Psychology is the study of mind and behavior. It is an academic discipline and an applied science which seeks to understand individuals and groups by establishing general principles and researching specific cases
Experimental psychology refers to work done by those who apply experimental methods to the study of behavior and the processes that underlie it. Experimental psychologists employ human participants and animal subjects to study a great many topics, including, among others sensation & perception, memory, cognition, learning, motivation, emotion; developmental processes, social psychology, and the neural substrates of all of these.[ The experimental approach in psychology has certain differences in comparison with the other sciences, which is probably caused by the peculiarity of the subject of investigation. In the most general view, psychology is considered as a science of “mind and behavior” and it studies the whole variety of aspects of human mental activity, including those that determine behavior. That is why, the lack of knowledge about the human mind is probably one of the reasons why the practice of experiment originated so late in psychology. Before they could start to bring actual results, the researches had to solve the following problems:
1. To develop adequate research methods for studying the mind as a substance neither being exposed to a direct observation nor interacting with any object of such kind.
2. To learn how to formulate the correct questions, which is crucial for experiments that are usually developed in order to answer some particular question, e.g. if some hypothesis is correct or not.
Starting with the first of these points, we may try to discover the common features of the human mental research methods. These features originate from the fact that it is still known so little about the subject. Of course, it is clear that the mental processing is carried out in the nervous system, which consists of the brain, spinal cord and the sympathetic nerves, but this kind of information has more value for neurophysiology then psychology. That’s why one of the common features of the experimental psychology methods is the necessity to consider the incertitude of the mind organizational principles, still being able to answer the particular research question concerning some aspects of its activity.
As the human mental activity takes a big variety of different forms, the “black box” system is adjusted to be capable to describe any kind of them. It is done through selecting different input/output systems, which supposes only the use of inputs/outputs carrying representational information and ignoring all other inputs/outputs. The famous reflex studies by I.P. Pavlov (carried on dogs because of the ethical principles) are considered to be one of the outstanding examples in experimental psychology (figure 4). These studies also constitute the “black-box” research, with the taste and audio receptors as inputs and the saliva secretion as the output. Of course, the usual types of psychological assessment on humans are much simpler then Pavlov’s experiments, they may not take clinical equipment or a long learning period to proceed.
A term “psychological test” is commonly used to refer to some kind of task, which a person is supposed to do in order to estimate his/her abilities, mental health or personal qualities. This may result in a possible equalization of notions of psychological test and assessment. However in the reality a psychological test actually represents a constituent part of assessment, which may also include such components like interview, demographic and medical profile, personal history, etc. These components may be represented on their own and/or may influence the results calculation of a test or a group of tests. This point of view is one of the basic believes in the experimental psychology, what can be seen expressed in the following definitions, shared by most experts in the field of psychological assessment.
Instruments used in experimental psychology evolved along with technical advances and with the shifting demands of experiments. The earliest instruments, such as the Hipp Chronoscope and the kymograph, were originally used for other purposes. The list below exemplifies some of the different instruments used over the years.
Hipp chronoscope / chronograph
This instrument, dating from around 1850, uses a vibrating reed to tick off time in 1000ths of a second. Originally designed for experiments in physics,it was later adapted to study the speed of bullets.[30] After then being introduced to physiology, it was finally used in psychology to measure reaction time and the duration of mental processes.
The first stereoscope was invented by Wheatstone in 1838.[31] It presents two slightly different images, one to each eye, at the same time. Typically the images are photographs of the same object taken from camera positions that mimic the position and separation of the eyes in the head. When one looks through the steroscope the photos fuse into a single image that conveys a powerful sense of depth and solidity.
Developed by Carl Ludwig in the 19th century, the kymograph is a revolving drum on which a moving stylus tracks the size of some measurement as a function of time. The kymograph is similar to the polygraph, which has a strip of paper moving under one or more pens. The kymograph was originally used to measure blood pressure and it later was used to measure muscle contractions and speech sounds. In psychology, it was often used to record response times.
This device is a photographic recorder. It used mirrors and light to record the photos. Inside a small box with a slit for light there are two drive rollers with film connecting the two. The light enters through the slit to record on the film. Some photokymographs have a lens so an appropriate speed for the film can be reached.
The galvanometer is an early instrument used to measure the strength of an electric current. Hermann von Helmholtz used it to detect the electrical signals generated by nerve impulses, and thus to measure the time taken by impulses to travel between two points on a nerve.
This apparatus was designed to produce several fixed frequencies at different levels of intensity. It could either deliver the tone to a subject’s ear or transmit sound oscillations to the skull. An experimenter would generally use an audiometer to find the auditory threshold of a subject. The data received from an audiometer is called an audiogram.
These determine the color composition by measuring its tricolor characteristics or matching of a color sample. This type of device would be used in visual experiments.[24]
Algesiometers and algometers
Both of these are mechanical stimulations of pain. They have a sharp needle-like stimulus point so it does not give the sensation of pressure. Experimenters use these when doing an experiment on analgesia.
An olfactometer is any device that is used to measure the sense of smell. The most basic type in early studies was placing a subject in a room containing a specific measured amount of an odorous substance. More intricate devices involve some form of sniffing device, such as the neck of a bottle. The most common olfactometer found in psychology laboratories at one point was the Zwaardemker olfactometer. It had two glass nasal tubes projecting through a screen. One end would be inserted into a stimulus chamber, the other end is inserted directly into the nostrils.
Probably one of the oldest instruments for studying memory would be the maze. The common goal is to get from point A to point B, however the mazes can vary in size and complexity. Two types of mazes commonly used with rats are the radial arm maze and the Morris water maze.[32] The radial arm maze consists of multiple arms radiating from a central point. Each arm has a small piece of food at the end. The Morris water maze is meant to test spatial learning. It uses a large round pool of water that is made opaque. The rat must swim around until it finds the escape platform that is hidden from view just below the surface of the water.
Electroencephalograph (EEG)
The EEG is an instrument that can reflect the summed electrical activity of neural cell assemblies in the brain. It was originally used as an attempt to improve medical diagnoses. Later it became a key instrument to psychologists in examining brain activity and it remains a key instrument used in the field today.
Functional magnetic resonance imaging (fMRI)
The fMRI is an instrument that can detect changes in blood oxygen levels over time. The increase in blood oxygen levels shows where brain activity occurs. These are rather bulky and expensive instruments which are generally found in hospitals. They are most commonly used for cognitive experiments.
Positron emission tomography (PET)
PET is also used to look at the brain. It can detect drugs binding neurotransmitter receptors in the brain. A down side to PET is that it requires radioisotopes to be injected into the body so the brain activity can be mapped out. The radioisotopes decay quickly so they do not accumulate in the body.

1.Pashler, H. (Ed)(2002) Stevens’ Handbook of Experimental Psychology; New York: Wiley
2.Khaleefa, Omar (1999). “Who Is the Founder of Psychophysics and Experimental Psychology?”. American Journal of Islamic Social Sciences 16: 2.
3.Hergenhahn, B.R. (2009) An Introduction to the History of Psychology. Cengage Learning.
4.Fraisse, P, Piaget, J, & Reuchlin, M. (1963). Experimental psychology: its scope and method. 1. History and method. New York: Basic Books.
5.Peirce, C.S.; Jastrow, J. (1885). “On Small Differences in Sensation”. Memoirs of the National Academy of Sciences 3: 73–83.
6.Hacking, Ian (September 1988). “Telepathy: Origins of Randomization in Experimental Design”. Isis 79 (A Special Issue on Artifact and Experiment): 427–51. doi:10.1086/354775. JSTOR 234674. MR 1013489.
7.Stigler, S.M. (November 1992). “A Historical View of Statistical Concepts in Psychology and Educational Research”. American Journal of Education 101 (1): 60–70. doi:10.1086/444032.
8.Trudy Dehue (December 1997). “Deception, Efficiency, and Random Groups: Psychology and the Gradual Origination of the Random Group Design”. Isis 88 (4): 653–73. doi:10.1086/383850. PMID 9519574.
Liszka, J.J. (1996). A General Introduction to the Semeiotic of C.S. Peirce. Indiana University Press.
Sowa, J.F. (1984). Conceptual structures: Information processing in mind and machine. Reading, MA: Addison-Wesley.


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