The development of puppies' senses. The dalmatian litter has reached six weeks old. As a breed they are susceptible to deafness, so they are taken for to the vet for a crucial hearing test. A new litter of golden doodles reveal how puppy eyesight develops week by week, cameras track the progress of a springer spaniel as he begins training to become a mountain search-and-rescue dog, and the labrador puppies reach six weeks old - time to find out if they have the senses and skills to pass their guide dog test.