The human-animal relationship frequently involves physical touch, and this may have benefits for both participants. Grooming of horses at the withers has a calming effect on recipients, a phenomenon regularly used to reward horses. No studies on the effect on heart rate of grooming in different anatomical areas have been conducted in dogs, even though they are often given physical contact as a putative reinforcer. Kennelled Greyhounds (n = 16) and guide dogs (Golden Retrievers, Labrador Retrievers and their crosses, n = 12) were stroked for eight minutes using a grooming device in each of four areas in random order. These sites were selected on the basis of their being innervated by the dorsal branches of the spinal nerves, lateral branches of the spinal nerves, ventral branches of the spinal nerves and the caudal nerves. Heart rate measurements were taken every 30 seconds using an ECG recorder. There were no observed differences in the mean heart rate based on the region of the body groomed (p = 0.893), nor was any interaction of any other factor with area of the body significant (all p > 0.5). However, for all dogs, there was a highly significant trend (overall reduction) over time (p < 0.001), and Greyhounds had consistently higher mean heart rates than guide dogs (p < 0.001). Within Greyhounds, groomed dogs had significantly lower mean heart rates than non-groomed animals (n = 8, p = 0.003). That is, grooming had a substantial effect on reducing heat rate, but the area of the body where grooming was conducted was not important. In addition, males had consistently lower heart rates than females (p < 0.001). If having a reduced heart rate is a sign of reduced stress, then we can assume that non-invasive interventions that have this effect are reinforcing. The extent to which all dogs are reinforced by physical contact depends on their socialization and familiarity with personnel. The intrinsic reinforcing value of physical contact for dogs seems likely to be outweighed by its effect as a secondary reinforcer.