Spatial Ability and Information Shape:
		When Do Individual Differences Matter?

James Blustein and Jason Satel

   Psychologists have long known that cognitive differences between
individuals can significantly affect performance on a variety of tasks.
Several recent studies have shown that so-called spatial reasoning ability
has a significant effect on users success with (spatial and non-spatial)
hypertexts. If we understood why spatial ability has such a strong effect
on success with hypertext then we could adapt hypertext for use by
different types of people, and explore new types of presentation.

   It is clear that the different success rates are not solely due to the
hypertext systems and the need to integrate two-dimensional spatial data
(as with spatial HT systems like VKB) but rather the need to make sense of,
and navigate in, multi-dimensional structures of meaning.  A. Dillon and
D. Schaap refer to some of these issues as `information shape'.

   Despite clear evidence that spatial reasoning ability affects success
with hypertext, studies of the effect are remarkably vague about what
subfactors were assessed.  We have made a preliminary analysis of these
studies to determine their common components.  We present both a survey of
studies of hypertext that have found such effects, and an investigation
into the underlying causes.