This is a branch of psychology in which experimental techniques are utilized to obtain reliable data. It is a method of studying psychological problems; the term connotes all areas of psychology which use the experimental method. In a narrow sense, the definition suggests the use of a laboratory although all psychological events are not observed in a lab. One such method includes public opinion polls which consists of data that has been compiled outside a laboratory. Therefore the laboratory becomes a computing room. In a broader sense, all psychology is experimental because all psychologists think and work in terms of quantitative data.
The experimental method as it applies to psychology is an attempt to account for the activities and behaviors of living and nonliving systems by manipulable relationships. Areas of study that rely heavily on the experimental method include those of sensory and perception, learning and memory, motivation and physiological psychology. Some of the branches are child psychology, clinical psychology, educational psychology, social psychology and even parapsychology. The experimental psychologist often concludes this his problems overlap those of physiology, neurophysiology, radiology, biochemistry, zoology, geneticists and physics. Normally, the experimental psychologist works with normal, intact organisms but in physiological psychology, studies are performed on organisms modified by brain or nervous system surgery, radiation, drug treatment, induced convulsion, or long-standing deprivation of normal physiological function.
Image Credit: C.H. Stoelting Co.
Whipple's mirror-drawing apparatus is used in experimental psychology which aimed to determine the level of motor-coordination between hand and the eye. The test subject can only view the illustration in the mirror. The shield obscures seeing the hand's movement. The subject draws what he sees and the pencil pressure and markings provide a fair test of his co-ordination.
The first laboratory for psychological research was established in 1879 in Leipzig, Germany by Wilhelm Max Wundt, the culmination of the efforts of physiologists and physicists fascinated by the functions of the sensory organs.
Laboratory research in psychology had its start as a descriptive science focused primarily on an analysis of consciousness in the sensory components and the experimental procedure co-ordinated several expert disciplines. For instance, if light and color was to be researched, the physicist analyzed it as properties of wave lengths, amplitude and composition of electromagnetic waves. Psychologists determined which aspects of consciousness relied on these isolated physical attributes; the physiologist's goal was to ascertain the physical and psychological analysis of color to specific eye structure.
The psychological search for analysis of mental experience under the condition of rigid stimulus, which became known as experimental introspection, or a method of observing an individual's mental contents in a prescribed manner.
It was not enough to simply describe the mental contents and construct systems of classification, because a science that aims to fulfill itself cannot stay at a descriptive level forever.
The next step goal for the psychologists was to make a determination of the amount of sensation present in awareness. Well before the formal opening of the laboratory, Gustav Theodor Fechner, a physiologist-philosopher, had considered the matter of measuring sensation, noting the results of E.H. Weber, a German physiologist who had performed studies on sensory discrimination in weight lifting, finding that any weight, the barely perceptible difference in weight is a certain fraction of the weight, a fraction that is a constant holding for a fairly wide range of weights. Weber's fraction is demonstrated with brightness discrimination where if 1 candle were added to 100 candles to produce a hardly noticeable difference in brightness, then 5 candles must be added to 500 to similarly produce a hardly noticeable brightness in the over-all quantity.
Fechner believed there were very important implications in Weber's observations and generalized Weber's fraction into a law that is related to physical dimensions with psychological dimensions.The Weber-Fechner law states if physical stimuli are increased geometrically, the attending sensations will increase arithmetically. The result being, knowledge of physical quantities provides a basis for prediction of sensory quantities and vice versa. Fechner's experiments gave rise to psychologists developing interest in development of psychological scales that are measured in units. It is possible to make fractions of sensation; such as a sound of certain volume can be divided into different measurements, such as a quarter or half of the original volume. Fecher published Elemente der Psychophysik in 1860 in which various techniques of measuring psychological events were documented in great detail. These techniques were proven to form the basis of measurement in all fields of psychology, many professionals in the field date the establishment of experimental psychology to the publication of Fechner's book.
In 1885, Hermann Ebbinghaus was successful at application of quantitative techniques in research on memory. He used nonsensical syllables, and meaningless words which were formed by insertion of a vowel between two consonants like tif, vux and jep. Such syllable gibberish ruled out any established associations. Ebbinghaus developed alternative techniques to measure memory. The saving method requires the subject to memorize a series of nonsensical syllables to the point at which he is just able to repeat them. The number of trials, to just barely remember the series is noted in his research. For instance, 20 trials were necessary, which were followed by an interval of only 15 trials to relearn the same series, which saves five trials, or 25%. Ebbinghaus made a determination on the curve of forgetting as well as measuring the efficiency of certain learning techniques in regard to the quantity of material retained in memory. His research was of profound interest to educators in the field of psychology.
Contributions of Ebbinghaus signaled a turning point in experimental psychology, opening the way to study mental processes which are more complex than simple sensory and motor phenomena. Psychology began to shift its focus from introspection to measures of performance and behavior. Many practical psychologists arose such as educational, child and legal. The shift was away from individual introspective analysis and toward group and individual behavior. With the refocusing, came a parallel shift in theory. The individual was approached from a functional perspective, stressing the adjustment of the organism to its environment. From this approach, the mind was a special organ of adjustment, and less interest as a state of consciousness, a point of view which is known as functional psychology.
Studies of animals reveal many important psychological phenomena which were addressed only mildly through the introspective approach. Deprivation of basic necessities such as food and water, lead to increased behavior patterns which were observed. Isolating biological drives and needs, signaled an emergence of the psychology of motivation.
Early accomplishments of experimental psychology was in establishing techniques that established psychological facts; interest shifted to a more deductive experimental design. One controversy in experimental psychology that has remained undecided is in answering how animals learn. The opposed hypotheses are the stimulus-response approach that declares all learning is made possible by mechanical connecting of stimulus and response, and the cognitive approach, states that learning is a result of acquired knowledge about the environment. The research instigated an experiment using rats in a maze situation. Many corollaries of both hypotheses were tested, the main focus, which is how animals learn remains undecided.
See Conditioned Response, Learning, Stimulus.