An hypothesis represents a combination guess and prediction regarding what results should be found from a scientific research study. In order for a test to be reliable for any purpose, it must necessarily be valid for a particular purpose. In order to satisfy methodological requirements for a true experiment, subjects must be chosen randomly from populations of interest to the researcher. According to Gilpin, active deception is necessary in order for any psychological research with human subjects to be valid. True random sampling of subjects or observations guarantees an investigator will obtain research results which represent the original population of interest very typically.
Hormones can function in much the same way as non-hormonal neurotransmitters.
In order for a person to produce a reflex response, he or she must detect an external stimulus, and make a conscious decision about how to respond to it. Korsakov's Syndrome, marked by an unusual inability to remember childhood memories, appears to result from prolonged alcohol consumption. Scientific paradigms involve shared sets of assumptions regarding what scientists are supposed to study, and how they study it. The key historical figure credited with starting the Psychoanalytic school of psychology was John Watson. A major difficulty faced by introspectionist psychologists like Wundt was lack of agreement on research results obtained in different laboratories.