Naturalness influences the perceived usability and pleasantness of an interface’s sonic feedback

This study examined the influence of the naturalness of a sonic feedback on the perceived usability and pleasantness of the sounds used in a human-computer interface. The interface was the keyboard of an Automatic Teller Machine. The naturalness of the feedback was manipulated by using different kinds of relationship between a keystroke and its sonic feedback: causal, iconic, and arbitrary. Users were required to rate the naturalness, usability, and pleasantness of the sounds before and after manipulating the interface. Two kinds of interfaces were used: a normally functioning and a defective interface. The results indicated that the different relationships resulted in different levels of naturalness: causal mappings resulted in sounds perceived as natural, and arbitrary mappings in sounds perceived as non-natural, regardless of whether the sounds were recorded or synthesized. Before the subjects manipulated the interface, they rated the natural sounds as more pleasant and useful than the non-natural sounds. Manipulating the interface exaggerated these judgments for the causal and arbitrary mappings. The feedback sounds ruled by an iconic relationship between the user’s gesture and the resulting sounds were overall positively rated, but were sensitive to a potential contamination by the negative feelings created by a defective interface.