Modifications were made to difference tests on the basis of psychophysical theory and tested using a model system. The A-not A test was modified by the addition of sureness judgements to free the test from response bias; ‘warm-up’improved test sensitivity. Regular duo-trio tests were modified by using the weaker stimulus as the standard, increasing test sensitivity. The paired comparison cannot be used unless the dimension of the difference can be described. However, the warm-up procedure allows opportunity for judges to describe the difference and their own words can then be used for the test. The resulting warmed-up paired comparison was more sensitive than any modification of the duo-trio.