Vision Res.(10) Blackwell
Research into Visual Perception conducted by Blackwell
In 1959 Blackwell published details of an eight-year programme of research leading to the development of a general method by which optimum illumination levels for various practical tasks were determined.
In this work Blackwell described a series of experiments in which circular patches of light (stimuli) were presented to observers for a range of durations, the size and brightness of the stimuli also being varied systematically. On each presentation interval, during which a stimulus may or may not be shown, the observers were asked to indicate if they perceived a stimulus. Subsequent experiments of this type used rectangular and cross-shaped stimuli.
In 1960 Kincaid, Blackwell and Kristofferson presented a paper entitled ‘Neural Formulation of the Effects of Target Size and Shape upon Visual Detection’, in which they described a ‘quantitative general formulation for the effects of target size and shape upon visual detection, in terms of a hypothesized neural mechanism of human vision’.
In this paper they stated that:
“ The foundations of the present hypothesis were laid by Graham, Brown, and Mote in 1939. These authors suggested that the detectability of a symmetrical target of uniform luminance is determined by the amount of neural excitation produced at the centre of the neural representation of the target, the amount of excitation being maximal at the centre as a consequence of their assumption that every element of area within the target contributes excitation to the centre in proportion to a power function of the distance of the element from the centre.”
However, Graham et.al. confined their discussion to circles and although Kincaid et.al.’s title (Ref. 3., below) suggests that they investigated the effects of target shape upon visual detection, the account given is largely based on the results of experiments which employed only circular targets. It is possible that the resulting formulation may also apply to non-circular shapes, but no evidence was presented to indicate that hypothesis had been tested.
This section includes summaries of historial research and theories of human visual perception of simple two-dimensional objects. For more about the human visual system see The Eye, Parts of Eye, Eye & Vision Disorders, Ophthalmological Procedures.