Touch and Speech: Multimodal Interaction for Elderly Persons - Biomedical Engineering Systems and Technologies - page 362

objects are either causing too much distraction, or becoming less noticeable. To cope
with these impairments, the following guidelines should be taken into account:

• Layouts of the user interface should be devised as simple and clear as possible,

with few (if any) or no overlapping items.
•

All texts should be large enough to be readable on the communicating interfaces.

• Strong contrast should be used with as few colors as possible; this also applies to

simple and easily recognizable shape designs.
•

Unnecessary and irrelevant visual effects should be avoided.

2.2 Speech Ability

Elderly persons need more time to produce complex words or longer sentences, prob-
ably due to reduced motor control of tongue and lips (cf. [8]). Furthermore, speech-
related adaptation is necessary to improve the interaction quality to a sufficient level
(cf. [9]). Based on these, the following aspects should be taken into account:

• Special acoustic models for the elderly should be used for speech recognizer.

• Vocabulary should be built with more definite articles, auxiliaries, first person

pronouns and lexical items related to social interaction. Texts should be as simple as
possible.
• Dialogue strategies should be able to cope with elderly specific needs such as re-

peating, helping and social interaction, etc.

2.3 Auditory Perception

Hearing ability declines at least to 75% after 75 year olds (cf. [10]). High pitched
sounds are increasingly lost, as well as long and complex sentences becoming diffi-
cult to follow (cf. [11]). Therefore special attention should be paid to the following:

• Text displays can help when information is mis- or not heard, which should not

provide conflicting information.
• Synthesized texts should be intensively revised regarding style, vocabulary, length

and sentence structures suitable for elderly.
•

Low pitched voices are more acceptable for speech synthesis, e.g., female voices
are less preferred than male ones.

2.4 Motor Ability

Computer mice are unsuitable for many elderly due to the lack of good hand-eye
coordination and decline of fine motor abilities (cf. [12]). Positioning the cursor is
difficult if the target is too small or too irregular to locate, and fine movements are
harder to control (cf. [13]).Thus, the following procedures are suggested:

• Direct interaction is recommended, e.g., touch screen.

• All GUI items should be accessibly shaped, sized and well spaced from each other.