What percentage of people who have PTSD also have a comorbid disorder?

Research procedures that may harm a child physically or psychologically should ____

a. only be used when necessary b. only be used when a parent gives consent c. never be used d. only be used when the researcher is very careful

Which of the following types of rewards has been shown not to increase performance?

a. Financial b. Non-financial c. Social d. All three can increase performance