7 Matching Annotations
  1. Oct 2020
  2. Jul 2020
  3. Jun 2020
  4. Nov 2017
  5. Oct 2017
  6. Nov 2015
    1. As rats age, their chirping generally becomes less frequent. (A similar phenomenon seems to occur in humans: Research done by William Fry, a professor emeritus at Stanford University School of Medicine, has found that kindergarteners laugh 300 times a day, whereas adults laugh just 17 times.) However, rats who were tickled often when young usually retain their tendency to chirp later in life.