The methodological breakthrough for the study of sleep came in 1937 when researchers began using

When we say that schizophrenia is a heritable disease, we mean that

a. a person who has inherited a "schizophrenia gene" will eventually develop the disease. b. a person inherits a tendency toward schizophrenia which may be triggered in certain environments. c. the likelihood of a person with a "schizophrenia gene" developing the disease is influenced solely by the biological family history. d. it is not possible to carry an unexpressed "schizophrenia gene." e. schizophrenia is genetically transmitted as a recessive allele.

One limitation of research questionnaires is that

a. these measures may not capture the complexity of the issues being investigated. b. such measures cannot be analyzed efficiently. c. paper and pencil measures are expensive to administer. d. these measures cannot be used in a controlled setting.