This paper proposes a theory to account for effects of underload on performance. Malleable attentional resources theory posits that attentional capacity can change size in response to changes in task demands. As such, the performance decrements associated with mental underload can be explained by a lack of appropriate attentional resources. These proposals were explored in a driving simulator experiment. Vehicle automation was manipulated at 4 levels, and mental workload was assessed with a secondary task. Eye movements were also recorded to determine whether attentional capacity varied with mental workload. Results showed a clear decrease in mental workload associated with some levels of automation. Most striking, though, were the results derived from the eye movement recordings, which show attentional capacity varies directly with level of mental workload. This data fully supports the predictions of the new theory, which suggests that future vehicle designers should employ their technology in driver support systems rather than in automation to replace the driver. Implications of this theory are discussed. (Author/publisher)
Abstract