Gestalt psychology

Max Wertheimer's experimental studies of seen movement appeared in the Zeitschrift für Psychologie, published in Leipzig in 1912. The paper came from the psychological institute in Frankfurt.

The experiments were carried out in the autumn and winter of 1910 at the Frankfurt institute. Wertheimer used Friedrich Schumann's tachistoscope, an instrument that shows images for brief, controlled times.

Wertheimer showed that people see motion in rapidly flickering static images. The insight came to him while he used a child's toy tachistoscope.

His assistants Wolfgang Köhler and Kurt Koffka later became his partners. They believed perception involves more than adding up sensory stimuli, and that belief became a movement in psychology called Gestalt psychology.

The German word gestalt means form or pattern. The movement's central idea is that the whole differs from the sum of its parts, so the brain builds a perception that is more than the available sensory inputs, and does so in predictable ways.

Wertheimer published his grouping laws in 1923 as the second of his studies on the theory of the Gestalt, in Psychologische Forschung, volume 4, pages 301 to 350.

He argued that when we see a number of stimuli we do not usually experience a number of separate things. We experience larger wholes set apart from one another, and a row of scattered dots is seen as figures rather than as a sum of dots.

Dots usually combine in a spontaneous, natural grouping. Any other arrangement can be achieved but is artificial and hard to hold for long.

In a row of equally coloured dots, the most natural grouping is the one with the smallest interval between dots. Wertheimer named this the factor of proximity and called it the first of the principles he set out to find.

Adding dots does not weaken the natural grouping. With a long row of dots, the pairing is never abandoned and individual points seen instead. Only the unnatural, artificial grouping becomes harder as dots are added.

Reading gives a daily example of proximity. Letters are grouped into words because there are no spaces between letters, and words are separated because there are spaces between them.

With the spacing kept equal and only the colour of the dots changed, dots of the same colour group together. Wertheimer called this the factor of similarity.

Similarity and proximity can oppose each other. Wertheimer showed an arrangement in which similarity wins against proximity, and another in which its victory is less decided.

The principles apply to hearing as well as sight. Beats that alternate soft and loud at constant intervals are heard in natural groups, and trying to hear another arrangement cannot be kept up for long.

The factor of closure says that if four points make two self-enclosed units, that grouping is apprehended in preference to the alternative. Wertheimer added that closure is not always the dominant factor, and that in one of his figures the factor of the good curve predominates instead.

Another principle, common fate, is shown by shifting some dots in a row. A shift of a whole naturally related group looks smooth, while a shift that splits a natural group looks far less so.

Wertheimer also listed past experience, or habit, as a separate factor. If A and B have become habitually associated but B and C have not, ABC tends to appear as AB and C.

The law of continuity says we are more likely to see smooth flowing lines than jagged, broken ones, and the principle of closure says we organize perceptions into complete objects rather than series of parts.

Another Gestalt principle is figure and ground: we split the visual world into a figure that is the focus and a background behind it. A football fan, for instance, groups players by the colours of their uniforms, which is similarity at work.