Experimental psychology refers to the branch of psychology concerning the basic process and design method of experimental research and its application in the field of basic research and practice of psychology.

Brief History

Before the nineteenth century, the problems of psychology were mostly discussed in the field of philosophy, using the method of speculation and empirical generalization. There was a prevailing belief that the experimental method was not applicable for the study of psychological phenomena. After the Renaissance, the materialist philosophical trend of ideas and the development of natural science in Europe gave birth to the experimental psychology at the end of the nineteenth century. The former includes John Locke’s materialist empiricism, David Hartley’s associationism, and Julien Offray de La Mettrie’s mechanical materialism. The latter includes the research on nerve conduction in physiology, the debate on brain function localization and the establishment of the theory of special energy of nerves, the evolution in biology, the atomism in chemistry, the discovery of personal equation in astronomy and the study on the reaction time caused by it, and the establishment of various laboratories in universities. Ernst Heinrich Weber determined the two-point threshold and the weight difference threshold in 1834, Gustav Theodor Fechner in 1860 put forward the psychophysical methods—the unique research method of psychology, in the book Elements of Psychophysics, and in 1875, William James established the psychology laboratory for demonstration in Harvard University. Be that as it may, since Wilhelm Wundt has been responsible for the organization and advocacy of laboratory experiments, people regard his establishment of the first research psychology laboratory at Leipzig University in Germany in 1879 as a sign of the separation of psychology from philosophy into an independent discipline, and hail Wundt as the founder of experimental psychology.

After the founding of the People’s Republic of China, the Chinese psychology community emphasized the transformation of psychology under the guidance of Marxist-Leninist philosophy, and extensively discussed the philosophical problems of psychology. Chinese psychologists realize that under the principle of guiding psychology by Marxist-Leninist philosophy, experimental research in psychology must be strengthened in order to further develop psychological theories and enable psychology to play its due role in socialist construction. With the development of education and science, universities and research institutions have established or expanded psychology laboratories, set up courses on experimental psychology, and actively carried out experimental research in psychology, thus the experimental psychology has been developed in China.

Research Contents

Classic experimental psychology research mainly includes the basic process of psychological experimental research, ethical issues of psychological research, the types of variables in psychological experimental research and the manipulation and control of variables, psychological experimental design methods, experimental methods and techniques (including traditional psychophysical methods, reaction time methods, modern methods and techniques of cognition and cognitive neuroscience), and the application of the aforementioned research methods and techniques in the fields of sensation, perception, consciousness and attention, memory, learning, acquisition of knowledge and skills, emotions and motivation, and other areas of basic and applied psychology. As the core branch of psychological research methods, experimental psychology is not only widely used in cognitive psychology, cognitive neuroscience, social psychology, developmental and educational psychology, and other basic research fields, but also extensively applied to engineering psychology, human ergonomics, human-machine-environment interaction based on network and information technology, and user interface design and other practical fields.

Experimental Methods

Wilhelm Wundt and Edward Bradford Titchener’s Experimental Method

The experimental methods used by Wundt and his student Titchener were inseparable from the psychological subjects they identified. They believe that psychology should study the direct experience of human beings, and that psychology seeks to decompose consciousness into its simplest and most basic elements. In order to achieve this goal, their psychological experiments are to analyze the contents of consciousness into psychological elements based on direct experience by introspective method under controlled conditions. They argue that a person can only be taken as a subject if he/she has undergone rigorous training. What the subject is trying to describe should be the state of consciousness caused by the stimulus and not the stimulus itself, otherwise he/she makes a “stimulus error”. They believe that all senses possess the following basic characteristics: quality, intensity, extensiveness, persistence, and clarity. In order to ensure clear experience and accurate report, experiments must be conducted, because the experiments are not only conducted under controlled conditions, but can be repeated. The more times the experiment is repeated, the clearer the experience becomes and the more accurately the experience is described. However, attempts to report changes in consciousness during the mental process will disrupt the state of consciousness at that time. In order to overcome this defect of introspective method, the method of recall is often adopted. Only subjects who have developed the habit of introspection can memorize or record their observations without disrupting their consciousness. Wundt also believes that the experimental method was suitable only for the study of basic mental processes, such as sensation and association. The higher psychological processes, such as memory, thought, social psychology, and personality, can only be explored through observation or the research on the history of human nature, for which Wundt wrote Folk Psychology.

Hermann Ebbinghaus and Oswald Külpe’s Experimental Method

Though experimental psychology began in Germany, not all the psychological experiments in Germany have been conducted in Wundt’s way. When Wundt pointed out that higher mental processes could not be studied experimentally, Hermann Ebbinghaus first investigated learning and memory problems through experimental methods. After having created nonsense syllables, he took the syllables as experimental materials, himself acted as the subject, and adopted the saving method to check the retention of different time intervals after memorization. This has not only expanded the research scope of experimental psychology, but also changed Wundt’s traditional psychological experiment method to analyze the content of consciousness. In addition, Wundt’s student Oswald Külpe was inspired by Ebbinghaus’s experimental study of memory and believed that thought processes could also be studied experimentally. However, he still followed the introspective method, though which was not the same as Wundt’s. He asked the subjects to complete a task and then reflect on the experience gained during the task. The subjects did not know in advance what they were to observe, only that they were to try to complete the assigned task. For instance, the subjects were asked to solve a problem, and to state how they thought step by step and how they solved the problem. Through experiments, he found that not all experience is composed of sensory images, and thinking can occur without any sensory or image content, thus he established the Würzburg school of image-free thinking.

Edward Lee Thorndike and Ivan Petrovich Pavlov’s Experimental Method

After the British biologist Charles Robert Darwin published his book The Expression of the Emotions in Man and Animals, although George John Romanes and C. Lloyd Morgan studied animal psychology, their observations were mostly conducted under natural conditions. It was Edward Lee Thorndike who conducted the study of animal learning under strictly controlled conditions. He developed the experimental method of connectionism and his early experiments were conducted in puzzle boxes with cats as subjects. He put hungry cats in a puzzle box made of slats and placed the food outside where the cats could see and smell it. In order to open the door of the puzzle box and eat the food, the cats must pull the right latch. At first the cats scratched until it happened to respond correctly and thus opened the door and ate the food. After many attempts, the wrong response gradually decreased, and the time required to open the door gradually shortened, until the correct response was instantly made as soon as the cats were placed in the puzzle box, and then, the learning was complete. This learning process of connecting responses to situations is known as Thorndike’s Law of Effect, which Thorndike calls as “Trial and Error Theory”, and is also called “trial and error” learning in psychology books.

Ivan Petrovich Pavlov’s experimental method of conditioned reflex and Edward Lee Thorndike’s method of trial-and-error learning were founded almost at the same time. A typical conditioned reflex experiment involves repeatedly pairing a stimulus (such as light) unrelated to a certain response (such as salivation) with a stimulus (such as food) that does elicit the response. If the animal salivates in response to light, the conditioned reflex is formed.

Both Thorndike and Pavlov developed experimental methods of animal learning that associated specific situations with specific responses. The difference is that in Pavlov’s experiment the situation associated with a response is presented by the experimenter, whereas in Thorndike’s experiment the situation was discovered by chance by the subject. The former can be said to be classical conditioning, while the latter is the precursor of tool or operation conditioning. Classical conditioning was thought to be limited to studying the reflexive responses controlled by the autonomic nervous system (e.g., salivary production), whereas instrumental conditioning was limited to studying voluntary responses associated with skeletal muscles (e.g., pressing on a crossbar, pulling back a door latch). However, Neal E. Miller et al. successfully trained subjects to control their own heart rate, intestinal contraction and diastole, and the α rhythm of brain electricity through feedback.

John Broadus Watson’s Experimental Method

John Broadus Watson considered psychology to be a branch of the natural sciences; psychology is not the study of consciousness, but of human and animal behavior; the purpose of the study of psychology is to predict behavior, find out the rules of behavior and control behavior. What he worked on in his lab was things that could be observed objectively. He did not require human subjects to observe their own conscious experience, but the experimenters to set experimental conditions and observe the response of the subjects under such conditions. He denied human instinct and believed that all actions were conditioned responses formed in society. Therefore, conditioned reflex method became the most important method for his psychological experiments. The traditional view is that the thought processes that take place in the mind are difficult to observe and experiment with. Watson, on the other hand, viewed thought as internal speech motor and observed the thought process by recording the movements of the larynx and tongue of the normal person and the movements of the hands and fingers of the deaf. Although he opposed the introspective method, he didn’t discard verbal reporting, believing that it was also an objective act. In short, his experimental method is to observe the responses of subjects under controlled conditions and to break down complex behaviors into “stimulus-response” units, which shows he didn’t get rid of the shackles of elementalism of structuralism school.

Experimental Method of Gestalt School

Based on the experimental research into apparent motion phenomenon, Max Wertheimer et.al proposed the view that perception is not the simple sum of sensory elements but a unified whole, which serves as the core of Gestalt Psychology. The concept of Gestalt applies not only to sensory experience, but also to learning, memory, thinking, and other processes. In brief, the whole is not determined by individual elements; while the parts are determined by the intrinsic properties of the whole. For instance, a tune composed of six notes can still be recognized as the tune itself after getting the six notes changed. That is to say, the recognition of the tune is not simply based on the six notes, but on the relations among different notes. As long as the relations remain unchanged, people can recognize the original tune. Thus, the experimental method of the Gestalt School is to find the structural principles of perception under the context set by the experimenter. For example, parts that are close in time or space tend to be perceived together. Problem-solving experiments are also to observe how subjects discover new relations between things under certain experimental conditions, such as how apes discover that two short bamboo poles could be connected to reach bananas outside the cage. The results of Gestalt experiments are often the descriptions of properties, rather than quantitative analysis.

Multi-factor Experimental Design

The use of methods of statistics in psychology began with Francis Galton’s work on individual differences. Later, Louis Leon Thurstone et al. developed the method of factor analysis. However, statistical methods have always been associated with psychological tests, which basically belong to the category of natural experiments and are not the same as the narrow experimental methods discussed here. The application of statistical methods to the design of psychological experiments is inseparable from the work of the British statistician Ronald Aylmer Fisher. Fisher developed the methods of analysis of variance and using small samples, and proposed the concept of null hypothesis and inferential statistics. His methods were first applied to the design of experiments in biology and agriculture, and later to the design of psychological experiments. Since then, the classical design method of controlling other factors and changing only one stimulus variable in psychological experiments has been pushed forward, and the multi-factor design method of changing several stimulus variables at the same time has been applied, which can help obtain the information about the interaction between various factors.

Development Trend

With the development of electronics and engineering technology, experimental devices and measuring instruments in psychology have become increasingly sophisticated, thus improving the objectivity and accuracy of experimental research in psychology, and gradually getting rid of the influence and shackles of different schools of psychology on experimental methods.

Through the cooperation with engineering, experimental psychology is applied to human-machine system, so that the designed machine can be more compliant with the structure and function of human body, so as to reduce labor intensity and improve work efficiency. Further application of mathematics in psychology allows for the creation of mathematical models after making quantitative assumptions about human behavior through experiments, such as mathematical models for learning based on probability theory, and mathematical theories of attention developed from experimental studies on disadvantaged children. The development of cybernetics and the widespread use of computers have not only enabled the data of psychological experiments to be processed in a very short time, but also facilitated the presentation of stimuli and recording responses by automatic control, discovered new ways to simulate complex mental processes, such as problem solving, further developed behavioral information processing theory and cognitive psychology, providing new interpretations for learning and memory, among other things.

With the progress of psychological research and the development of experimental psychology, as well as the needs of experimental research methods in basic and applied research fields, experimental psychology not only inherits the merits of traditional experimental design methods and technologies, but also absorbs methods and technologies of modern cognitive science and cognitive neuroscience. Its research methods are gradually diversified on the basis of traditional experimental methods so as to adapt to the research needs of various fields of applied psychology.