History sucks sometimes, particularly because it’s not entirely accurate (note: why "his" is underlined). But, it is very important to take note of the beginning foundations of a topic before jumping toward the end.

Scientific study of the mind gained popularity during the 19th century, and by the end of the 20th a number of schools of psychology had been established. Several methods developed during these early periods are still relevant and in use today.

Psychophysics

Historically, the general goal of psychophysics is to determine the precise mathematical relationship between stimulus properties and sensations. This approach began with attempts to determine the relationship between stimulus properties and the resulting mental experience they produced. This sort of study can be performed by systematically testing controlled stimuli. Using this controlled technique, we can decipher different features of the nervous system... If you have ever taken a psychology course you have probably heard of the “just noticeable difference” phenomenon.

Gustav Fechner (1801-1887)

Fechner was the first to successfully investigate the Just Noticeable Difference, which is exactly as it sounds; the smallest detectable difference in a changing stimulus. A great example of this, often used by professors, is the lighting in a room. Lets say we start in a room with two candles, then we continue to light more. How many candles does it take for us to notice a difference?

Well, you might be wondering what variables come into play; however, the just noticeable difference corresponds to one law- Weber’s law.
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Weber’s Law: Detected changes in a stimulus properties are proportional to the original magnitude of the stimulus. This is true for the just noticeable difference in sound, weight, candle brightness, etc.

Is Intelligence Hereditary?

Francis Galton (1822-1911)

This guy was really important in the development of statistical applications to psychology. He was renowned as a hereditary “genius” who suggested that eminent people tend to be related to other eminent people. Moreover, he believed that an eminent father was more likely to have an eminent son than an eminent grandfather was to have an eminent grandson. From his observations, he developed Galton’s Law - which states that each child receives 50% heritage from each parent, and 25% from grandparents, etc. With the backing of Dawrinism, Galton’s theory flourished in society as selective breeding was perceived as an advancement.

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Hermann Ebbinghaus (1850-1909)

Herman was the first to gain recognition for plotting forgetting curves; he was able to describe human learning in mathematical terms. He brought attention to the possibility that human cognition could be studied experimentally, and that quantitative results were possible.

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Introspection

This is probably a term most of us have heard by now. Introspection is the examination of one's own conscious experience (thoughts and/or feelings). Psychologically speaking, this process relies exclusively on observation of one's mental state, however spiritually it can refer to the examination of the soul. Back in the day, psychologists argued that introspection could in fact be the psychological method; however proper introspection was more than just self-observation. There is always the likelihood of stimulus error.

Stimulus error can be a result of perceiving an overall meaning of a stimulus with disregard to its actual parts. Thus, it is essential that the elemental parts of an experience are accounted for when processing the overall sum of perception. As a result of this possibility, introspection as a research method has been deemed unreliable. With time, other psychological means were developed in order to achieve insight into mental processes and behavior.

The rise of the 20th century brought different schools of psychological thought, most of which opposed earlier approaches of studying mental processes.

Rejection of the introspective method could be observed both in the up and coming Freudian theory and Behaviorism. Freudian theory took things a step further, focusing on the deeper realms of the mind that cannot always be consciously processed, while Behaviorism rejected the study of mental processes all together.

Sigmund Freud (1856-1939)

Freud suggested that we do not know the insights and motivations for our own behavior, rather it all takes place on an unconscious level. He was the first to conceptualize the structure of the mind, which many of us associate with the iceberg image. He presented psychodynamics as the associations between the mind in three distinctions; Id, Ego, and Superego.

Id: operates according to pleasure and instinct
Ego: operates according to reality
Superego: operates on one's morality/conscience

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He also suggested that the development of personality occurred in psychosexual stages (oral, anal, phallic, then finally genital). Freud has a reputation for his fixation on sexual concepts.
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Behaviorism

Behaviorism stemmed from the belief that the mental process is too vague to render tangible results via scientific investigation. Even some extremists promoted Methaphysical behaviorism, which denies the existence of consciousness or mental events. Therefore, behaviorists suggested that the only realistic subject matter was behavior itself. This enabled the development of comparative psychology, which is essentially achieved via human vs. animal comparisons.

John Watson (1878-1958)

Watson believed that conditioning was the cause of every observable behavior. His theory was that through conditioning, habits, whether emotional, manual, or verbal, were learned and reinforced.

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“Give me a dozen healthy infants, well-formed, and my own specified world to bring them up in and I’ll guarantee to take any one at random and train him to become any type of specialist I might select—doctor, lawyer, artist, merchant-chief and, yes, even beggar-man and thief, regardless of his talents, penchants, tendencies, abilities, vocations, and race of his ancestors. (Watson, 1930)”

There are some problems with Behaviorism that must be acknowledged.

Learning occurs even in the absence of stimulus-response. An example of this can be observed in a study performed by McNamara, Long, and Wide (1956).

Rats were exposed to a T-maze in one of two ways: the rats in one group ran the maze themselves, while the rats in the other group were pushed through the maze in little carts by experimenters (so cute). Both groups of rats learned the T-maze. Behaviorism would predict differences in learning, because the second group lacked stimulus-response learning (physically scurrying through the maze to learn it).

Additionally, learning occurs in the absence of reinforcement. This was presented in a study performed by Tolman and Honzik (1930), who had built a complex maze for three groups of rats to run through. The first group was reinforced with food each time they completed the maze, the second group was never reinforced, and the third group was not reinforced until the 11th trial. The results indicated that the rats who learned without reinforcement made the least errors in the maze throughout the duration of the experiment, followed by the continuous reinforcement group.
Moving forward…

Language & Information Processing

Noam Chomshy (1928- )

Before Noam, it was argued that language was a learned through reinforcement. Chomsky disagreed with this, arguing that language is generated creatively; this can be observed by children who speak novel sentences in which they have never been exposed. Thus, Chomsky suggests that humans obtain innate language acquisition. This concept opposes behaviorism in the belief that language is controlled by an internal set off rules, not by external stimuli. This approach is intertwined with the cognitive revolution, which undoubtedly is inspired by the computational technology. Our understanding of information processing was drastically influenced by the parallels of computer processing techniques.

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Noam on Anarchism...

Donald Broadbent (1926-1993) came up with a model of the mind as a biological information processor. He suggested that the mind has a limited number of processing systems, all of which can be better understood through investigation of information processing, transfer, and storage. This is a good note to end on, because it is a relatively modernized approach to psychological thinking which encouraged neuroscientific approaches similar to computer models when conceptualizing mind mechanics. Plus, I'm starting to get hungry and I need to take a break; sorry Broadbent, you don't get a photo :(

More later on...