What operations
are used to identify the characters in a visual display,
and how are these operations arranged in time? These questions
have attracted experimental psychologists since their field
began, and different answers have been offered, based on
the data from various paradigms. To investigate these issues,
we used a task in which subjects under time pressure had
to recite the names of all the items (numerals) in a briefly-presented
visual array. We manipulated the number of items in the
array and their legibilities.
We found that
degrading one or more items produces dramatically different
timing patterns, depending on type of degradation. Superimposition
of a grid influences primarily a parallel component (alpha;
contour formation?) of the encoding process, whereas disorientation
influences primarily a serial component (gamma; memory interrogation?).
Data patterns that result when the two forms of degradation
are combined within and across items also require us to
postulate a third component (beta; feature extraction?)
that occurs between the alpha and gamma components. The
betas for different items occur serially, probably in the
same order as the reciting order. Within an item, alpha,
beta, and gamma appear to be arranged in series. Across
items, alpha and beta can overlap: The beta operation for
one item can start before the alpha operations for other
items have been completed. This overlap property permits
the parallel alpha process to reveal the seriality of the
beta process.
