In 19th-century America, childhood play was seen as

Dr. Maizenblu was testing out a new medication used to treat depression

He had 150 participants who had varying levels of depression. Because he wanted to see whether a new drug really worked, he separated the severely depressed from the mildly or moderately depressed. He then made sure the severely depressed group actually received the drug while the other group received the placebo. What error, if any, did Dr. Maizenblu make in this experiment? a) He made no error at all. b) He did not have enough participants in the study. c) He showed selection bias. d) He showed unethical treatment of depressed people.

Inspired by Charles Darwin's work, G. Stanley Hall and his student, Arnold Gesell,

A) laid the modern foundations of ethology. B) developed the concept of sensitive periods in development. C) devised theories based on evolutionary ideas. D) constructed the first intelligence test.