Research into Visual Perception conducted by Braly
From the mid-1920s to the early 1940s the influence of past experience
on human visual perception was a popular research area. Many investigators
employed arrangements of simple two-dimensional geometrical shapes,
sometimes alone and sometimes embedded in more complex forms.
Braly considered that Gottschaldt’s
results related more to the recognition of visual units (determined
by lines, contours and spatial relations),
than to the effect of past experience on perception.
Braly conducted experiments
to determine ‘the influence
of the perception of certain visual forms upon the subsequent perception
of other visual forms’. These involved presenting simple geometrical
forms incl. triangles, quadrilaterals and pentagons to observers.
These figures were represented by arrangements
of dots because the perception of groups of dots for any given figure
to depend more upon subjective, attitudinal factors, influenced by past experience,
than was the perception of outlined figures.
The first nine slides for each
experiment comprised the impression-series, and the last nine (or eleven)
slides comprised the test series. In each of
the first five experiments 20 observers were given the impression-
and 20 observers were given only the test-series. Each slide was displayed
for approximately 0.175 seconds, after which observers were asked to
draw the figure
or figures whose corners were represented by the dots in their relative positions.
Only if the dots could not readily be seen as indicating a particular figure,
were the observers asked to draw the dots (rather than the figures) also in
the positions in which they appeared.
The experimental results indicated that ‘the perception of visual stimuli
may be significantly modified by past experience resulting from the previous
perception of other visual stimuli’ (the modification may take the form
of changes of the form of figures perceived, or as additions of new figures
in the total perception).
Braly’s results were in complete disagreement with Gottschaldt’s
and increased debate. Subsequent
investigators largely discontinued the use of the simple geometric
forms and their results generally opposed Gottschaldt’s conclusion
that past experience was of little consequence, or at least had a lesser
effect on perception
than that due to the nature of the ‘whole’ objects viewed.