Anthropometrics: Important Aspects of Users’ Bodies - Foundations for Designing User-Centered Systems - page 56

Fig. 3.3 Easy to create modified gloves (they have wooden popsicle sticks in the fingers) and
goggles (with paint on them) that give the user restricted hand mobility and restricted vision
respectively
on existing knowledge—you learn to double click using a mouse button, for
example—but the most powerful and primitive affordances support direct inter-
action with the object. Norman's ( 1988 , 2013 ) book provides many examples of
useful affordances, as well as several that are confusing or even useless, such as
putting a pull handle on a door that you have to push open!
The objects in computer interfaces that can be manipulated (clicked, dragged,
rotated, and so on) by the user should also provide appropriate affordances. This is
why buttons, for example, should look like they need to be pressed (or clicked on)
even if they appear on a flat surface. Similarly, the use of a hand icon as a mouse
cursor in applications such as Adobe's Acrobat Reader is designed to afford the
action of scrolling through a document on the display.
3.2 Physical Aspects of Interaction
There are two main anthropometric issues that need to be considered when designing
interactive systems. The first relates to how the users will interact with the system:
will they be sitting (which is still most prevalent) or standing (which is becoming
more prevalent)? Note, however, that as computational artifacts are increasingly
embedded in our physical environment, the repertoire of possible body positions is
correspondingly increasing. The second, which is becoming increasingly important,
relates to how much weight the user can carry and support if the device or artifact is
intended to be carried by the user, as with mobile and portable devices.
3.2.1 Posture
The posture adopted by users when they interact with systems is important. If users
adopt an incorrect posture or stay still too long, this can lead to performance