not usually under conscious control. Right now, you are not telling your heart, “Beat,
beat, beat,” yet your heart is beating. You are not thinking, “Breathe, breathe,
breathe,” yet you are breathing. These functions are being controlled through your
autonomic nervous system. The autonomic nervous system is divided in its
functions: the parasympathetic nervous system (PNS) and sympathetic nervous
system.
(i) The parasympathetic nervous system is the “housekeeping” or braking system.
It is responsible for conserving energy and making sure necessary bodily
functions such as digestion and waste elimination take place. It also functions
3. PSYCHOPHYSIOLOGICAL BASIS OF THE FORENSIC ASSESSMENT
19
to restrain sympathetic arousal and attempt to maintain homeostatic norm.
In doing so, it conserves physiological resources.
(ii) The sympathetic nervous system is our emergency or action system. It is the
system that causes the sudden and dramatic changes manifested in the example
cited previously.
The brain is in constant struggle with various psychological and physiological stressors to
maintain or regain homeostasis through managing the competition of the parasympathetic
and sympathetic nervous systems. The brain slows the heart down by sending it a parasym-
pathetic neural message, or speeds it up by sending it a sympathetic message. It is constantly
performing a cardiac-output physiological balancing act.
Generally, the parasympathetic nervous system increases abdominal activity, allowing
for digestion and waste elimination, while it slows thoracic (chest) activity and conserves
energy by slowing the heart rate, lowering blood pressure, and decreasing the rate of
breathing. The sympathetic nervous system decreases abdominal activity (there is no need
for digestion or waste elimination under conditions of dire threat) and increases thoracic
activity in an attempt to get more oxygen to the critical areas of the body necessary to assist
in survival (Figure 3.1).
Thus, the parasympathetic nervous system is constantly trying to balance the activity of
the sympathetic nervous system in order to conserve energy and prevent bodily dysfunc-
tion. However, frequently its efforts are defeated. When this occurs, sympathetic arousal
takes place, causing sudden involuntary changes to prepare for the threat. The heart rate
is increased and additional levels of adrenaline are secreted into the blood. The combination
of an increase in cardiac output and adrenaline causes an increase in blood pressure. Addi-
tional red blood cells are released from the spleen to increase the amount of oxygen deliv-
ered to the body cells and remove the additional waste products produced by the excited
metabolism.
The underlying physiology is also stressed. The liver, fat, and muscle tissue which store
energy as glycogen are infiltrated by adrenocorticotropic (ACTH) hormones. These hor-
mones immediately help convert energy stored in these areas to actual energy to be
released into the bloodstream. Research has established that ACTH also affects mind func-
tion and improves memory. Endorphins, which are natural narcotics, are simultaneously
released into the bloodstream (this pseudopharmaceutical mechanism assists us in not
experiencing pain from injuries incurred until after the fight). The endorphins also help
FIGURE 3.1 Overview of parasympa
Increases
Increases
thetic/sympathetic controls of the body.
abdominal activity
thoracic activity
Sympathetic
Parasympathetic
Decreases
Decreases
abdominal activity
thoracic activity
20
3. PSYCHOPHYSIOLOGICAL BASIS OF THE FORENSIC ASSESSMENT
you overcome your fear of the situation. Clotting enzymes are released to prevent profuse
bleeding. There is vasoconstriction of the peripheral arterioles, which redirects the blood
supply away from the skin surfaces to other parts of the body (this decreases the amount
of blood that will be lost in case of injury, and causes the “ghost white” appearance often
observed in people experiencing fear).
In conjunction with the foregoing changes, there will also be a combination of differen-
tiated vasoconstrictions and vasodilatations, as blood is rerouted from areas of less impor-
tance to areas of primary importance in the body, or the body’s core, during the emergency.
There is an increase in sweat gland activity to help cool the body down and act as a lubri-
cant to help prevent abrasions during a fight. Palmar sweat (moisture in the hand) also pro-
vides for a better grip. The hair may stand on end (piloerection or goose bumps). This
physiological mechanism of raising the hair helps cool the skin surface, allowing air to cir-
culate more freely over it. In earlier periods of our species evolution – before clothing – this
hair “standing on end” may have served to make us look larger, fiercer, and less palatable
to predators (Figure 3.2).
The interaction of the two branches of the autonomic nervous system is clearly seen and
felt (Figure 3.3). Sympathetically, visual and hearing acuity increase, maintaining the individual in a heightened state of awareness. As the pupils dilate, more light is admitted,
extending far vision. Sympathetically, the salivary glands are inhibited. They are part of
the digestive system and considered unimportant during fight/flight. This causes the
“dry mouth” phenomenon utilized by earlier cultures in trials by ordeal.
Some research suggests that memories imprinted during this heightened mental state are
more vivid and may account for “reliving” and highly accurate recall experienced by trau-
matized individuals. Others may argue that the endorphins may explain why victims of
traumatic injury often do not remember it. Whichever occurs, one thing is certain: the
mind-body’s sympathetic arousal during a threat is a highly evolved process designed to
totally protect the individual during emergencies and afford it the best chance for survival.
The parasympathetic nervous system is the “ying” to the sympathetic nervous system’s
“yang.” Its job is to bring the body back into homeostasis – to conserve precious energy to
FIGURE 3.2
3. PSYCHOPHYSIOLOGICAL BASIS OF THE FORENSIC ASSESSMENT
21
Parasympathetic
Sympathetic
Constricts
Eye
Dilates
Stimulates
Salivary glands
Inhibits
Slows
Breathing
Increases
No comparative
Sweat glands
Increases
Slows
Heart
Accelerates
Stimulates
Digestion
Inhibits
Stimulates
Waste elimination
Inhibits
FIGURE 3.3 The autonomic nervous system.
“calm” the physiological seas, so to speak. If the parasympathetic nervous system should
overcompensate as it attempts to return the body to its prethreat norm, involuntary urination
or even defecation may result. Many police officers have often taken note of how, on occa-
sion, th
ey responded to the scene of a burglary only to find human feces in the middle of
the floor. Some people theorize that this defecation is sexually or socially related behavior,
but it is likely that it is caused by the overcompensation of the parasympathetic division,
after the strong sympathetic arousal caused by fear of detection associated with committing
a burglary. This overcompensation explains why people sometimes faint during extreme
emergencies, and why deceptive suspects often display leaning/supportive behaviors.
Although the forgoing example was one of perceived physical threat, the responses to
psychological or even supernatural threat are similar. A guilty suspect may become weak
in the knees or appear to lose balance and have the need to support himself during the per-
iods of greatest threat. Extreme sympathetic and parasympathetic arousals appear most
obviously in cases where there are reports of death caused by “voodoo” curses. Victims
who strongly believed they had been cursed would die after displaying chronic symptoms
of fright (sympathetic arousal), which depleted their adrenaline, causing death due to low
blood pressure [2]. Alternatively, sympathetically/parasympathetically induced voodoo
death can also be caused by hypovolemic shock. This results from the constant heightened
state caused by sympathetic arousal: victims’ intestines lack the necessary blood and fluids
to sustain cell life, and organ necrosis and death results. Whichever explanation applies in a
given instance, these cases clearly validate the General Adaptation Syndrome postulated by
Hans Selye, a Canadian physiologist [3], and the need for the body to be able to regain a homeostatic norm.*
*Selye reported that on experiencing distress, the body entered an “alarm” stage, where psychophysiological
factors were heightened. The body next entered a stage of “resistance,” where it attempted to overcome the
distress. If the body was unable to correct the problem, it entered into a stage of “exhaustion,” which
ultimately led to death.
22
3. PSYCHOPHYSIOLOGICAL BASIS OF THE FORENSIC ASSESSMENT
Usually alterations to the body’s homeostatic norm are not drastic or life threatening.
They are, however, clearly measurable, and measuring changes in three of the body’s sys-
tems is the basis for the polygraph examination. During a polygraph examination, the
examinee is attached to the polygraph instrument, and several charts of data are collected
while the examinee answers only “yes” or “no” in response to the questions asked. Requir-
ing only yes or no answers minimizes vocalization and subsequently reduces distortion cre-
ated in the breathing pattern of the examinee, which is inherent in prolonged speech
patterns. In addition to breathing, the polygraph instrument records electrodermal skin
activity and cardiovascular changes, such as changes in pulse rate, mean blood pressure,
and blood volume [4].
Moreover, the same physiological changes, in one degree or another, that are recorded
on a polygraph instrument also appear during the telling of a lie in an interview when
the subject experiences undue stress caused by the fear of detection. While the polygraph
technique elicits one series of measurable changes, consider the greater number of
additional, observable physiological changes suppressed using this technology. Many phys-
iological changes caused by the tremendous energy and strength the body is producing
during this heightened state of arousal, which would cause changes in body position and
nonverbal behavior, cannot be assessed because of the subject’s instructions to sit still.
The forensic interviewer, on the other hand, is not limited only to observing changes in
the three physiological parameters that the polygraph monitors. He or she is trained to
make global use of the senses to detect leakage of deceptive behavior, regardless of how
it occurs, during the Forensic Assessment Interview. Understanding why these changes
occur and how to recognize them will enable the reader to determine truth or deception
and separate innocent from guilty suspects.
It is a given that the sympathetic nervous system kicks into action whenever the
brain perceives a threat. In considering data presented to the interviewer as a result of
sympathetic enervation, we should be aware of the work of W. B. Cannon. Cannon, a famous
Harvard psychologist, reported that when a cat was fed a meal containing a radiation-opaque
substance and placed on a table so an x-ray of its stomach could be taken, digestion went on
normally. The cat’s stomach made rhythmic movements known as peristaltic action. When a
dog was brought into the room, which represented a threat to the cat’s well-being, the cat
became sympathetically aroused, and its digestion suddenly ceased.
The question remains: Why does telling lies constitute a threat significant enough to
cause this sympathetic enervation? There are several theories for this cause–effect relation-
ship. They include conditioning, approach-avoidance conflict, and psychological set (also
referred to as “salience”) [5].
Classical or Pavlovian conditioning [6] was discovered by the Russian physiologist Ivan
Pavlov, while he was attempting to study salivation in dogs. To start the dogs salivating,
Pavlov presented them with food. His experiments were disrupted when just the sight of
him or his assistants caused the dogs to begin salivating even before food had been pre-
sented. Pavlov realized that salivation could be psychologically caused; and, he had taken
on a special relationship with food in the minds of the dogs. Every time he had previously
entered the room the dogs were presented with food. Now, just the sight of him caused
salivation.
3. PSYCHOPHYSIOLOGICAL BASIS OF THE FORENSIC ASSESSMENT
23
Pavlov called the presentation of food an “unconditioned stimulus” (UCS), which he
described as any stimulus capable of causing a reaction to occur without any prior training
or learning having taken place. Pavlov labeled the reaction or response that occurred when
a UCS was presented an “unconditioned response” (UCR). In Pavlov’s chance discovery,
food was the UCS, and salivation was the UCR. Pavlov theorized that if a neutral stimulus
(NS), such as himself, were paired enough times with a UCS (i.e., food), then the NS would
take on the properties of the UCS and cause the UCR (i.e., salivation) to occur, even though
the UCS was not present. The neutral stimulus had become a “conditioned stimulus” (CS),
and the UCR was now a “conditioned response” (CR) (Figure 3.4).
When a child is caught doing something “wrong” (wrong behavior can be very subjec-
tive) by his parents, he is yelled at, disapproved of, spanked, or in some other way pun-
ished. This automatically causes sympathetic arousal to occur. Punishment is the UCS,
and sympathetic arousal is the UCR. Throughout our lifetimes, when we tell self-serving
lies and get caught, we are punished. Lying, therefore, becomes associated or paired with
punishment. It becomes a conditioned stimulus (CS), which can then cause a conditioned
sympathetic arousal to occur (Figure 3.5).
A second explanatory theory is that of “conflict” [5]. Anytime mental conflicts occur, we experience emotional changes that, in turn, ca
use physiological changes to occur. If you
have the choice of going to a movie or to a football game, and you really want to do both,
you are experiencing an approach-approach conflict. The greater your desire to attend both
events, the greater the conflict would be, and the greater the resulting physiological changes
that will be created. Avoidance-avoidance conflict results from having to choose between
two negatively impacting options. The greater the negative impact of the options, the
greater the accompanying physiological response.
FIGURE 3.4 Classical/Pavlovian conditioning.
Food
Salivation
(UCS)
(UCR)
Pavlov
(Neutral stimulus)
FIGURE 3.5 Conditioned response to a lie.
Punishment
Sympathetic arousal
(UCS)
(UCR)
Caught telling a lie
(CS)
24
3. PSYCHOPHYSIOLOGICAL BASIS OF THE FORENSIC ASSESSMENT
When an action causes something desirable or undesirable, with neither being predict-
able, it is called an approach-avoidance conflict. A laboratory rat in a Skinner box** is taught that by pressing a lever it will receive a reward of a food pellet. When the experimenter unpredictably alternates the outcome by intermittently introducing a punishment
of an electric shock when the lever is pressed, the rat does not know whether it will be
rewarded with food or punished with an electronic shock. The rat wants to receive food,
but fears receiving an electric shock, and it now experiences an approach-avoidance con-
flict, because the same action can produce either outcome.
Like the rat in the Skinner box, an individual telling a lie also places himself in an
approach-avoidance conflict. He is asked a question by the interviewer and answers with
a lie. If he gets away with his deception, he is rewarded. If his lie is detected, he is punished.
He is unsure what the result will be. The greater the reward and punishment, the greater
the mental conflict will be, and the greater the accompanying sympathetic arousal.
A third possible theory involves the psychological concept of cognitive dissonance.
When a person holds two contradictory ideas simultaneously, he will experience an uncom-
fortable feeling [7]. The “ideas” or “cognitions” in question may include attitudes and
beliefs, the awareness of one’s behavior, and facts. This theory is one of the most influential
Nathan J Gordon, William L Fleisher Page 5