Designing Effective Speech Interfaces

Modal Integrity

The third law, Modal Integrity, states: The interface will fit individual tasks within whatever modality is being used: auditory, visual, or motor/kinesthetic.

Human Factors

Some tasks are best performed using speech, others using vision, or others with motor/kinesthetic or tactile modes. Still others are best performed using multiple modes (multi-modal).

In research done by Wickens (1984), subjects performed one of two tasks, verbal or spatial. The type of input and output was varied: input for some subjects was auditory and for others was visual. Output was either spoken or manual. For verbal tasks, performance was best with auditory input and spoken output. Performance was worse with visual input and manual output. For spatial tasks, performance was best with visual input and manual output. It was worse with auditory input and spoken output.

Robert Bailey (1982, 44) notes that people can perform multiple tasks in multiple modes if they have a high skill level in both activities. Sanders and McCormick (1993, 169) provide information on the advantages and disadvantages of presenting information in a visual mode versus an auditory mode. The auditory mode is especially effective when

People can perform multiple tasks in multiple modes if they have a high skill level in both activities.

• information is short and simple.
• information is needed immediately, but not later on (does not have to be remembered).
• information is temporal in nature (refers to events over time). ...