Many pet dogs exhibit problem behaviours which can be corrected through the judicious use of positive and negative reinforcers in training. However, animals often vary in their sensitivity and response to these. It is hypothesised that this variation may offer a biological basis for discriminating between animals that develop certain types of problems (eg fears and phobias) and their response to treatment. The development of a clinical tool that uses owner report to measure individual differences in positive and negative activation in pet dogs is described. The activation scales each measured a single homogeneous construct and effectively differentiated between individuals, demonstrating variation on two dimensions. Test-retest reliability was good and the study provided evidence of validity. Normative data were calculated and may be used in future research that could provide further evidence of validity and in investigations of the underlying structure of canine behaviour disorders. The final scales comprised of 21 items, and so can be administered with little difficulty.