Ergonomics - iPhone Game Blueprints - page 58

finger, so its width is at least 25 mm; it helps to demonstrate the visual feedback
of the control element, and the finger does not cover the image. In case the player
doesn't notice the feedback or other forms of results on the screen, he is convinced
that the input doesn't work and tries to tap again and again, which can cause an
accumulation of wrong inputs. Any button is perceived perfectly if it has some an-
imation between states rather than a static frame, for each mode. For example,on
being pressed it can demonstrate a smooth dent effect. Otherwise, a button can be
increased in size and, in parallel, its alpha can be reduced to zero, since it becomes
bigger and smoothly disappears. Such animation fixates an image of a used control,
a user is sure that the button was really pressed.
In 1995, Louise Banton published the article The Role of Visual and Auditory Feed-
back during the Sight-Reading of Music in Psychology of Music and Music Educa-
tion , where a very interesting study was described. A number of pianists were tested,
theywereaskedtoperformsight-reading.Someofthemplayedinnormalconditions,
while others had some restrictions: the first group was unable to hear the music they
were playing (no auditory feedback), the second group was unable to see the piano
keyboard (no visual feedback). Amazingly, the results showed that those musicians
who played in normal conditions and those who had no auditory feedback made sig-
nificantly lesser errors than the musicians who had no visual feedback. Moreover,
the playing in normal conditions and the playing without auditory feedback were very
close to one another in the error count. So, visual feedback is very important to re-
duce the level of inputting errors.
Auditory feedback is important too, especially for small control elements, because a
finger covers the visual part of a button. Thus, a sound effect can convince the player
that the input works properly. Various click-and-beep sounds can be utilized, ideally
if they match the mood of the game. According to the dissertation by Gregory T.
Bender , Touch Screen Performance as a Function of the Duration of Auditory Feed-
back and Target Size , auditory feedback between 50 and 400 ms should be used for
small buttons, and such continuity can reduce the level of errors. Additionally, there
is a relation between the time the user holds his finger on the screen and the dura-
tion of the auditory feedback. In other words, people keep their fingers pressed down
till a button's sound effect stops. He writes, "Additionally, avoiding auditory feedback
longer than 100 ms may also minimize contact time with the touch screen."