The Use of Iambic Pentameter in the

In an extension of his 1984 study, Tullis (1996) set out to determine the specific
relationship between the number of groups and the average size (visual angle subtended)
of groups in user interface displays. Specifically, Tullis was interested in the group
number and visual angle range that optimized search speed. Tullis found that search time
is a function of the number of groups when groups contain visual angles measured at less
than 5 degrees. That is, for groups subtending a 5-degree visual angle, search time
increased with the number of groups. However, when the visual angle exceeds 5 degrees,
search time increased proportionally with visual angle.
Research by Tullis has assessed grouping interpretations and how fast users can
answer questions about grouped and ungrouped interface displays. However, other lines
of research have shown that grouping can affect users’ tasks with interface in more
indirect ways as well. As one example, Niemela and Saarinen (2000) used a visual search
task to study the effect of icon grouping on scanning speed. These researchers
hypothesized that the spatial grouping of icons of the same application type would
increase scanning speed.
To test this hypothesis, participants were presented with an icon-based user
interface, for an unlimited exposure duration, and asked to search for a target icon located
among four to sixteen distracter icons. In one condition, icons representing files that were
saved in the same application type were presented in proximal groups (see Figure 7A). In
a second condition, however, icons representing files saved in the same application type
were randomly displayed (see Figure 7B). Across 4, 8, and 16 item set sizes, Niemela
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