisms as causes for their behavior. Less radical varieties are unconcerned with philosophical positions on internal, mental and subjective experience. Behaviorism takes a functional view of behavior. According to Edmund Fantino and colleagues: “Behavior analysis has much to offer the study of phenomena normally dominated by cognitive and social psychologists. We hope that successful application of behavioral theory and methodology will not only shed light on central problems in judgment and choice but will also generate greater appreciation of the behavioral approach.”.
Behaviorist sentiments are not uncommon within philosophy of language and analytic philosophy. It is sometimes argued that Ludwig Wittgenstein, defended a behaviorist position (e.g., the beetle in a box argument), but while there are important relations between his thought and behaviorism, the claim that he was a behaviorist is quite controversial. Mathematician Alan Turing is also sometimes considered a behaviorist, but he himself did not make this identification. In logical and empirical positivism (as held, e.g., by Rudolf Carnap and Carl Hempel), the meaning of psychological statements are their verification conditions, which consist of performed overt behavior. W.V. Quine made use of a type of behaviorism, influenced by some of Skinner's ideas, in his own work on language. Gilbert Ryle defended a distinct strain of philosophical behaviorism, sketched in his book The Concept of Mind. Ryle's central claim was that instances of dualism frequently represented "category mistakes," and hence that they were really misunderstandings of the use of ordinary language. Daniel Dennett likewise acknowledges himself to be a type of behaviorist, though he offers extensive criticism of radical behaviorism and refutes Skinner's rejection of the value of intentional idioms and the possibility of free will.
This is Dennett's main point in "Skinner Skinned." Dennett argues that there is a crucial difference between explaining and explaining away… If our explanation of apparently rational behavior turns out to be extremely simple, we may want to say that the behavior was not really rational after all. But if the explanation is very complex and intricate, we may want to say not that the behavior is not rational, but that we now have a better understanding of what rationality consists in. (Compare: if we find out how a computer program solves problems in linear algebra, we don't say it's not really solving them, we just say we know how it does it. On the other hand, in cases like Weizenbaum's ELIZA program, the explanation of how the computer carries on a conversation is so simple that the right thing to say seems to be that the machine isn't really carrying on a conversation, it's just a trick.)
— Curtis Brown, Philosophy of Mind, "Behaviorism: Skinner and Dennett"
21st-century behavior analysis 
As of 2007, modern-day behaviorism, known as "behavior analysis," is a thriving field. The Association for Behavior Analysis: International (ABAI) currently has 32 state and regional chapters within the United States. Approximately 30 additional chapters have also developed throughout Europe, Asia, South America, and the South Pacific. In addition to 34 annual conferences held by ABAI in the United States and Canada, ABAI held the 5th annual International conference in Norway in 2009.
The interests among behavior analysts today are wide ranging, as a review of the 30 Special Interest Groups (SIGs) within ABAI indicates. Such interests include everything from developmental disabilities and autism, to cultural psychology, clinical psychology, verbal behavior, Organizational Behavior Management (OBM; behavior analytic I–O psychology). OBM has developed a particularly strong following within behavior analysis, as evidenced by the formation of the OBM Network and the influential Journal of Organizational Behavior Management (JOBM; recently rated the 3rd highest impact journal in applied psychology by ISI JOBM rating).
Applications of behavioral technology, also known as Applied Behavior Analysis or ABA, have been particularly well established in the area of developmental disabilities since the 1960s. Treatment of individuals diagnosed with autism spectrum disorders has grown especially rapidly since the mid-1990s. This demand for services encouraged the formation of a professional credentialing program administered by the Behavior Analyst Certification Board, Inc. (BACB) and accredited by the National Commission for Certifying Agencies. As of early 2012, there are over 300 BACB approved course sequences offered by about 200 colleges and universities world wide preparing students for this credential and approximately 11,000 BACB certificants, most working in the United States. The Association of Professional Behavior Analysts was formed in 2008 to meet the needs of these ABA professionals.
Modern behavior analysis has also witnessed a massive resurgence in research and applications related to language and cognition, with the development of Relational Frame Theory (RFT; described as a "Post-Skinnerian account of language and cognition"). RFT also forms the empirical basis for the highly successful and data-driven Acceptance and Commitment Therapy (ACT). In fact, researchers and practitioners in RFT/ACT have become sufficiently prominent that they have formed their own specialized organization that is highly behaviorally oriented, known as the Association for Contextual Behavioral Science (ACBS). It has rapidly grown in its few years of existence to reach about 5,000 members worldwide.
Some of the current prominent behavior analytic journals include the Journal of Applied Behavior Analysis (JABA), the Journal of the Experimental Analysis of Behavior (JEAB) JEAB website, the Journal of Organizational Behavior Management (JOBM), Behavior and Social Issues (BSI), as well as the Psychological Record. Currently, the U.S. has 14 ABAI accredited MA and PhD programs for comprehensive study in behavior analysis.
Behavior analysis and culture 
Cultural analysis has always been at the philosophical core of radical behaviorism from the early days (as seen in Skinner's Walden Two, Science & Human Behavior, Beyond Freedom & Dignity, and About Behaviorism.)
During the 1980s, behavior analysts, most notably Sigrid Glenn, had a productive interchange with cultural anthropologist Marvin Harris (the most notable proponent of "Cultural Materialism") regarding interdisciplinary work. Very recently, behavior analysts have produced a set of basic exploratory experiments in an effort toward this end. Behaviorism is also frequently used in game development, although this application is controversial.
List of notable behaviorists 
See also 
- Animal training
- Applied behavior analysis
- Behavior modification
- Behavior therapy
- Behavioral change theories
- Professional practice of behavior analysis
- Behavior analysis of child development
- Classical conditioning
- Cognitive revolution
- Dog behaviorist
- Experimental analysis of behavior
- Important publications in behaviorism
- Models of abnormality
- Psychological behaviorism
- The Logic of Modern Physics
- Skinner, B.F. (16 April 1984). "The operational analysis of psychological terms". Behavioral and Brain Sciences 7 (4): 547–81. Retrieved 2008-01-10.
- Baum, William M. (1994). Understanding behaviorism: science, behavior, and culture. New York, NY: HarperCollins College Publishers. ISBN 0-06-500286-5.
- Gazzaniga, Michael (2010). Psychological Science. New York: W.W. Norton & Company. p. 19. ISBN 978-0-393-93421-2.
- Fraley, L.F. (2001). "Strategic interdisciplinary relations between a natural science community and a psychology community" (pdf). The Behavior Analyst Today 2 (4): 209–324. Retrieved 2008-01-10.
- Friesen, N. (2005). Mind and Machine: Ethical and Epistemological Implications for Research. Thompson Rivers University, B.C., Canada.
- Waldrop, M.M. (2002). The Dream Machine: JCR Licklider and the revolution that made computing personal. New York: Penguin Books. (pp. 139–40).
- Staats, Arthur W.; Staats, Carolyn K.: Complex human behavior: A systematic extension of learning principles. (1963) New York, NY, US: Holt, Rinehart & Winston
- Staats, A.W.: Learning, language, and cognition.(1968) New York: Holt, Rinehart, & Winston
- Moxley, R.A. (2004). "Pragmatic selectionism: The philosophy of behavior analysis" (pdf). The Behavior Analyst Today 5 (1): 108–25. Retrieved 2008-01-10.
- Sober, Elliot (1989). "What is Psychological Egoism?" (pdf). Behaviorism 12 (2): 89. Retrieved 2012-12-09.
- Skinner, B.F. (1991). The Behavior of Organisms. Copley Pub Group. p. 473. ISBN 0-87411-487-X.
- Cheney, Carl D.; Ferster, Charles B. (1997). Schedules of Reinforcement (B.F. Skinner Reprint Series). Acton, MA: Copley Publishing Group. p. 758. ISBN 0-87411-828-X.
- Commons, M.L. (2001). "A short history of the Society for the Quantitative Analysis of Behavior" (pdf). Behavior Analyst Today 2 (3): 275–9. Retrieved 2008-01-10.
- Skinner, Burrhus Frederick (1957). Verbal Behavior. Acton, Massachusetts: Copley Publishing Group. ISBN 1-58390-021-7.
- Skinner, B.F. (1969). An operant analysis of problem-solving. pp. 133–57.; chapter in Skinner, B.F. (1969). Contingencies of reinforcement: a theoretical analysis. Appleton-Century-Crofts. p. 283. ISBN 0-13-171728-6.
- Chomsky, Noam; Skinner, B.F. (1959). "A Review of B.F. Skinner's Verbal Behavior". Language 35 (35): 26–58. doi:10.2307/411334. JSTOR 411334. More than one of
- Skinner, B.F. (1972). "I Have Been Misunderstood.". Center Magazine (March–April): 63.
- MacCorquodale, K. (1970). "On Chomsky's Review of Skinner's VERBAL BEHAVIOR". Journal of the Experimental Analysis of Behavior 13 (1): 83–99. doi:10.1901/jeab.1970.13-83. Retrieved 2008-01-10.
- Stemmer, N. (1990). "Skinner's verbal behavior, Chomsky's review, and mentalism". J Exp Anal Behav 54 (3): 307–15. doi:10.1901/jeab.1990.54-307. PMC 1323000. PMID 2103585.
- Skinner, B.F. (1969). Contingencies of reinforcement: a theoretical analysis. Appleton-Century-Crofts. p. 283. ISBN 0-13-171728-6.
- "Ivan Pavlov". Retrieved 16 April 2012.
- Skinner, B.F (31 July 1981). "Selection by Consequences". Science 213 (4507): 501–4. Bibcode:1981Sci...213..501S. doi:10.1126/science.7244649. PMID 7244649. Archived from the original on 2 July 2010. Retrieved 14 August 2010.
- Fantino, E. (2000). "Delay-reduction theory—the case for temporal context: comment on Grace and Savastano (2000)". J Exp Psychol Gen 129 (4): 444–6. doi:10.1037/0096-34188.8.131.524. PMID 11142857.
- Baum, W.M. (2003). "The molar view of behavior and its usefulness in behavior analysis". Behavior Analyst Today 4: 78–81. Retrieved 2008-01-10.
- Fantino, E.; Stolarz-Fantino, S.; Navarro, A. (2003). "Logical fallacies: A behavioral approach to reasoning". The Behavior Analyst Today 4. p.116 (pp.109–117). Retrieved 2008-01-10.
- Dennett, D.C.. "The Message is: There is no Medium". Tufts University. Archived from the original on 11 January 2008. Retrieved 2008-01-10.
- Dennett, Daniel (1981). Brainstorms: Philosophical Essays on Mind and Psychology. Bradford Books. MIT Press. p. 53. ISBN 978-0-262-54037-7. LCCN 78013723.
- Brown, Curtis (2001). "Behaviorism: Skinner and Dennett". Philosophy of Mind. San Antonio, TX: Trinity University.
- Hayes, S.C.; Barnes-Holmes, D. & Roche, B. (2001) Relational Frame Theory: A Post-Skinnerian account of human language and cognition. Kluwer Academic: New York.
- Ward, Todd A.; Eastman, Raymond; Ninness, Chris (2009). "An Experimental Analysis of Cultural Materialism: The Effects of Various Modes of Production on Resource Sharing". Behavior and Social Issues 18: 1–23.
- Jon Radoff (2011). "Gamification, Behaviorism and Bullsh$!". Radoff.com.
Further reading 
- Baum, W.M. (2005) Understanding behaviorism: Behavior, Culture and Evolution. Blackwell.
- Ferster, C.B. & Skinner, B.F. (1957). Schedules of reinforcement. New York: Appleton-Century-Crofts.
- Malott, Richard W. Principles of Behavior. Upper Saddle River, NJ: Pearson Prentice Hall, 2008. Print.
- Mills, John A., Control: A History of Behavioral Psychology, Paperback Edition, New York University Press 2000.
- Lattal, K.A. & Chase, P.N. (2003) "Behavior Theory and Philosophy". Plenum.
- Plotnik, Rod. (2005) Introduction to Psychology. Thomson-Wadsworth (ISBN 0-534-63407-9).
- Rachlin, H. (1991) Introduction to modern behaviorism. (3rd edition.) New York: Freeman.
- Skinner, B.F. Beyond Freedom & Dignity, Hackett Publishing Co, Inc 2002.
- Skinner, B.F. (1938). The behavior of organisms. New York: Appleton-Century-Crofts.
- Skinner, B.F. (1945). "The operational analysis of psychological terms". Psychological Review 52 (270–7): 290–4.
- Skinner, B.F. (1953). Science and Human Behavior (ISBN 0-02-929040-6) Online version.
- Skinner, B.F. (1957). Verbal behavior. Englewood Cliffs, NJ: Prentice-Hall.
- Skinner, B.F. (1969). Contingencies of reinforcement: a theoretical analysis. New York: Appleton-Century-Crofts.
- Skinner, B.F. (31 July 1981). "Selection by Consequences". Science 213 (4507): 501–4. Bibcode:1981Sci...213..501S. doi:10.1126/science.7244649. PMID 7244649. Archived from the original on 2 July 2010. Retrieved 14 August 2010.
- Staddon, J. (2001) The new behaviorism: Mind, mechanism and society. Philadelphia, PA: Psychology Press. pp. xiii, 1–211.
- Watson, J.B. (1913). Psychology as the behaviorist views it. Psychological Review, 20, 158–177. (on-line).
- Watson, J.B. (1919). Psychology from the Standpoint of a Behaviorist.
- Watson, J.B. (1924). Behaviorism.
- Zuriff, G.E. (1985). Behaviorism: A Conceptual Reconstruction, Columbia University Press.
- LeClaire, J. and Rushin, J.P. (2010) Behavioral Analytics For Dummies. Wiley. (ISBN 978-0-470-58727-0).
- Behaviorism entry by George Graham in the Stanford Encyclopedia of Philosophy
- Dictionary of the History of Ideas: Behaviorism
- Books and Journal Articles On Behaviorism
- Wuerzburg University: behaviourism
- B.F. Skinner Foundation
- Cambridge Center for Behavioral Studies
- Skinner's Theories
- APA Behaviour Analysis
- Association for Behavior Analysis
- Theory of Behavioral Anthropology (Documents No. 9 and 10 in English)
- California Association for Behavior Analysis
- Examining Learning From Multiple Perspectives by Michigan State University
- Association for Contextual Behavioral Science
- Behavior Analysis Online Tutorials