The Effects of Encumbrance on Mobile Gesture Interactions

We examine mobile gesture interaction while the user is encumbered by holding bags and boxes. This is a frequent situation in everyday life and one that can cause problems when using mobile devices. A Fitts’ Law study was conducted to examine wrist rotation, a ‘hands free’ interaction method, to assess the effects of carrying objects on interaction performance. The aim was to understand if, and how, different types of objects affected usability. Users were tested standing and walking and while carrying a bag or box. Results suggested different forms of encumbrance led to significantly different levels of interaction performance, with holding the bag causing more problems than the box. The results suggest that designers should test their new interaction techniques with a range of different encumbrances to ensure that they are useful in real-world contexts.