Psychology has three main schools of thought, with several subgroups within them. In this essay, psychology is not being limited to specific areas of research, such as biopsychology, psychophysics, or psycho-pharmacology. Psychology, broadly, is the study of mental processes, including consciousness, and their relation to behavior. I will attempt to outline its different schools of thought and how they can all be viewed as equally valid schools within a unified field.

Although philosophers have long written on the subject, with Kant even denying that psychology could ever become a science – ironically, some of his ideas continue to influence experimental psychology – it wasn’t until the physicist Gustav Fechner created a mathematical formula, linking sensation to perception, a distinction made over 2,000 years ago by Aristotle, in the 19^th century that researchers attempted to measure the mind.

A few decades later, Wilhelm Wundt in Germany and William James in America, who could be described as philosophers with a background in physiology and biology, created laboratories to systematically experiment on these ideas. For Wundt, the aim of psychology was, borrowing a metaphor from chemistry, to discover the molecules of the mind. His school was known as “structuralism,” and also “volunteerism,” meaning that he defined “thought” as conscious attention built upon perception and the deliberate attendance to sensation (which is an automatic physiological response that occurs prior to intention). James, a physician by training, considered consciousness in an evolutionary sense, in terms of what it does and how it helps the organism adapt to the environment. This view is called “functionalism.” If consciousness can be compared to light photons, Wundt investigated its particle-like properties, and James its wave-like properties, as he coined the term “stream of consciousness.”

A prominent physicist and physiologist, Hermann Helmholtz, also did systematic investigations on the nervous system and on sensation/perception in the 19^th century. Brucke, who was one of his students, coined the term “psychodynamic theory” to applications of thermodynamic physics to the study of the mind, that is, to psychological energy. 

However, these approaches remained more or less theoretical. Psychoanalytic therapy, based on psychodynamic theory, was created by the Viennese physician Sigmund Freud, who was a student of Brucke. It is commonly thought that his influential ideas arose mostly out of pure speculation biased by in-vogue medical and psychological ideas, but they also stemmed from observations of patients by him and his colleagues, as there was a practical need to treat a problem, especially among upper class females, then called “hysteria” that had no clear remedy.

Since there was no known physical cause of this perplexing class of symptoms, Freud assumed it must have something to do with the mind. But unlike the earlier approaches to psychology, which attempted to study the conscious mind, he came up with theories and methods that probed the un-conscious mind, based on the work of his colleague Breur and his success in treating his patient Anna O. (who called it the “talking cure”).

Psychodynamic theory was really the first force of psychology. Freud boiled human motivation down to two forces, named from Greek: thanatos – the death instinct, which is the desire to return to a state of non-action and non-existence, manifesting in self-destructive and aggressive acts, and eros – the creative principle, or life instinct. His model of personality mostly focused on the latter, dividing childhood into stages of psycho-sexual development. This is important because it catalogues the process by which the id, a biological impulse/drive (characterized by “primary process” thinking, the demand for wish-fulfillment in the present, guided by fantasy and visual imagination) governed by the “pleasure principle” begins to recede beneath our everyday awareness as we grow up and focus on the world outside our own body and its immediate desires.

During the maturation process the id is opposed by the superego (the authoritarian self) in regards to certain pleasure zones of the body, and to maintain a balance between the two there is the ego (the mostly conscious self). The ego develops out of the id, rationally calculates how to gain pleasure and avoid pain, engages in reality-testing (differentiating imagination from reality), finds ways of releasing of tension and gratifying desires for outward objects in a way that does not violate taboos or thwart future goals. Too much fixation, or cathexis, on an object of pleasure or too much repression of a desire both unbalance the personality. The conflict between the id and the superego happens unconsciously. 

To understand this hydraulic view, you must place Freud’s theory in context. A common assumption in his time was that the energy in the body was like a dynamo or closed electrical circuit. The brain was less understood than it is today, but it was known to be the source of mental processing. As the current flows through the body it is purely biological, and when it goes into the brain it becomes psychic energy. Psychic energy has to regulate physiological drives, and sometimes there is conflict. Anxiety occurs when the libido (sexual energy) cannot express itself. Basically, neurosis (mental imbalance) is bottled up energy. Certain behaviors called “defense mechanisms” diffuse this tension like an engine letting off steam.

However, defense mechanisms can themselves cause problems and disrupt daily life. Freud thought that this inner conflict was the inevitable result of civilization. Since we have to cooperate with others and delay physical gratification, we must gain control of our ids. Authoritarian pressure becomes internalized as the superego. The ego has to find a way to satisfy id drives without breaking the rules of society.

The type of patient suited for psychoanalysis is someone with an overdeveloped superego and underdeveloped ego strength, and the task of the psychotherapist analyst is to form an alliance with the patient’s rational ego. It typically starts off with free-association (saying the first thing that pops into awareness). Not only is the content of the conversation important, but the therapist has to pay careful attention to what the patient does not say. The patient’s dreams also provide material for analysis (for Freud, dreams are the “royal road to the unconscious” because they are a repository of id and superego interactions, largely unmediated by the ego, which speak in the language of visual symbols). In subsequent sessions the therapist can gain a clear sense of what issues the patient is avoiding.

Usually the patient recounts past traumas, often relating to sex, with parents in childhood (real or imagined, fantasized about in a taboo way that is deliberately repressed). For example, males are said to go through a conflict called the “Oedipus complex” in which boys develop a sexual attraction to their mothers and jealousy of their fathers. Fearing punishment from the father, they suffer “castration anxiety,” taking away their source of pleasure. (The anxiety is handled well if the boy can properly forget this urge and eventually identify with his father. If not, both the sexual desire and the fear of its consequences boiling down below will continually disturb the surface of his consciousness). 

A problem at any stage of psycho-sexual development causes a fixation at that stage of development, affecting the later adult personality. After going through certain stages, where the pleasure of tension & release has its locus in the anus, mouth, and phallus (or a desire for one), the normal child has a latency stage in which he or she identifies with the same sex parent and learns to fulfill social roles. When puberty hits, sexual feelings reawaken, and if handled well one reaches the mature genital stage as an adult.

If there are no debilitating neurotic symptoms, the adult can direct impulses into work and love (through marriage and family, of course). The healthy ego directs id drives into socially acceptable, useful pursuits (“sublimation” - the healthiest defense mechanism) without having to think about their selfish basis or worry too much about them. Otherwise, one will exhibit exaggerated behaviors resulting from defense mechanisms.

As the patient is unaware of the source of his anxiety, and thus has no idea why he/she reacts the way they do to features in his/her environment that bother him/her so much, there is a need for uncovering techniques in therapy. One common defense mechanism is “regression” in which the person reacts to a stressful situation by returning to a mental state prior to inner conflicts. This can be observed in a child-like affect or in childish behavior. A crucial task of the therapist is the analysis of “transference,” remaining aloof as the patient eventually directs hostility (or affection, dependence, etc.) towards the therapist, treating him like a parent figure. Then, the therapist interprets this behavior as it presents itself, and the patient can gain insight.

Traditionally, during sessions the analyst would remain out of the patient’s view while they lie on a couch. This was done because, first, Freud, who had learned about hypnosis (which led him to further investigate the unconscious), knew that relaxation was a key part of the process. Second, he believed transference couldn’t occur unless the personality of the therapist faded into the background. Therapy is rarely done like this today, as it is assumed that we can access material without having to go through an intensive free-association procedure.

Although Freud came from a medical background, this talking cure was not like other procedures doctors engaged in. Initially the province of psychiatrists, medical training was eventually dropped as a prerequisite to psychoanalytic training. In addition to learning the method in the textbook sense, training requires the therapist to undergo the treatment him or herself. This is done to prevent “counter-transference,” which is when the therapist interprets the patient’s situation in light of his or her own issues, interfering with the patient’s ability to relive past events, urges, and feelings. (Interestingly, since Freud first systematized this technique, he himself did not have another therapist to analyze him, so he analyzed himself.)

Psychoanalysis is not a cut and dry process and it lacks a definite timetable. This can deplete one’s financial, physical, and emotional resources, so the patient must be very dedicated in order for it to succeed. Furthermore, the problems addressed in psychoanalysis usually affect the upper-classes. In this theory, only the well socialized can develop these defense mechanisms, so this therapy primarily benefits the “worried-well.” Coincidentally, since this therapy was expensive, only the well-to-do can afford it.

For these reasons, some skeptics accuse psychoanalysis of ignoring the plight of those who need real help. Freudians have two main counter-arguments. 1.) Psychotherapy can only be done on those who can benefit from it. It is not the job of psychology to deal with larger social problems; most social problems are best left for the law to handle. 2.) Psychotherapy won’t work if it isn’t done to the fullest extent. If therapy stops before the needed insight occurs, all that money and time will be wasted without any benefit. It’s not like the improvement comes in stages, insight either happens or it doesn’t. If the id is over-exposed too early, the patient will be even worse than before the therapy started.

Besides its high costs and imprecision, another criticism of psychodynamic theory is its negative and deterministic view of human nature. In evaluating the influences of 19^th century science, one cannot leave out the influence of Charles Darwin. With Darwin’s discovery of biological evolution, we are confronted with the fact that the survival of an animal species depends on its success in sexual reproduction, and therefore, many behaviors and rituals exhibited by organisms are merely adaptations to meet that goal. In other words, the sexual drive, just like hunger, thirst, or aggression, is genetically hardwired and controls us. Though there are instances of altruism, our motivation is always based on self-preservation or leveraging an advantage in the environment (e.g. if I help someone now, I expect that person to return the favor in the future, and I may gain other possible benefits afforded by a strong ally, status, etc.).

The incorporation of this view in the social sciences is known as sociobiology and evolutionary psychology, which some theorists, though by no means all, have used to justify hierarchical or authoritarian social structures. Politically, this philosophy is represented by the conservative position that holds that humans are basically selfish and institutions need to keep order through strict punishment to keep people disciplined. If we jeopardize institutional order, violent upheaval and anarchy will ensue. As for Freud, he did have reservations about the unhealthy attitudes of Victorian bourgeois society towards sexuality, but he was not as liberal as many of his successors or detractors in the social sciences.

Another problem is that psychoanalytic ideas seem to be built on a pseudo-scientific foundation. We know that the brain is an organ that can conduct electrical impulses, of course, and thus it can be analyzed in terms of electrodynamic physics, but why smuggle the mind into that electical field as though it is some magical force operating in the body? It's reminscient of the dismissed idea of “phlogiston” in chemistry.  

And what if biological determinism isn’t the whole story? What if human behavior is not “driven” by inner forces at all, but is shaped by the environment, and can be altered or redesigned? These concerns led to the development of learning theories and the school of behaviorism - the second force of psychology.

One of the earliest theorists in experimental psychology, and also the first to systematically use animal research, was Thorndike, who formulated a “law of effect” between stimuli and response (the rate of response to a stimulus will likely increase if it is satisfying to the organism, and decrease if it is not). Independently, a Russian physiologist named Ivan Pavlov had paired a salivating reflex in a dog to a ringing bell, or “conditioned reflex.” If pairing two normally unrelated variables, such as meat powder with the tone of a bell, can cause a reaction from one stimulus to another, then that means, with training, automatic reactions can be shaped into different actions. John B. Watson took these developments and created a whole new direction for psychology that dominated the field for decades.

Whereas Freud has been called a “biologist of the mind,” Watson, an engineer by training, can be considered a “mechanic of the mind” (actually, a strict behaviorist would consider the word “mind” to be nothing more than a verbal designation, rather than an empirical reality that can be studied). While Freud's concept of the superego included the conscience, which pressures us to fear punishment of bad behavior (or, operating through shame and guilt, punishes us after), and the ego ideal, which is pride and self-esteem associated with good behavior, this is still interpretive. It is easier and more scientific, to behaviorists, to simply study the environment and the organism's responses to it, directly observing how rewards and punishments condition behavior.

Thus, behaviorists attempted to eliminate all the imprecise methods they saw in the previous approaches to psychology. To this day, these hypotheses and theories are the easiest to test, especially in animal experiments and controlled single case studies.

However, behaviorism is a very narrow approach. In scientific procedure, behaviorism is elegantly simple and effective. Techniques from classical conditioning have been shown to be effective in therapies targeting phobias. Operant conditioning, based on the reinforcement principles of B.F. Skinner, has been usefully applied in a wide variety of settings, such as in schools, juvenile detention centers, with sports teams, business, animal training, and for those with developmental disorders. As a theory of psychology, however, behaviorism is limited because there is no understanding of underlying cognitive processes.

The problem is that behaviorism, with its own techniques, does not necessarily describe all human activities or preferences. Even in some primate studies, certain behaviors have been observed seemingly independent of external reinforcers (indicating the existence of intrinsic motivation).

Of course, behaviorists only sought very basic principles of learning that apply to all organisms. However, the role of memory cannot be dismissed. For example, an experiment was done in which mice were led through a maze and did not move or do anything except see where they were being pulled on a cart. When left to roam around, they were able to follow the same path that they were led through, even though their behavior was not shaped or reinforced. This shows that the mice internalized the information.

The study of memory gained traction with the publication of the paper “The Magical Number Seven, Plus or Minus Two” by George Miller in the 1950’s, a study on the capacity of working memory and short-term storage. This marks the era of the cognitive revolution in psychology, which later led to the independent branch of cognitive science, a multi-disciplinary field comprising psychology, computer programming, neuroscience, anthropology, and linguistics that studies intelligence and internal learning systems. This research has cross-pollinated with the field of AI (artificial intelligence). Further, there was revived interest in researching the problems of perception and pattern recognition, influenced by “gestalt” (whole-field) psychologists several decades earlier, who argued that we innately perceive figures/objects as wholes and patterns prior to its individual parts (that is, mental or “top-down” processing).

Pure behaviorists argue that if researchers kept pursuing traditional methods it would eventually yield better information. Currently, most theorists combine both approaches for a more complete picture of learning and memory, called Cognitive-Behaviorism. In therapy, it is especially effective to reinforce both adaptive behavior and positive schemata (mental representations) of the world in order to counter self-defeating emotional/behavioral patterns.