Psychology

Background information
The theory of object constancy is directly related to the phenomena of the Stroop Effect which is a psychological process where objects are perceived in a more or less standard way despite the difference in the sizes of the object. With respect to size constancy, the perceived size of an object an individual is familiar with usually remained unchanged despite the doubling of retinal images with the halving of the distance between the viewer and the object. (Kolers). Constancy also plays a role in cases where the orientation of a give object can affected the perception of the orientation of another object (Gilinsky, 1967)

From a psychological point of view, the stroop effect can be defined as an illustration of a tasks reaction time. A simple example is the case when name of specific colors are printed in colors that do not denote the name for instance the word green can be printed in purple ink as opposed to green ink, it takes longer for an individual to name the color and he is likely err than in cases when the colors resemble.

This phenomenon was named in the honor of John Stroop the first psychologist to phenomenon in English. Stroops findings were based on earlier works of a psychologist known James Cattell who made interesting observation in the early 90s. Cattell measured the response time needed to measure various stimuli and made a fundamental observation  that it took more time to name objects like horses than it took to read corresponding words (Cattel,1886). His explanation that reading is a much learned trait introduced a new theory in the world of psychology the theory of automaticity which has remained highly influential and even directly influenced the work of Stroop. The publication was done in English in 1935. The publication has since been the most widely cited publication in experimental psychology.  The effect has been successfully used to design psychological tests that are now being used in clinical observation and investigation worldwide.

During the experiments, Stroop gave variants of the test during which 3 stimuli were employed. The first variant saw the names written in black ink. While the second variant saw the colors name written in inks that differed from the colors name. And in the final one the colors were the square of each given color.

He used two stimuli in experiment 1. This required each participant to read the names color regardless of the inks color. During experiment 2, another two set of stimuli were used. Each participant had to speak out colors of each letter regardless of the words written with stimulus 2. Finally they had to name the colors of the individual dot squares. For example when the word pink was in blue, they had to say blue, and not pink whenever each square was shown, they had to speak out the color. During Stroops last experiment, the participants were tested on the different stages of doing each task. He took note of the increase in time take to name the colors. These delays did not appear in the experiment 1. These interferences were owed to automation of the reading process, in the subconscious is responsible for determination of the meanings of words (on reading blue the mind thinks of the blue color). The mechanism by which constancy is achieved has not been explained or understood well

Since the works of Stroop and Cattell many review articles and experiments have been carried out to try explaining the phenomena of constancy. These reviews were based on flaws in Stroops experiment. For instance Jensen (1965) addressed the issue of timing of responses by participants in cognitive tests, he introduces the idea of score cards with respect to Stroops experiment As opposed to many researchers now performing the Stroop test used in psychological examination, Stroop did not compare the time taken to read the black words or the time that was needed to name the colors that were not concurring with words written.

Stroop experiment has generated a lot of interest over the years and various variants of the experiments have since been made. The most common procedure used today has remained similar to the second experiment Stroop carried out in 1935 which involved reading names written in  the color black against different colors has attracted little interest. The scores in both cases normally referred to as interference scores are usually measured with respect to the difference in time needed to read each type of card. A list of stimulus is still in use with improved control of variables as opposed to the lack of control that Stroop had. The different characteristics of the stimuli such as direction of words or ink colors have been systematically varied. Despite all this changes interference has not been changed and remarkable results are always found.

Presently cognitive psychologists have switched to conducting most of their experiments over computer control. The colored rectangular controls used by Stroop have now been successfully been replaced by keyboard characters.