Blood pressure (BP) is one of the most frequently measured physiological variables. Its meas-
urement in the physician's office and the hospital or clinic far exceeds its use as a variable in
psychological research. This is because of its importance as a general index of cardiovascu-
lar function and health. Research on the effects of psychological stimuli on blood pressure
dates back to at least the 1920s, when Nissen, as one example, obtained blood pressure read-
ings of patients in a dentist's chair. Pressures rose sharply as soon as the dentist entered the
room! ( Woodworth & Schlosberg, 1954).

Blood volume (BV) is much less familiar than blood pressure. It refers to the amount of
blood that is present in a certain portion of body tissue at a given time. Blood volume changes
occur as a function of local metabolic requirements, and an important factor affecting it is the
behavior in which the individual is engaged. Early studies of blood volume include those of
Shepard, who reported in 1906 that the expectation of a stimulus led to decreased hand blood
volume and an increase in brain volume ( Woodworth & Schlosberg, 1954). This chapter ex-
amines BP and BV as physiological variables in psychological research. Some questions of in-
terest regarding blood pressure include the effects of cognitive load and problem solving on
this measure. Important issues concerning effects of stress, frustration, hostility, and anger on
changes in blood pressure are also considered, as are the relationships between Type A/B per-
sonality and this vital measure. In addition, social factors such as crowding and communica-
tions are examined with respect to their influence on blood pressure. The extent to which blood
pressure can be conditioned through classical and instrumental procedures is also covered.

With regard to blood volume changes as a function of psychological processes, there is
less coverage because the research in this area is not as extensive as for blood pressure.
Nevertheless, there are important issues concerning the use of blood volume measurements
in research on sexual response of both women and men, and blood volume changes during
the orienting response and instrumental conditioning. The BP and BV responses, and their re-
lation to behavior, are presented after a brief discussion of the anatomy and physiology of
these measures.

Blood vessels may be divided into several categories on the basis of their size, function, and
microscopic characteristics. These categories include the large elastic arteries, medium-size
arteries, small arteries (arterioles), capillaries, veins, and venules ( Jacob & Francone, 1970).
The blood vessels are composed of three layers: an inner tunica intima, a middle tunica
media, and an outer tunica adventitia. (Note the direct use of the Latin word for a layer of

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