Masaaki Kurosu and Kaori Kashimura
Design Center, Hitachi Ltd.
5-2-1 Minami-aoyama, Minato-ku, Tokyo 107 JAPAN
+81-3-5485-1451
PFD00343@niftyserve.or.jp
kasimura@crl.hitachi.co.jp
Twenty-six subjects, including 9 GUI designers, 6 industrial designers, 8 engineers and 3 secretaries,
participated in the experiment and were asked to locate those elements on the computer screen as they might
think optimal in various senses. The hard copies of the screen were used as stimuli in the evaluation
research.
FIGURE 1No caption provided
Fig. 1 shows the configuration of 26 layout samples on the plane with the beauty (abscissa) and the apparent
usability (ordinate). Relatively high correlation (0.589) was obtained between these two scales which
suggests that the apparent usability is somewhat related to the aesthetic aspect of the layout pattern. Four
typical sample layouts are shown in Fig. 2. The upper right sample was rated highly usable and highly
beautiful, and the lower left sample was rated less usable and less beautiful.
FIGURE 2No caption provided
From the interview with the interface designers, following strategies were discovered to be or, at least,
seemed to be effective in the actual design process. The list also shows the measurement methods adopted
in the analysis (in parenthesis).
(1.1)_ Glance sequence
The main display should be placed at the upper left corner, because the user may start to look at the screen
from there then may go down right. Because the main display is showing information that is necessary for
the subsequent operation, it should be seen by the user first in the total operation sequence. (The distance
between the center of the main display and the top left corner of the screen in cm.)
(1.2) Familiarity
The numeric keys should be arranged as on the telephone keypad (1 2 3 keys at the top row) rather than the
keys on the calculator (7 8 9 keys at the top row), because the former has more familiarity for the ordinary
user. The horizontal alignmen is not recommended because of the inefficiency of the hand motion and the
possible existence of the parallax caused by the thick glass cover. (Type of the key pattern.
(1.3) Grouping
Keys should be grouped according to their functions. This is based on the concept of the perceptual
grouping of the Gestalt psychology. (Number of key groups.)
(2.1) Operation sequence - 1
Special numeric keys should be arranged from higher value keys to lower ones, based on the consideration
of the order of operation. (Type of sequence.
(2.2) Hand dominance
Numeric keys should be placed on the right hand side of the screen. (The distance between the center of the
key 5 and the right edge of the screen in cm.)
(2.3) Operation sequence - 2
The Yen key should be placed at the lower right corner of the screen. (The distance between the center of
the Yen key and the lower right corner of the screen in cm.)
(3) Safety strategy
The cancel key should be placed far apart from the main key block to avoid a mistouch. (The distance
between the center of the cancel key and the center of the key 5 in cm.)
Correlation coefficients and coefficients of contingency (for the nominal scale) were calculated for each
strategy measures of the ineherent usability with the rating value of the apparent usability. Values obtained
were unexpectedly low in many cases as follows.
Introduction
Interface designers are making efforts to increase the efficiency of the operation, to make the interface easy
to understand, and to increase the safety of data from mis-operations. But such efforts are hard to evaluate
unless the user actually uses it. That is to say, such inherent usability is meaningless for the user if the
product is not appealing enough for them to buy it. This is the reason why we started to study the
determinants of the apparent usability. We think that the products should be apparently usable as well as
inherently usable.
1. GENERATION OF LAYOUT PATTERNS
From among various aspects of the graphical interface design, we selected the screen layout for the study of
apparent usability. As a first step, we had to collect variations of the layout pattern. Our methodology was
to let the subjects generate their own layout using the same graphical elements. The sample screen was
taken from a cash dispenser which had ten numeric keys, special numeric keys (thousands and ten-
thousands), the Yen key (as a delimiter), the cancel key, the correction key, the main display and the sub
display (the figure of a lady) as graphical elements.
2. EVALUATION RESEARCH
Twenty-six layout patterns were then evaluated in both the functional aspect and the aesthetic aspect. A
total of 252 subjects were asked to rate these two aspects on the ten point rating scales, i.e. how easy to use
they looked (apparently usable) and how beautiful they looked. The subjets included 156 students of a
design school and 96 students of a psychology course of a university. Because both groups of subjects
showed high correlations in their judgments (0.679 for the apparent usability and 0.783 for the beauty), we
merged the data to use in the analysis that followed.
3. DETERMINANTS OF APPARENT USABILITY
What we did next was to discover principal determinants of the apparent usability. For the determinants, we
listed factors that interface designers believe to enhance the inherent usability.
(1) Cognitive efficiency strategies
(2) Operational efficiency strategies
(1.1) Glance sequence ............... 0.000
(1.2) Familiarity ..................... 0.730
(1.3) Grouping ........................ 0.075
(2.1) Operation sequence 1 ......... 0.113
(2.2) Hand dominance ............... -0.127
(2.3) Operation sequence 2 ......... -0.306
(3) Safety strategy ................... 0.137
CONCLUSION
These results show that the apparent usability is less correlated with the inherent usability compared to the
apparent beauty which showed the correlation coefficient of 0.589. This suggests that the user may be
strongly affected by the aesthetic aspect of the interface even when they try to evaluate the interface in its
functional aspects and it is suggested that the interface designers should strive not only to improve the
inherent usability but also brush up the apparent usability or the aesthetic aspect of the interface. Out next
study will focus on the determinants of the aesthetic evaluation of the interface.
