Methods and apparatus for modifying a user interface as a function of the detected emotional state of a system user are described. In one embodiment, stress analysis is performed on received speech to generate an emotional state indicator value, e.g., a stress level indicator value. The stress level indicator value is compared to one or more thresholds. If a first threshold is exceeded the user interface is modified, e.g., the presentation rate of speech is slowed. If a second threshold is not exceeded, another modification to the user interface is made, e.g., the speech presentation rate is accelerated. If the stress level indicator value is between first and second thresholds, user interface operation continues unchanged. The user interface modification techniques of the present invention may be used in combination with known knowledge or expertise based user interface adaptation features.