Terms Relating to Lie Detectors Explained – Letter P
Event-related potential (ERP) of the brain measured at the scalp that has
an average latency of 300 milliseconds from stimulus onset and is recorded
maximally at site PZ in the International 10-20 System. The P300 is related to
unique characteristics of the stimulus, and is most often associated with the
“oddball” or rarely occurring stimulus. For example, the P300 is known to be
evoked by a low incidence auditory tone that is of a different pitch than another
tone that is occurring much more frequently. A P300-based Concealed
Information Test has been developed for criminal testing, though field testing is
incomplete. See: Farwell & Donchin (1991); MacLaren & Taukulis (2000);
An alternate expression for irrelevant items in a Known Solution Peak of
Tension test. In some reports, padding relates to only the first or last one or
two items in these tests.
Special type of physical countermeasure in which an examinee will
attempt to evoke physiologic responses by covertly self-inducing discomfort.
Included in this group are strategies such as biting the tongue, pressing
against a sharp object in the shoe, forcing a fingernail into the thumb cuticle,
and irritating a wound. While spontaneous use of these tactics has not been
found effective, they can be more powerful when the examinee receives training
and feedback. See: Honts, Raskin & Kircher (1994); Krapohl (1996).
Term used in PDD to denote a single physiological data channel, such as
the pneumograph, cardiograph, etc.
Example or model. Experimental paradigms attempt to explain real
world phenomena by assessing the critical elements and their relationships
with one another.
Parasympathetic Nervous System
One of the three divisions of the autonomic nervous system also referred
to as the craniosacral system because the preganglionic neurons lie in those
areas. Parasympathetic ganglia anatomically lie in or near the organs they
innervate thus allowing for more localized control. Functionally, it is involved
in conservation and restoration of energy. The parasympathetic and
sympathetic divisions of the autonomic nervous system function to maintain
An agent whose effects mimic those resulting from stimulation of
parasympathetic nerves, especially those produced by acetylcholine.
Device used by Rev. Walter Summers to perform deception tests in the
1930s. Researchers had to order Pathometers from Fordham University, and
they were only assembled upon order. Summers conducted testing on
hundreds of subjects using this recording galvanometer and a testing
procedure he devised that included what would be later known as comparison
questions. See: Summers (1939).
Peak of Tension (POT)
Family of recognition testing procedures, including known solution,
searching (probing), concealed information and stimulation tests. A Known
Solution POT (KSPOT) is used to determine whether the examinee is aware of
details of a crime that have been kept from the general public and would
presumably only be known to the perpetrator of the crime or those with
incriminating knowledge. A Searching POT (SPOT) is used to determine details
of a crime that are not known to officials, such as the location of an
unrecovered body, but would be known to a participant in the crime. The
Concealed Information Test can be used in either the known solution or
searching condition, and is differentiated from the former two tests primarily on
the number of tests given, and the random placement of the critical item in the
test list. Stimulation tests come in several varieties and are covered in more
detail under that heading. The evaluation criterion of Peak of Tension strip
charts is simply identifying the point in the tracings where physiologic arousal
has peaked, hence the name. Peak of Tension tests are not generally used to
determine truth or deception, but rather to assist in the investigation or
Pearson product-moment correlation
A test of correlation between two sets of interval level data (see scale of
data). The coefficients will lie between -1 and +1. A value of 0 would indicate
no correlation, while -1 and +1 would mean perfect negative and positive
A device that measures penile engorgement resulting from
vasocongestion, sometimes used in psychological evaluation of sex offenders.
The reliability and validity of this procedure in clinical assessment have not
been well established, and clinical experience suggests that subjects can
simulate response by manipulating mental images. See: DSM-IV p. 524.
Suction bulb with plastic tube used to draw ink from the reservoir,
through the pen, to the pen tip. Used on old analog polygraphs with
community ink systems.
Peripheral Nervous System
Portion of the nervous system resident primarily outside of the brain and
spinal cord. The cell bodies of the preganglionic sympathetic neurons lie in the
spinal cord and those of the parasympathetic branch are situated in the brain
Rarely used term for relevant question.
Computer polygraph manufactured in the Peoples Republic of China.
The designation of “PG” by the Chinese was for “polygraph” in English.
Any bone of the fingers and toes. In research and as commonly
practiced in PDD, electrodermal sensors are attached to the distal phalanx, or
end of the finger tips. Plural is phalanges.
Class of countermeasures in which the examinee attempts to affect the
polygraph recordings through the use of ingested drugs or application of topical
preparations. See: Krapohl (1996).
A relatively rapid reaction, characterized by a relatively rapid change
from and return toward baseline.
The PPG uses the reflection of a red light emitted into the skin to detect
changes in the volume of blood in the upper layers of skin, typically recorded at
the finger when using a polygraph. Physiological arousal is marked by a
constriction in the pulse amplitude as blood is shunted from the extremity
during activation of the sympathetic nervous system. See: Geddes (1974);
Hander & Krapohl (2007); Kircher & Raskin (1988).
A polygraph created by C.W. Darrow in the 1930s. It was one of the
most elaborate polygraphs of that era, recording relative blood pressure, skin
resistance, respiration, reaction time, and bilateral hand tremors. It had two
stimulus markers, one activated by hand and the other was a voice key.
Costing upwards of $2,000 and requiring a separate technician to operate,
Darrow’s photopolygraph was primarily a laboratory instrument and was not
used extensively by the PDD community. Also called the Darrow
Photopolygraph. See: Darrow (1932).
Class of countermeasures in which the examinee attempts to manipulate
the polygraph recordings through the discreet use of movements. Some of
these movements are also used to self-induce pain. See: Honts (1987);
Computer polygraph developed and manufactured in Russia. It records
electrodermal activity, vasomotor activity, blood volume, thoracic and
abdominal breathing, motor tremor, and speech. The company URL is:
Contraction of the piloerector muscles in the skin that erects hairs and
produces “goose flesh.” One of the symptoms of a sympathetic nervous system
activation. Sometimes called piloerection.
Nonexistent lie-specific physiological response. The expression
sometimes used by polygraph critics to deride the notion that the act of
deception produces stereotypical physiological response patterns.
Procedure or substance with no intrinsic effect but is useful to convince
the patient or subject that an effective treatment has been applied. Placebos
often have effects that are attributable to suggestion. They are used
extensively in medical research for control purposes during drug testing and for
certain psychosomatic illnesses. In PDD it addresses one type of mental
countermeasure whereby examinees use ritual objects, incantations, or other
ineffectual actions with the expectation that the power of the polygraph to
uncover deception will be impeded.
A device used to measure relative changes in blood volume and pulse
volume. The three most commonly used are (a) changes recorded using a
strain gauge, (b) impedance changes and (c) photoelectric changes. It is the
third technique that is used in modern polygraphy to measure the relative
changes in pulse volume associated with the vasomotor response, usually at
the distal phalange of one of the examinee’s fingers.
A device that records respiration, and one of the three traditional
channels of the modern polygraph used in PDD. Most contemporary
polygraphs use two pneumograph recordings: abdominal and thoracic. The
types of sensors include the traditional corrugated rubber tube, the mercury
strain gauge, or the newer piezoelectric.
By definition, an instrument that simultaneously records two or more
channels of data. The term now most commonly signifies the instrument and
techniques used in the psychophysiological detection of deception, though
polygraphs are also used in research in other sciences. In PDD the polygraph
traditionally records physiologic activity with four sensors: blood pressure cuff,
electrodermal sensors, and two respiration sensors. Some instruments also
record finger pulse amplitude using a PPG.
See maintenance polygraph examination.
Complete graphical recording of physiological data from a polygraph test,
with the required annotations. Usually called a polygraph chart.
Positive Control Pair
The combination of the subjective truth question and the subjective lie
question, to form a set in the Positive Control Technique. See: Driscoll, Honts
& Jones (1987); Gordon & Cochetti (1982); Howland (1981); Reali (1978).
Positive Comparison Question
In the Positive Control Technique, each question is presented to the
examinee twice in a row, and the examinee is instructed to answer differently
the first time from the second time. Therefore, each question serves as its own
comparison question. See: Driscoll, Honts & Jones (1987); Gordon & Cochetti
(1982); Howland (1981); Reali (1978).
Positive Control Technique
Technique that employs most of the standard test questions except a
probable-lie comparison questions, and each question is presented twice in
succession during the testing. The examinee is instructed to answer truthfully
to the first presentation, and untruthfully the second time, or vice versa. While
the technique is amenable to the 7-position scoring, it has its own unique set
of decision rules that are different from the more familiar comparison question
formats. The Positive Control Technique is one form of the Yes-No Technique.
See: Driscoll, Honts & Jones (1987); Gordon & Cochetti (1982); Howland
(1981); Reali (1978).
Post-Conviction Sex Offender Testing (PCSOT)
Specialized application of polygraphy which aids in the management of
the convicted sex offender who has been released into the community, though
sometimes is employed as part of treatment of offenders who are incarcerated.
There are four principal types of PCSOT examinations: instant offense
examination, sexual history/disclosure examination, maintenance examination
and monitoring examination. See: Dutton (2000).
(L: after this) Establishment of criteria or analyses after the conduct of
the experiment is completed.
Final portion of a polygraph examination. The posttest could include a
debriefing of an examinee who passed the examination, or an interview or
interrogation of an examinee who failed the examination. The posttest may or
may not be a part of any given polygraph technique, and plays no part in the
formulation of the results in any polygraph technique.
Pre-ejection period (PEP)
Time between the Q wave of the electrocardiogram and the B wave of the
impedance cardiogram for the same pulse. It is the period between when
ventricular contraction occurs and the semilunar valves open ejecting blood
into the aorta. Shorter periods are thought to correlate very highly with
sympathetic nervous system arousal. The sensors for the production of the
PEP phenomenon are relatively noninvasive, and if future research validates it
as a diagnostic measure, the PEP could be added as an alternate PDD channel.
Preliminary Credibility Assessment Screening System (PCASS)
Device developed by the Johns Hopkins Applied Physics Laboratory, in
conjunction with the Lafayette Instrument company, at the request of the US
Government in 2005. Its concept of operation is to be used by minimally
trained US troops as an initial screening tool in war zones to pare down the
number of individuals who would undergo subsequent vetting by the polygraph
and other tools. It has two sensors: electrodermal and photoplethysmograph.
Test questions are typed into the template of the PDA platform, and the user
taps the screen to indicate the place of question onset. The PCASS is a onechart
test that runs about 12 minutes. At the completion of testing an
algorithm analyzes the data to produce the screening decision. Five laboratory
studies have been conducted with the PCASS using realistic wartime scenarios
or mock theft scenarios, with a combined accuracy of 80% when inconclusives
were excluded, and about 23% inconclusives. The algorithm was devised to
minimize false negatives. The PCASS was approved for use in the Department
of Defense in 2007. See: Battelle Memorial Institute (2007); Senter, Waller &
Premature Ventricle Contraction (PVC)
Term loosely applied to distortion in the cardiograph waveform resulting
from an ectopic heartbeat. More precisely it is a ventricular contraction
between two sinus cycles without a compensatory pause. Sometimes referred
to as extrasystolic beat (esb) in the older literature.
The earliest portion of the PDD examination process during which the
examinee and examiner discuss the test, test procedure, examinee’s medical
history, and the details of the test issues. The pretest interview also serves to
prepare the examinee for the testing. The length of the pretest interview ranges
from 30 minutes to 2 hours or longer, depending on the complexity of the case,
examiner-examinee interactions, and testing technique. All PDD techniques
use pretest interviews.
One of four tracks in the Quadri-Track Zone Comparison Technique,
which include the secondary, outside, and inside tracks. The primary track
contains a relevant question, and a non-current exclusive probable-lie
comparison question against which the relevant question is compared. See:
Likelihood of an occurrence, expressed as a number. By convention,
probabilities are reported in scientific reports as numbers between 0.00 and
1.00. Probabilities are most often reported in PDD studies to characterize the
likelihood of the experimental results occurring by chance.
Probable-Lie Comparison Question (PLC)
One of two major types of comparison questions. PLCs are questions to
which it is likely that the examinee is untruthful or unsure of his or her
answer. Their intended purpose is to create a competition of salience such that
the anxious innocent examinees will expend more of their physiologic
responses on them than the relevant questions, but the guilty examinee will
still find the relevant questions more arousing than the PLCs. Most systems of
analysis compare the physiological responses elicited by the PLC with those
from the relevant questions. A PLC is fundamentally different from a DLC
(directed lie) in that the examinee believes he must pass the PLC question to
pass the examination, whereas the true purpose of the DLC is more apparent
to the examinee. Two main types of PLCs are the exclusionary (Backster type)
and the non-exclusionary (Reid type).
Probation Polygraph Testing
Regularly scheduled or aperiodic PDD testing of offenders on probation
or parole, with the purpose of deterring repeat offenses. See maintenance
Probing Peak of Tension
See Searching Peak of Tension.
Those persons in a PDD experiment that play the role of either an
innocent examinee or guilty examinee. PDD examiners sometimes make the
mistake of referring to these examinees as programmed NDI (No Deception
Indicated) or programmed DI (Deception Indicated). NDI and DI are PDD
outcomes and not the examinees’ experimental assignments.
A test question so worded as to appear to be relevant to the examinee.
Example: “Did you lie to any question on this test?” or “Do you intend to
answer truthfully each question on this test?”
Psychogalvanic Reflex (PGR)
Expression coined by Veraguth for what is now called the electrodermal
response. See Veraguth (1906).
A term from the 1930s for the polygraph that consisted of the
pneumograph, sphygmograph, and a stimulus marker. Sometimes referred to
as the Berkeley Psychograph, the Lee Polygraph, and the cardio-pneumopsychograph.
In psychology, set is defined as a temporary orientation or state of
preparedness toward a particular stimulus or type of stimulus. Examples of
set include perceptual, motor, and neural sets. The expression psychological
set was introduced in PDD by Cleve Backster, who initially attributed it to a
psychological writer Floyd L. Ruch (Matte & Grove, 2001). Backster later
claimed to have made up the expression himself (Senter, Weatherman,
Krapohl, & Horvath (2010). Backster has made the concept central to his Zone
Comparison Technique and has tethered the concept to the emotion fear.
According to Backster’s PDD hypothesis, examinees are expected to attend
more to the category of question that presents the greater threat to their
interests, either the relevant or comparison questions. Subjects who are lying
to the relevant issues consider these questions more threatening than the
others, which, in turn, draw more attention to the relevant questions, and more
physiological arousal. Similarly, innocent subjects find the probable-lie
comparison questions more disconcerting, and the greater attention paid to
them generates the larger arousals. The expression psychological set, together
with its underlying assumptions, have long been questioned by scientists on
both sides of the polygraph debate, and there is not uniform agreement even
within the polygraph community that they are adequate. Nevertheless,
psychological set is an oft-cited expression for the differential responsivity
evoked by the Comparison Question Technique. Competing concepts include
“Differential Salience” (Senter, Weatherman, Krapohl & Horvath, 2010) and
“Relevant Issue Gravity” (Ginton, 2009.) See: Krapohl (2001); Matte & Grove
Psychological Stress Evaluator (PSE)
A voice stress device. Dektor Counterintelligence and Security and Allan
Bell Enterprises produced the PSE, first introduced in 1971. This device,
which is no longer manufactured, is the original voice stress analyzer. See:
Horvath (1978; 1979); Lynch & Henry (1979).
An individual with a personality marked with superficial charm, habitual
lying, no regard for others, showing no remorse after hurting others, having no
shame for outrageous and objectionable behavior, impulsivity, inability to form
relationships and take responsibility, failure to learn from punishment, lack of
empathy and conscience, and need for excitement. Also referred to as
antisocial personality. While popular lore holds that the psychopath, with his
diminished conscience, is able to defeat PDD testing, all research has found
that the guilty psychopath is no different from guilty non-psychopaths in being
detected by the polygraph. See: Barland & Raskin (1975); Raskin & Hare
(1978); Patrick & Iaconno (1989).
Psychophysiological detection of deception (PDD)
Common scientific term to denote the use of the polygraph to diagnose
Psychophysiological veracity (PV) examination
An alternative expression proposed by James Matte to describe the
process of making assessments of truthfulness or deception using a polygraph.
Matte offered the term as an alternate to polygraph examination and forensic
psychophysiological detection of deception examination. The expression has
not yet gained wide acceptance. See: Matte (1996).
The arithmetic difference between the systolic blood pressure and the
diastolic blood pressure.
Pulse Transit Time (PTT)
Period of time for the passage of a mechanical pulse wave between two
points on the body. PTT is used as a measure of sympathetic nervous system
arousal and may have some usefulness as a PDD parameter.
Pulse Wave Velocity
Propagation speed of a pressure pulse through the vascular system.
One of many cardiovascular measures being evaluated as a PDD diagnostic
One of several theories that attempt to explain PDD. It holds that
physiologic arousal during deception is activated by the fear of the
consequences if detected. This theory fails to explain why polygraph testing still
functions well in the absence of fear.
Change in the diameter of the pupil of the eye in response to stimuli.
Pupil size is regulated by the sphincter pupillae muscles in the iris, which
respond to parasympathetic stimulation, and the dilator pupillae muscles,
innervated by the sympathetic nervous system. Dilation can result from
sympathetic nervous system stimulation or the suppression of the
parasympathetic nervous system. Pupil dilation has been investigated by
several researchers as an index of stress, and continues to be a phenomenon of
interest in PDD. See: Bradley & Janisse (1981); Webb, Honts, Kircher,
Bernhardt & Cook (2009).
Purposeful Non-Cooperation (PNC)
An expression first reported by John Reid to denote a PDD outcome in
which examinees had used physical countermeasures in an attempt to defeat
the polygraph examination. Reid did not consider PNC to be synonymous with
the practicing of deception, though he wrote that it was a fairly reliable
indicator of the examinee’s motives to deceive.