Category: psychology

Ebbinghaus was the first modern researcher to systematically study memory. He was inspired in part by the work and writings of Fechner. Ebbinghaus was interested in associations (a philosophy or theory of the day that stated that people learn, remember, and organize concepts by ideas being attracted to each other in the mind much in the same way that physical objects are attracted to each other through the laws of magnetism or gravity.

Once Ebbinghaus discovered the work of Fechner he started formulating ideas for research into human memory. He was still interested in associations but needed a way to experimentally research learning and memory. Ebbinghaus started using short nonsense syllables and serial learning to test associationism. He discovered that people (i.e., himself – he was his own and only research participant) could only remember about 7 of the nonsense syllables from a series when only being allowed 1 repetition. George Miller in the mid-1900s investigated this further and showed that humans can only hold 7 (plus or minus 2) words or “chunks” or information in active memory. Ebbinghaus was also famous for establishing a forgetting curve for newly-learned nonsense syllables. Without any relearning or repetition people quickly forgot learned stimuli (down to less than 40% retention within 1 day) but could still remember about 20% 31 days later. Ebbinghaus’ research of memory spurred the large field of memory research that we have today.

Wilhelm Wundt is usually viewed as the first psychologist to set up an experimental laboratory. By doing so, Wundt was trying to establish psychology as a legitimate science, separate from philosophy. He wanted to show that researchers could have well-controlled psychological experiments and systematically measure human behavior. With his work he did not seek to rule out non-experimental aspects of psychology, he just tried to establish that at least some aspects could be measured in a laboratory.

One key component of behavior that Wundt measured in his laboratory was reaction time, which he called mental chronometry. Wundt became interested in reaction time as a student of Helmholtz, who was the first to measure the speed of nerve reflexes. Wundt wanted to know how the brain related to basic nerve transit speed by testing reaction times. Wundt’s lab was able to incorporate the research of many scientists (including Donders’ subtractive method, which expanded on simple reaction times by establishing a reaction time baseline and then complicating the task by adding tasks) and use it to further our knowledge about psychophysiology.

Wundt’s greatest accomplishment was the establishment of his laboratory, which not only produced a lot of research but also trained a lot of future psychologist researchers, many of whom came from America. These trainees went on to other universities and established their own labs; some much like Wundt’s but with what they thought were improvements. Now, psychology labs are ubiquitous on university campuses. Much of Wundt’s writings have not been translated into English, so we (at least outside of German-speaking countries) do not know the entire significance of his work.

Fechner is considered by many to be the first experimental psychologist. It is more accurate to say that he was likely the first well-known and modern experimental psychologist. In any case, he was the first to publish a widely-read experimental psychology textbook. He was more than a writer though. He conducted a series of experiments investigating the nature of human sensation and perception. He even partially blinded himself by staring too much at the sun during studies about visual afterimages. His various studies solidified him as the premiere psychophysicist of the day.

Fechner was greatly interested in applying mathematics to various bodily sensations and perceptions. He believed that he could accurately measure the workings of the brain by measuring the perceptions of the body. Fechner built a lot on the work of Weber, who formulated Weber’s law (jnd/S = k), a law that calculated the difference in the mass of weights required for a person to sense a difference. Fechner expanded on this by recalculating Weber’s law as S = k log R. Briefly the equation represented the relationship between sensation (S) and the size or mass of a stimulus. Like Weber, he believed that there was a threshold that had to be crossed in order to perceive a difference in sensations. Fechner was the first psychophysicist to talk about an absolute threshold, where a stimulus was first noticed. Once a stimulus was noticed, each “just noticeable difference” of the stimulus (i.e., each time, with increasing size or mass of stimuli, that a person can perceive a difference) was termed a difference threshold by Fechner. He also came up with experimental methods for establishing thresholds in laboratory settings. The method of limits is a method in which a stimulus is presented either above or below threshold and then decreased or increased, respectively, systematically to a point where it crosses the absolute threshold. So, Fechner is usually regarded as the first modern experimental psychologist (some of his methods are still employed today). He not only built on Weber’s law but also greatly expanded the field of psychophysics.

Clinical neuropsychologists and all psychologists use various methods to understand normal human behavior and brain-behavior relationships. One common way of understanding behavior is by the clinical method, which is basically using abnormal behavior to make inferences about normal behavior. Neuropsychologists often study people with known brain damage or with abnormal behavior and then study their brain post-mortem (this can also be done in vivo now with MRI and other neuroimaging techniques). The clinical method is important because it is one way phrenology is easily disproven.

Phrenology started out as a good idea. Franz Gall was a physician and anatomist. He was a careful scientist and, for his day, an unmatched anatomist. Phrenology started out as the localization of intellectual and emotional functions to various regions of the brain, which idea was partially supported by later research. However, with flawed methods, Gall assumed that what occurred in the brain was also manifest through the skull. In some ways he was correct – there is some degree of relationship between head size and overall intelligence (although this relationship is minimal – there is a better correlation between brain size and intelligence then head size and intelligence). Gall and his followers also incorrectly localized functions, including many personality traits, to various regions of the brain (skull). Another problem with phrenology is that Gall used mainly anecdotal evidence on which to found his theory. He also, instead of trying to disconfirm his theory, only paid attention to stories and evidence that supported his theory. While phrenology started out as legitimate in many ways, it quickly degenerated into little more than pop-psychology. Phrenology was discredited by the mid-1830s but it still had many followers throughout the 1800s.

One was phrenology was discredited was through the clinic method. Researchers like Paul Broca were able to show that damage in certain areas of the brain did produce specific deficits but that these deficits did not correspond with Gall’s theorized cranial areas. After many years of applying the clinical method to brain-behavior, the early tenets of Gall – those of brain localization and contralateral function (each hemisphere controls the opposite half of the body) – have been largely supported. Phrenology has not been supported.

Before Robert Whytt, little was known about human reflexes. Whytt was able to advance our knowledge through a series of experiments; he published the results in 1751. Previous scientists had noticed that decapitated animals (and people) still had muscle twitches. Whytt used decapitated animals to systematically show that he could make their muscles twitch by poking or pinching a leg. Clearly, basic reflexes did not require the brain. Whytt went beyond that though. He was able to dissociate reflex action from the brain by severing nerves between the spinal cord and an appendage. When the connection to the spinal cord was lost, there was no reflex. Whytt’s discoveries about reflexes went beyond simple automatic reflexes. He recognized that there was voluntary and involuntary action. The reflexes that he discovered the spinal cord played a large role in controlling were involuntary. He distinguished between voluntary and involuntary actions and stated that voluntary actions, if practiced enough, become habits. Habits, he stated, became more and more automatic with further practice. So while automatic and voluntary reflexes and actions are distinct they are not mutually exclusive. Whytt’s research was the forerunner to 20th century behaviorism, specifically classical conditioning.

A number of years after Whytt published his work, two independent researchers Sir Charles Bell and Francois Magendie discovered the functions of the two main nerve tracts in and out of the spinal cord. While Bell receives a lot of credit, Magendie’s work was the more scientific and documented – Bell just had a lot of political sway. What did these two researchers discover? Magendie exposed the spinal cord of a live dog and severed the posterior verve tract. The dog could still move its limbs but had no sensation in the affected area. Magendie was then able to sever the anterior root of a nerve tract. He discovered that the animal still had sensation in the affected area but no movement. He put the findings together and stated that the efferent anterior nerves controlled movement while the afferent posterior nerves controlled sensation. Bell had earlier discovered essentially the same thing. The law about the functioning of the nerve pathways became known as the Bell-Magendie law. Neurologists and neuropsychologists have been able to use this law as the basis for understanding different types of central nervous system injury.