2.gif)
The text column display (Figure 3) again used numbers for group labels, but instead of having these groups organized across the display array, the text column display formed columns of groups. The display arrays in this condition were side by side, and so the directional cues in the target display indicated whether the goal was located in the left or right array.
Figure 3:
The Text Column Display. The black arrow in the target
display indicated that the goal item was located in the right array.
3.gif)
Unlike the text row and text column displays, the text block display in Figure 4 did not display groups in stripes across the array, but instead used blocks of similarly numbered items. These blocks were 4 items per side, and therefore contained the same number of items as the previous displays. In the text block condition, like the text row condition, the two display arrays were stacked vertically, and the directional cue indicated whether the goal was in the top or bottom array.
Figure 4:
The Text Block Display. The black arrow in the target
display indicated that the goal item was located in the bottom array.
4.gif)
The color row condition (Figure 5) was an analog to the text row condition but instead of using a text cue (numbers) to delineate groups, one of eight distinguishable colors were the grouping factors. The colors were red, green, blue, purple, brown, pink, yellow and orange, chosen becuase of their excellent descriminability. In this condition, the 7mm box was filled with one of these solid colors, with letters printed in black within the box. The luminance differences between the black text and the colored background was approximately the same as the text rows displays contrast in an attempt to eliminate the possible effects of text legibility on performance.
Figure 5:
The Color Row Display. The bands of colored blocks indicated the same grouping that the number
grouping cue did in the text row display.
5.gif)
A similar analogy existed between the color column and text column displays (Figure 6). In this condition, colors were used to indicate column groups, while letters indicated row groups.
Figure 6:
The Color Column Display. An analog to the text column display substituted chromatic grouping cues for
numeric grouping cues.
6.gif)
Finally, the color block display (Figure 7) uses the same block organization as the text block display, but used the chromatic grouping cue found in the other color designs instead of the number blocking cue found in the text block condition. Members of a group shared the same color, and items within that group were labeled with letters.
Figure 7:
The Color Block Display. Clearly delineated grouping blocks containing alphabetically ordered items
shown left-to-right, with left-to-right wrapping.
7.gif)
Selection was accomplished with either an Apple Macintosh(TM) Mouse or a Summagraphics(TM) Summa Sketch II graphics tablet shown in Figure 8.
Figure 8:
The Summagraphics(TM) Summa Sketch II graphics tablet
with one of the 6 templates used for selection.
8.gif)
The mouse was set to twice the maximum gain allowed by the Macintosh(TM) control panel using the Mouse II control panel. The specific gain used was fairly unimportant in performance (Kantowitz & Elvers, 1988) but gain was accelerated to prevent the necessity of "walking" or repositioning the mouse during selections. This served to eliminate some of the variability found in mouse selection. The graphics tablet was set in tablet mode with a template that matches the screen layout. The template was changed to match the six screen designs. The templates match the size of the display on screen with the screen mapped directly to points on the tablet. Selection on the graphics pad was accomplished by pointing to the target with an electronic stylus and pressing down. This activated a micro-switch in the tip of the stylus. In both selection methods, selections were acknowledged by a simple beep from the computer.
Procedure
The mouse location was then adjusted according to their handedness. Due
to some hardware problems, the first 2/3 of the subjects were assigned to the
mouse input condition and the last 1/3 to the tablet input condition. Printed
instructions were used to familiarize subjects with the task. These
instructions are found in Appendix B. All subjects were instructed in the
proper use of the input device using a paper instruction manual. they were
guided through their first selection by the experimenter. Subjects were shown
the target and then the goal but no cues about organization or strategy were
given. Subjects were informed that their speed to select the target was being
timed and were instructed to proceed as quickly as possible without making too
many errors. Error trials were recorded with subjects continuing until they
completed 64 error free trials. The order of display type presentation was
assigned using a latin squares design so that each display type appeared in
each order position at the same frequency, controlling for order effects. Four
test targets were selected randomly from each 16 X 16 block of goal boxes with
the order of these blocks chosen randomly to assure that goal items appeared in
all areas of the display equally.
Trials began with the selection of the green "show target" trigger. Selection of this trigger revealed the trial target area. This window shows the target and the directional cue showing which array the goal would be found. Subjects were timed by the computer with a 1/60 second(+/- 3/60) accuracy beginning at the appearance of the trial target area and ending with the selection of any area outside of the trigger box. Selection of improper targets was noted, as well as missed targets. Rest periods could be taken at any time during the experiment.