Psychology has long moved away from the philosophy which considered the brain as separate from the body, and the era when psychology was studied from point of view of religion is over. was largely interested in the morality of humanity. Early attempts at empirical psychology, such as craniometry, which proposed a correlation between brain size and intelligence, and phrenology, which suggested that brain shape provides insight into a person's character, have also been abolished. due to lack of verifiable evidence (Hughes, 2012). . Yet one of the most popular fields of study in universities today is psychology. The 19th century saw a great spike in curiosity among scientists to understand the brain and human behavior. Factors such as the liberation of the university from authority also contributed to the efforts of professors to study their own intellectual interests and the evolutionary theory proposed by Charles Darwin led scientists to be more curious about humanity in terms of where we come from, where we are and where we are going. . These factors and perspectives have made psychology a science in its own right and continue to shape scientific research in psychology in 2018. Say no to plagiarism. Get a tailor-made essay on “Why Violent Video Games Should Not Be Banned”? Get the original essay In the 17th and 18th centuries, scientists like Galileo Galilei and Isaac Newton demonstrated that regularities observed in the universe are governed by laws which, in turn, can be explained by mathematical formulas. This gave observation an important role in science and led scientists to become more interested in human perception in the 19th century. One of these scientists was the German physician Ernst Heinrich Weber, who studied what ratio is necessary for a human being to discern the difference in weight when lifting two objects with a marginal difference in mass. This inspired his colleague Gustav Fechner to devise a law that numerically measured the degree to which a sensation was experienced by a human in relation to the strength of a stimulus (Brysbaert & Rastle 2013). Fechner also tested this theory on other human senses and, in doing so, refined the way he measured the barely perceptible difference. This became psychophysics: a method that measures the most primitive and intrinsic form of human perception known to all normally functioning humans (Read, 2015). This verifiable technique for observing human perception has its current uses, particularly when combined with technological advances such as functional magnetic resonance imaging or magnetoencephalography to expand knowledge of higher brain functioning (Read, 2015). Fechner's contemporary, Hermann von Helmholtz, also German, began to inquire about the speed of nerve impulses. To measure this, von Helmholtz stimulated a frog's motor nerve at different locations on its leg, using an electric shock, and precisely measured how long it took the muscle to contract. He conducted similar studies on humans but with a weaker electric shock and found a surprising consistency in their reaction times. However, von Helmholtz admitted that his results on humans depended entirely on the participant's attention span for the duration of the experiment (Schmidgen, 2002). This research motivated the Dutch professor of physiology, Franciscus Cornelius Donders, to reproduce the experiment, paying more attention tothe psychological aspect of the speed of communication between the human brain and the nervous system (Schmidgen 2002). Donders was disappointed by the galvanization of the participants and subsequently formulated his own test using human speech as both stimuli and reaction. In this test, Donders used a simple phonetic sound like "ki" and asked his participants to repeat it whenever they heard it. A second test was designed in which participants were presented with a succession of syllables (e.g. "ki", "ko", "ka") but participants were asked to respond only if they heard the word "ki" (Brysbaert and Rastle, 2013; Comparing the results of the two tests, Donders concluded that he had found the time necessary for a basic psychological process (Schmidgen, 2002). This method became the basis of Mental Chronometry: the valid procedure, still used today, for measuring the time required to perform a mental task (Brysbaert & Rastle 2013). In the 1800s, Charles Darwin discovered that plants with a particular trait can survive in certain terrain while others cannot. Plants with the trait that helps them survive in a specific territory then mate to form a new species. This process has been called natural selection (Brysbaert & Rastle, 2013) and is perhaps the most important scientific breakthrough of the 19th century. This hypothesis would encourage scientists to explore human evolution. Darwin's own cousin, Francis Galton, was inspired by this theory and believed that intelligence was passed down genetically to children from their parents. To prove his proposition, he designed and distributed a questionnaire to his fellow scientists to establish their personal backgrounds and intellectual influences. This was arguably the first time a questionnaire was used to investigate psychological factors (Fancher, 2009), an approach still popular among psychologists. From the questionnaire, Galton concluded that scientists' talent was innate, but their intellectual interest was enhanced and modified by other environmental factors. This is what coined the term “Nature vs Nature wish” which is still a hot topic of debate today. Galton also designed a similar questionnaire to study the behavioral characteristics of twins, but he realized that he could not really determine whether the similarities between the characteristics of a pair of twins were due to their genetics or whether the Differences in their characteristics were due to environmental influences (Fancher 2009). ). In addition to never finding truly conclusive evidence, Galton's work is influential in how intelligence and other psychological factors are currently measured. One of the most fundamental laws of the scientific method is that a scientist must be able to recreate an experiment and generate the same results. In the second half of the 19th century, Adolph Quetelet observed that this law is extremely difficult to follow when studying human behavior, because psychological measures are rooted in a large number of noises that can range from attention expenditure to biological differences between participants. He calls this accidental causes (Jahoda, 2015). To eliminate accidental causes, Quetelet examined many participants over a long period of time and calculated the average of the number of times a certain type of behavior could occur over the duration of observation (Brysbaert & Rastle, 2013). . Ronald Fisher refined this statistical method when he organized large amounts of data to see if conditions would be bestfor growing plants. Ultimately, Fisher proposed that it would be easier to divide the plants into a group where the soil was fertilized for a long time and a group where it was not, and then compare the average. Since all other confounding variables would also be averaged, the scientist can then see whether the fertilizer has an effect or not (Brysbaert & Rastle, 2013). This is the method that psychologists still use to test a null hypothesis (Write, 2009). According to Brysbaert & Rastle (2013), a large amount of psychological literature was already circulating in 1850. However, psychology was still not considered an independent discipline because it lent itself to theology and philosophy. All this would change in Germany, where universities stopped teaching religious dogma and professors were encouraged to pursue their own intellectual interests, giving Wilhelm Wundt the perfect opportunity to create the first psychology laboratory in Leipzig in 1879. Wundt defined psychology as the study of "mental consciousness" and therefore agreed to study consciousness empirically (Asthana, 2015). He actively encouraged research in psychology and inspired many young scientists to establish their own psychology laboratories and to teach psychology as an independent subject at universities around the world. Another contribution of Wundt was that he divided psychological processes into two distinct categories; simple psychological processes and complex psychological processes (Benjafield, 2002). He studied simple psychological processes such as sensation and perception using the experimental method and integrating psychophysical techniques, measurements of the duration of simple mental procedures and the precision of recall tasks. To investigate complex psychological processes such as language and the social aspect of human behavior, Wundt proposed the historical method in which he studied the differences between cultures and took into account social and historical aspects (Benjafield, 2002; Brysbaert and Rastle, 2013). The distinction between the use of experimental methods for simple psychological processes and historical methods for complex psychological processes is still visible in the way research is conducted by psychologists in the 21st century. Although Wilhelm Wundt inspired many scientists to study the mind's consciousness in the laboratory, it was a neurologist named Sigmund Freud who conceptualized an empirical method through which it became possible to better understand the unconscious thinking of people. men (Gedo, 2002), at the end of the 19th century (Moore, Meyer and Viljoen, 2015). Freud was interested in patients with hysterical symptoms and was convinced that these symptoms were caused by repressed memories from their childhood (Brysbaert & Rastle 2013). To understand his patients' unconscious thoughts, Freud asked his patients to remember their dreams. He used this method because he believed that patients' forbidden or repressed desires could pass through the barrier of consciousness during dreaming (Moore et al., 2015). After recalling their dream, sections of the dream are used as a stimulus to which patients must reveal the first words that come to mind without emotional bias, whether they think it is appropriate or not. From this practice, Freud can then interpret the dream and analyze the patient's unconscious thoughts. This method works because the unconscious cannot be discovered through introspection or conversation, as the patient only sees themselves through the perspective of their own biases (Moore et al., 2015). Grace.