Evaluating the two-component inspection model in a simplified luggage search task.

Visual inspection of X-ray images of luggage is a time-pressured task that typically shows large initial training effects, but there exists a paucity of models capable of evaluating performance and speed concurrently. In the present study, visual inspection ability during learning was modeled using Drury's two-component inspection model (TCM; Drury, 1975) in a laboratory experiment involving 12 younger (mean age=20.8 years) and 12 older (mean age=60.0 years) naive participants undertaking a simplified luggage search task. Model fits and assumptions were found to be reliable and accurately reflected improvement with training for decision time, although neither search nor decision components of the model individually showed a significant effect of age. The decision component of the model showed larger improvement with training than did the search component, and stopping-time policy accurately reflected the improvements found between ages and within training levels. The TCM is a useful supplement to detection theory when speed of performance is a factor.