Who was a subject in Wertheimer's research on the perception of apparent movement?

A child is awakened during the night, uses the toilet, and receives a sticker and praise from a parent. Later in the week, accumulated stickers may be turned in for a highly desired toy. This child is undergoing:

A) dry-bed training for enuresis. B) dry-bed training for encopresis. C) bell-and-battery therapy for enuresis. D) bell-and-battery therapy for encopresis.

Studies of at-risk infants suggest that

a. at-risk infants will have unstable family environments. b. an unstable environment does not affect the development of at-risk infants. c. regardless of the environment, at-risk infants are likely to lag behind infants not at risk. d. with a stable, supportive environment at-risk infants often develop normally during childhood.