Josie, the author's dog niece, has dark, friendly eyes. Maria Osborne Human pupil size tends to decrease with age, because the muscles that respond to light lose some of their strength over time.

The simple conclusion was that dark eyes on a dog tend to send a non-threatening and more inviting gaze signal to human beings. Those soulful brown eyes might stir some, people to write poems ...

Dark-eyed dogs are rated as friendlier and more puppy-like. Brown eyes may have been specifically selected for during the domestication of dogs.