The premise that attentional resources are more restricted as the level of
arousal increases. See: Easterbrook (1959).
One of two types of sweat glands, the eccrine glands influence
electrodermal activity as measured in PDD. They are found throughout the
skin surface of the body, but in highest concentration on the hands and feet.
See Handler et al. (2010)
Neurons that carries nerve impulse from the central nervous system to
the effector organ or muscles. Also called motor nerves.
PDD scoring rule forwarded by Cleve Backster and used exclusively in
the Backster Zone Comparison Technique. According to the rule, if a relevant
question does not evoke a physiological reaction, it is scored against the
adjacent comparison question with the larger reaction. If the relevant question
does produce a significant reaction, it is compared to the comparison question
with the smaller reaction. See: Matte (1996); Meiron, Krapohl & Ashkenazi
Electrocardiogram (EKG or ECG)
Tracing of the electrical activity of the heart. This endosomatic waveform
consists of the P, Q, R, S, T, and U waves. The search for diagnostic
information in the ECG for PDD purposes has not been fruitful to date. There
are preliminary data that suggest that the pre-ejection period (PEP), which is
derived from the ECG and the impedance cardiograph (ICG), is a reliable gauge
of sympathetic nervous system arousal. Inter-beat interval has also shown
promise. See: Kircher, Packard, Bell & Bernhardt (2003).
Electrodermal Activity (EDA)
All exosomatic and endosomatic changes in the electrical properties of
the skin. See: Handler et al. (2010).
Electrodermal Response (EDR)
Reaction of skin measured by changes in its electrical properties,
including skin resistance (SR), skin conductance (SC), and skin potential (SP).
See: Handler et al. (2010).
Recording of the electrical activity of the brain generated by the firing of
clusters of neurons. In recent years EEG methodology has been applied to
deception and concealed information tests.
Tracing of the endosomatic electrical properties of the voluntary
muscles. This activity is recorded through sensors placed on the skin near the
muscles of interest. EMG could be used for the detection of physical
countermeasures when the sites are correctly chosen by the examiner.
Recording of the electrical activity produced during eye movements.
EOGs have had two principal uses in deception testing. One is as a deception
indicator. Some research has shown lateral eye movements have diagnostic
information useful in assessing whether a person harbors concealed
information. The second application is with evoked cortical potentials, which
also have been used in concealed information paradigms. Brain wave activity
generates very small voltages, and eye movements generate electrical potentials
that interfere with these signals. EOGs are often collected for subtraction from
the brain wave signals
Embarrassing personal question (EPQ)
A question, frequently with a sexual theme, sometimes used with the
Keeler Relevant/Irrelevant test in the late 1940s and early 1950s. Leonarde
Keeler experimented with the embarrassing personal question, hypothesizing
that guilty subjects would not respond to it, remaining instead focused on the
relevant questions, while the innocent examinees would produce significant
responses in the opposite pattern. The embarrassing personal question did not
have widespread use and was not taught at Keeler’s school after 1951. This
approach is proscribed in the American Polygraph Association’s Ethics and
Principles of Practice and some state polygraph laws. Later PDD examiners
sometimes asked examinees during testing if they would mind if an
unrehearsed question were asked, and then used the resulting physiological
response from this question as an indicator of response potential. In that
application, no question was actually presented.
emotional standard A term coined by Rev. Walter Summers in his research into lie detection.
The emotional standard was an emotion-provoking question to which the
examinee answers truthfully, but one that the examinee would prefer to hide.
It was included in a test series so the reaction evoked by it could be compared
with the reaction elicited by relevant questions. Summers’ test format included
an established ordering of pairs of relevant and emotional standard questions,
interspersed with irrelevant questions, as needed. It is the first report in the
literature of this type of question, and it predates Reid’s “comparative response
question”. See: Summers (1939).
An approach based entirely on observation rather than speculation.
Much of PDD research is empirical in nature, though several theories exist.
Empirical Scoring System
The Empirical Scoring System (ESS) is an evidence-based numerical
scoring model for manual test data analysis (TDA) of PDD test data from
examinations conducted using comparison question test (CQT) formats. The
ESS includes a description of the physiological data features that are correlated
with truth and deception, mathematical transformation methods for assigning
and aggregating numerical scores, decision rules for the classification of
numerical scores as indicative of truthfulness or deception, and numerical
cutscores that define the a priori thresholds of statistical significance. ESS
cutscores are based on normative data that allow for calculation of the
probability of an erroneous test result. Thus, the ESS allows for the selection of
statistically optimal cutscores based on operational needs for the resolution
and precision of the test result. See: Blalock, Cushman & Nelson, (2009);
Handler, Nelson & Blalock (2008); Nelson, Krapohl & Handler (2008).
Employee Polygraph Protection Act of 1988 (EPPA)
Federally enacted legislation that restricts the use of “lie detector tests”
by private employers except under specified conditions. Employers may not
compel or request employees or applicants to submit to such testing, nor may
they use any results for adverse action. All levels of government are exempt
from the provisions of EPPA. There are also exemptions for companies that
provide security services and those involved in the manufacture and storage of
controlled substances, who may use the polygraph for preemployment
screening. Employers may request an employee to undergo PDD testing if it is
part of an investigation of a loss to the employer, the employee had access to
the property lost, there is a reasonable belief that the employee was involved in
the loss, and the employee is given 48 hours notice prior to the examination
that outlines the loss, investigation, and the reasons the employee is under
suspicion. The employer is prohibited, however, from taking any action against
the employee who refuses to cooperate with a PDD examination. Two of the
major effects of EPPA have been a sharp decrease in the number of private
examiners in the United States, and a move by the professional polygraph
associations to upgrade standards of practice. Full text of the law can be found
on the Web at www.dol.gov/dol/compliance/comp-eppa.htm.
Something produced from within the body itself. One type of
electrodermal response, skin potential response, is produced by electrical
activity generated by the dermis. Its measurement requires the placement of
one electrode over an area well supplied with sweat glands (active site) and the
other over an area devoid of them (reference site). The active site is negative in
relation to the reference site by an amount that varies from a few to 50 to 60
mV. An alerting stimulus generally produces an increase in negative potential,
followed by a positive wave, usually commensurate with the production of
surface sweat, and sometimes a second negative wave. Similarly, EEG signals
are generated by bioelectric processes in the brain, and EKG from the heart.
For contrast, see exosomatic.
Used at the beginning and sometimes the end of Searching Peak of
Tension tests that are selected because it is known that they cannot be the
critical items or keys. They can be used to elicit the orienting responses that
some examiners think might interfere with interpretation if they occur on
possible critical items. Sometimes called padding questions.
A hormonal stimulator of the sympathetic nervous system. It acts to
constrict peripheral blood flow, raise blood pressure, increase cardiac activity,
promote metabolic activity through the release of glucose, and inhibit digestive
processes. Epinephrine is considered a psychogenic hormone because it alters
psychological processes when released in large quantities, such as under
stress. It is produced in the adrenal medulla, located immediately above each
kidney. Called adrenaline in British reports.
Computer polygraph manufactured in Russia.
error-related negativity (ERN)
Brain wave time-locked to response selection that corresponds with
incorrect choices. One of several electrocortical phenomena being investigated
as a deception detection measure.
Normal quiet respiration.
Annotations, markings, or abbreviations placed on the chart to alert a
reviewer of a significant event. Examples include; start and stop of examination
announcement, reading of question, examinee’s answer, movements, talking,
deep breathes, etc. Many event markers have generally accepted universal
Event-related potentials (ERPs)
A change in electrical activity of the brain in response to a stimulus,
recorded as changes in voltage at the scalp surface. Current signal processing
approaches allow averaging of EEG activity, and ERPs are extracted by the
averaging of brain waves over several repetitions of stimulus items. ERPs have
been useful to scientists as markers for specific processes in the brain. There
are several types of ERPs: the N100, N200, P300, and N400, to name a few.
The “N” and “P” designators are conventions for the polarity of the signal,
negative and positive. The number denotes the latency after stimulus
presentation, measured in milliseconds. The P300 has been reported to be a
dependable indicator of concealed information, though its application to
deception detection is not established. ERPs are generated by the central
nervous system, and their use in deception tests is attractive because they are
expected to be resistant to countermeasures.
Test question in which the examinee is asked about a particular piece of
physical evidence that would incriminate the guilty person. It could be items
left at the crime scene by the perpetrator, stolen property that could be
discovered in his possession, or even doubts about leaving incriminating
fingerprints. For example, if a PDD examination was being administered to
resolve a fraudulent use of a credit card, a test question could center on the
signature on a receipt, the possibility of a photograph being taken at an ATM
where the card was used, or possession of property wrongfully obtained by use
of the card. The evidence-connecting question could be more salient to the
examinee than the “did you do it” relevant question because the examinee
knows it can lead to physical evidence that will implicate him.
Evidentiary Decision Rules
Decision rules proposed by Krapohl (2005) that begin with asymmetric
cutting scores: if the grand sum of scores is -6 or lower, the call is DI; if the
grand sum of all scores is +4 or greater, the call is NDI. In those cases where
the grand sums ranged from -5 to +3, the sub-totals (Spot Scores) are
evaluated. For those cases, if a single relevant question has a sub-total of -3 or
below, the decision is DI. All other cases are called Inconclusive. See Krapohl
(2005); Krapohl & Cushman (2006).
A polygraph examination in which the written and stated purpose agreed
to by the parties involved is to provide a diagnostic opinion as evidence in a
pending judicial proceeding
Evoked Cortical Potentials
Brain waves that are induced by stimuli controlled by the experimenter.
The entirety of the PDD process, including pretest, test, and post test
elements, from onset to completion.
Exclusive (Exclusionary) Comparison Question
Probable-lie comparison questions that do not overlap the event covered
by the relevant issue questions. There is a school of thought that examinees
may confuse the relevant questions with the comparison questions unless
these two types of questions are designed to avoid any degree of overlap. This
is accomplished by constructing comparison questions that are different from
the relevant issue by time period, location, or type of activity. Although
exclusive comparison questions have better face validity over non-exclusive
comparison questions, research has supported the non-exclusionary version.
See: Amsel (1999); Podlesny & Raskin (1978); Horvath (1988); Horvath &
A PDD examination offered to an accused against whom other strong
evidence exists. The exculpatory examination is often used in the military
services when urinalysis has indicated a service member has used an illegal
drug. The service member is not obligated to undergo the PDD examination
with the military investigative services, but because adverse action can be
taken based solely on the urinalysis, many avail themselves of the opportunity.
Exculpatory exams are so named because they are intended to offer an
opportunity to present evidence to support one’s assertion of innocence.
Something generated from outside the body. Electrodermal recordings
that apply a voltage or current to the skin are called exosomatic and in
polygraphy a direct current (DC) is used to measure aspects of EDA. Constant
voltage DC systems record EDA as skin conductance (SC) for which the units
are Siemens (S) or mhos, which is the inverse of ohm in both spelling and in
computation. Constant current systems measure and record skin resistance
(SR), which is measured in ohms. EDL is the accepted abbreviation for
electrodermal level and refers to the tonic or baseline level at any given
moment, while EDR is reserved for the phasic response or reactions to
stimulation. The designators R and L may be appropriately applied to the type
of measurement taken, for example SRR (skin resistance response) or SCL
(skin conductance level). Both skin conductance and skin resistance are
exosomatic measures because electrical currents are applied from outside
sources to detect the electrodermal activity. As opposed to endosomatic. See:
Handler, Nelson, Krapohl & Honts (2010).
Ex Parte Phenomenon
Literally, from the Latin meaning taken from one side or party. Legal
term that has been used to indicate the “friendly polygrapher” hypothesis. See:
In research, subjects fall into two broad categories: experimental and
control groups. The experimental group is subjected to the independent
variable—that is, the variable of interest to the experimenter. The control
group is treated exactly the same, except that it does not receive the
independent variable. When the dependent variables of the experimental and
control groups are compared, their differences are attributable to the
independent variable. Consider research examining the validity of PDD: one
group would be assigned to the innocent condition, and the other to the guilty
condition. Since the variable of interest is the detection of deception, the guilty
would be the experimental group and commit the mock crime, and the
innocent would not commit the mock crime and would be the control group.
Zone Comparison Technique test format for dealing with multiple issues.
That which is not derived exclusively from the polygraph waveforms or
tracings. Some polygraph schools teach that there are sources of information
to assist the polygraph examiner in rendering a decision that are not registered
in the physiological data. These sources of extrapolygraphic information
include case facts, behavioral indicators, and base rates. Blind interpretation
of polygraph charts is one way of parsing out what information is available in
the test recordings and that which comes from other sources.
extrasystolic beat (ESB)
See premature ventricle contraction.