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to relate the detectability of certain local structure to the detection thresholds
of isolated simple shapes. In this chapter we shall consider some of the various
laboratory experiments which have been carried out to attempt to determine the
thresholds associated with a variety of recognition tasks. The coverage can be by
no means comprehensive owing to the enormous field covered by the term
recognition. Rather we shall only summarise general statements and present
some of the more clear cut threshold behavioural trends. The reader wishing to
pursue this particular facet of acquisition in depth is recommended to start with
Yves le Grand’s book ‘Form and Space Vision’ for general reading or Zusne’s
book ‘Perception of Form’ for a study in depth. The latter reference itself
contains some 2 500 references to information related to recognition - an
indication of the scope of the subject.
Before proceeding to a study of various forms of recognition it is necessary to
discuss a few general points about the subject of recognition. Firstly, whilst
detection may be considered as a decision that a local difference in energy exists,
recognition can by no means be treated so simply. Ability to recognise must
depend, at least to some extent, on such factors as the number of possible
stimuli, complexity of form, previous experience of particular forms, orientation
of retinal image and association with the particular field of view in addition to
the factors found to influence detection. Since the many psychological facets of
recognition are beyond the scope of this book we shall in general restrict
ourselves to a study of the physical aspects of recognition. However, it is
impossible to separate the physical and psychological factors into watertight
compartments, so some background of interactions between physical and
psychological is important for the reader.
The site of the main recognition processes is variously assumed to be at the
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