PsychoPhysical Methods

The Branch of Psychology which is concerned with the study of relationship between physical and psychological phenomenon is called Psycho-Physics.The Term Psycho-Physical method may be referred to all those methods in which attempts are made to employ physical devices for the scientific measurement of some psychological experiences like sensation of weight,brightness,loudness and others.

Psycho-logical Phenomena like sleep or span of memory ,can also be studied through the use of such psycho-physical methods.Three Classical psycho physical methods devised by the German physiologist and physicist Gustav Fechner (1801-1887).They are

1.The Method of minimal changes (or) methods of limits.
2.The Method of constant stimuli (or) the method of right and wrong responses.
3.The Method of average (or) mean error.

Method of Minimal Changes

The subject is exposed to experience a sensation.For Example,He may be asked whether he is able to see the object lying at a particular distance or not.If he says no then the value of the distance is gradually decreased until the subject reports that he is able to see it.In the next round,The object may be placed at the distance much nearer than the absolute threshold say 70cms in the present case.

All these values pertaining to minimal changes in the value of the absolute threshold (or) difference threshold in both decending and ascending series.

The Method of Constant Stimuli

In this method the value of the intensity of the sensory stimulus is neither gradually increased nor decreased in the case of the method of limits but the sensory stimuli of varying intensity are presented at random before the subject.

The Method of Average Error

This method is also called the method of mean error or the adjustment method.In performing experiment by this method,the subject is presented with some stimulus of the standard intensity.The avereage of the standard value for giving the subject's absolute threshold of sensitivity to the stimulus.