A system for assessing a mental health disorder in a human subject, the system comprising: a display configured to display a series of natural test images to the subject； an input by which the subject can input a response, following the display of each test image, as to whether or not the test image satisfies a predetermined categorisation criterion； a control processor configured to control the display of the test images by the display, to measure the duration of time from when each test image is initially displayed to when the corresponding response is input by the subject, and to generate a set of response data including the response times in respect of each of the test images； and a data processor configured to process the set of response data and to compare the processed response data with reference data to assess whether or not the subject has, or is likely to develop, the mental health disorder.
