In the study, dogs were given either milk or water depending on a tone that was played. Once they had learned which tone came with the "treat," the experimenters began playing ambiguous tones. If the dogs responded to the ambiguous tones, they were rated as optimistic—they expected good things to happen. While those that did not were more pessimistic. Dr. Starling's research could help in selecting which dogs make better bomb sniffers (risk-taking, optimistic) versus service dogs (risk-averse, pessimistic).