Designing Effective Speech Interfaces

Predictability

The eighth law is Predictability: The interface will behave in a manner such that users can accurately predict what will happen next.

Human Factors

For users to predict how an interface will work, it must mesh well with the user's mental model.

When using an interface for the first time, people either have, or quickly create, a mental model of how the interface will work. This mental model may even exist before they start to use the interface. If they have heard or read that the new interface will be like using a tape recorder, for example, then they have the mental model of a tape recorder in place before even trying out the new interface.

People always have a mental model operating. The mental model they have may not match the conceptual model of the actual interface. If the interface is well designed, then the designers will have consciously chosen a conceptual model for the interface, after analyzing likely users and their mental models. When an interface is not consciously designed in this way, the conceptual model will not mesh well with the user's mental model.

People always have a mental model operating.

Users can and do change their mental model of a particular interface. Training can help them adjust their mental model. Their experiences with the product itself also helps to adjust their mental model.

Technology Considerations and Implications

Speech interfaces are particularly difficult to create a conceptual model for because they are usually temporal. ...