Multisensory integration with a head-mounted display: role of mental and manual load

The aim of this study was to replicate the finding that multisensory integration with a head-mounted display (HMD) is particularly difficult when a person is walking and hearing sound from a free-field speaker, and to extend the finding with a response method intended to reduce workload.

HMDs can support the information needs of workers whose work requires mobility, but some low-cost solutions for delivering auditory information may be less effective than others.

For the study, 24 participants detected whether shapes moving on the HMD screen made a sound appropriate to their forms when they collided with other shapes. Independent variables were self-motion (participants were mobile or seated), sound delivery (free-field speakers or an earpiece), and response method (noting mismatches via a mental count or via a manual clicker).

Unexpectedly, overall mismatch task accuracy was worse with the clicker (p = .027) than without. Participants also reported that it was harder to time-share the mismatch task with clicker responses (p = .033). In the clicker condition, self-motion and sound delivery interacted but in the opposite direction to the previous study.

The best way of delivering auditory information to mobile workers performing a multisensory integration task with an HMD may depend on whether responding involves mental load or manual load. Broader theories are needed to capture factors influencing performance.

Until more powerful theory is developed, designers should perform careful formative and summative tests of whether the activities to be performed by mobile HMD wearers will make some sound delivery solutions less effective than others.