Investigating the Effectiveness of Polygraphs in Detecting Lies, Essay Example

Abstract

Polygraphs remain a popular way of credibility assessment in groups. The study aimed to explore the effectiveness of polygraph as lie detectors by comparing the effect of skeptical and positive framing on participants. The participants in the study were drawn from London (N=80). They were grouped with an equal number of partakers (- in two conditions of testing effectiveness of polygraphs- one group under positive framing (n=40) and a second group (n=40) under biased (negative framing). The participants (male=35%, female=65%) had an age range of 18-29. The two groups’ scores were statistically tested using two-way repeated-measures ANOVA (two-factor repeated-measures ANOVA / within-within-subjects ANOVA). The electrodermal activity (EDA) for each participant was determined based on polygraph readings. The results reveal a very strong interaction effect between the nature of framing (skeptical or positive) and EDA results.  It is concluded that the effectiveness of polygraph depends on the nature of framing. Polygraphs are susceptible to biases and may not be effective where participants are influenced to this that they are either effective or otherwise. It is necessary that stakeholders who rely on polygraphs in testing lies be informed of such limitations to take necessary precautions.

Keywords: Lie detector, polygraphs, EDA

Introduction

This study investigates the effectiveness of polygraphs as a lie detector under different framing circumstances.  It considers circumstances under which two groups of participants are exposed to positive and negative framing of polygraph’s effectiveness.  Polygraphs (commonly referred to as ‘lie detector’) refer to both devices and procedures that rely on a person’s physiological body responses when asked series of questions to test whether they are stating truths or lies.  The principle behind polygraphs is that there is an interaction between one’s honesty (or otherwise) and physiological indicators. When one says the truth, the physiological processes will be remarkably different from those exhibited when putting forth deceptive responses. Physiological indicators commonly relied upon to assess deception include pulse rate, respiration, blood pressure, respiration, and skin conductivity.  Several recent researches have been casting aspersions on the effectiveness of the polygraphs in detecting lies, with concerns over possible influences of framing and prior feedback of the previous users (Pelé et al., 2019).  While some scholars (such as O’Sullivan et al., 2009) find the device effective in lie detection, several past studies (Paul et al., 2020; Meijer & Verschuere, 2010) have revealed that the instrument is significantly ineffective in detecting lies. A recent study by Peleg et al. (2019) found that feedback to the participants in the previous instances of use will affect physiological arousal. They find that while polygraphs are effective in promoting honesty, feedback may compromise reliance on physical arousal, and by extension, the machine’s effectiveness in detecting lies.  Based on the past studies, it was hypothesized that participant physiological responses (and so lie detection) would be affected by skeptical and positive framing).  The study’s research question was: does framing of lie detector, either skeptically as effective (positive), affect polygraph test results?

Methods

Design. The study adopted a quasi-experimental design, in the form of independent measures where two groups of participants were used in two conditions of testing effectiveness of polygraphs- one group under positive framing (that it is effective) and a second group under biased (negative framing). There was further a control group who were not subjected to any briefing. The quasi-experimental design allowed objective assessment by allowing statistical comparison of the outcome from different groups of participants. The inclusion of the two experimental groups and the control group enhances the tests’ external reliability.

Participants. The participants were drawn from London (N=80) and were divided into two groups with an equal number of participants (n=40 in each group). The participants (male=35%, female=65%) had an age range of 18-29.

Procedure and materials. Polygraph equipment (psychophysiological equipment) measuring each participant’s psychophysiological activities was connected to each participant. The electrodermal activity (EDA) was then gathered. As a representation of autonomous nervous system responses, as an indication of psychophysiological responses. Higher EDA values indicate higher epidermal responses (for instance, higher sweating of the palm). The skeptical framing group was drawn from the class where validity and reliability of polygraphs had been taught, allowing a skeptical framing. For the positive framing group, professional-looking polygraph administrators were allowed to give a positive framing, indicating to the participants that it was a reliable tool for lie detection.

At the end of the test, the participants were informed that they were not professionally trained polygraph professionals, but just staff from another department. The study’s materials included polygraphs, colored pieces of paper, and structured questions to assess participant assessment of whether statements were lies or truths. All the participants completed ten similar sets of questions, to which they either lied or answered truthfully. They were directed to give 3-5 questions, and they would tell if they lied or told the truth towards the end of the test.  There was a control condition in which the participants were only showed colored paper, after which their EDA was measured.  From both the skeptical and the positive framing sessions, all data were analyzed by the study’s researcher.  The two groups’ scores were statistically tested using two-way repeated-measures ANOVA (two-factor repeated-measures ANOVA / within-within-subjects ANOVA), using SPSS version 21. Two-factor repeated ANOVA is a suitable statistical test for comparing statistical significance in the differences in the mean of the two groups in experiments with differences in two factors- conditions and time (Field, 2018; Howitt & Cramer, 2017).  There were differences in the participants’ conditioning in the present case regarding the framing of polygraph’s effectiveness (positive versus skeptical). The participants also participated at different timings, making two-factor repeated-measures ANOVA.  The test’s primary aim was to examine if there was an interaction between the two different factors (framing) as reflected in the dependent variables’ results (average EDA scores).

Results and Discussions

Descriptive Statistics

The descriptive statistics for the two groups of participants are presented in table 1.

Table 1: Descriptive Statistics for EDA results

Note: Results based on Two-factor repeated ANOVA output from primary data

As shown in the graph below, the estimated marginal means suggest a parallel line for the first two aspects of the pendent variables (lie and truth- as factors 1 and 2, respectively).

Figure 1: Estimated marginal mean for various independent variables

The parallel line indicates a lack of interaction between factors 1 (LIE) AND 2 (TRUTH). The lines are essentially diagonal, indicative of differences in the scores of the skeptical and positive framings. Nevertheless, the score (estimated marginal mean) for the positive and skeptical groups are different for both factors (Lie – skeptical mean=1.13 and SD=1.94, Positive mean 3.04, S.D.1.64; Truth-Skeptical mean= 0.94 and ds=1.85, positive mean=2.8 and SD=2.21). However, the line for closures (factor 3) is far from being parallel relative to the other two factors, a result that indicates the interactive effect with the other variables.  However, these are sample results and cannot be the basis for making conclusive inferences of the entire population. It is necessary to proceed with inferential tests to test the corresponding hypothesis.

Hypothesis Testing

The research aimed to evaluate the effectiveness of polygraph as lie detectors by comparing the effect of skeptical and positive framing on participants. Application of two-factor repeated measures ANOVA is necessary to evaluate the null hypothesis that their variances in the EDA scores are not significant for skeptical and positive framing. It is first necessary to evaluate if the core assumption for repeated measures ANOVA is met, and through extension, if some corrections are necessary. In this regard, we apply Mauchly’s test to test is the assumption of sphericity holds (table 2).

Table 2: Mauchly’s Test of Sphericity

In Mauchly’s test, sphericity holds when p > 0.05 (Field, 2018). The assumption is met by the data (p=.133, >0.05). As the assumption has been met, there is no need to undertake further corrections, for instance, through Greenhouse-Geisser of Huynh-Feldt. All the values to be used in subsequent hypothesis testing will be those of Sphericity Assumed.  Therefore, we can assess the tests of within-subjects effects results to assess if the interaction between different forms of framing and EDA results is significant. The interaction effect is evident from the results and is a strong one judging from the outcome (df= 2, 156, p=0.0000, <0.01). The results (table3) reject the null hypothesis, as p<0.01 (Sphericity Assumed).

Table 3: Tests of Within-Subjects Effects

It can be assumed that there is a similar trend of the interaction effect of positive and skeptical framing for both lie and truth, so it is justifiable to assume that the overall (main) effect is similar for these factors (it is justifiable to lump the effect together for all the factors.  Further multivariate tests, based on Wilks’ Lambda, equally show a strong interaction effect (DF=2, p<0.00), thereby rejecting the null hypothesis (TABLE 4). All the other tests of interactions (table 4) provide similar results, effectively affirming a strong interaction effect.

Table 4: Multivariate Tests for interaction effects

General Discussion and Conclusions

This was primarily concerned with assessing the effectiveness of polygraphs under varying framing circumstances-positive and skeptical.  Application of repeated measures ANOVA finds a strong interaction effect between the nature of framing (skeptical or positive) and EDA results.  Based on the results obtained from the study, it is evident that the polygraph’s effectiveness depends on the nature of framing.  It implies that polygraphs are susceptible to biases and may not be effective where participants are influenced to this that they are either effective or otherwise. The results put into aspersions the effectiveness of this critical tool (polygraphs), particularly for sensitive administrative and judicial services. These results further affirm the concerns raised in the vast body of extant literature (Kotsoglou, 2021; Meijer & Verschuere, 2010; Paul et al., 2020; Peleg et al., 2019) that participants’ prior knowledge and framing could compromise polygraphs effectiveness.  The ineffectiveness has been a major compromise to sensitive institutions, especially in the judicial and justice systems (Kotsoglou, 2021). It is necessary that stakeholders who rely on polygraphs in testing lies be informed of such limitations to take necessary precautions. An important precaution would be to avoid prejudicial remarks, cues, or framing (either positive or skeptical) regarding the polygraph’s effectiveness. Such cues will impact the outcome’s effectiveness and may not produce accurate answers due to possible interactions revealed in the study.

Despite efforts for a rigorous procedure and design, the present study remains limited by a few factors.  First, the sample size was relatively small (N=80), thereby subjecting the results to errors of probability. Secondly, there were limited polygraph values used in the results –namely EDA only. Other important parameters, including P.R. and R.R., have not been analyzed and need to be considered in future studies. Again, the study had limited demographic diversity in regards to age (no participant was aged 30 and above), geography (all participants from London), and possibly race or nationality (considering the experiment setting is essentially British).  Future studies should consider expanding the population size and target area to include larger samples (reducing probability errors). It will be equally important to consider wider or alternative geographical scope (beyond London) in selecting participants. The effectiveness of polygraphs among the excluded demographic groups (those aged 30 and above, for example) will enrich knowledge on whether age differences imply variation of interaction between framing and participant response. Some researchers (such as Collins, 2020) have also raised concerns over cont4estable ethical flaws of polygraphs, most notably racial prejudices. To limit undesirable racial biases, more experiments are necessary among the underrepresented (unrepresented) racial groups and nationalities

References

Collins, N. (2020). The Use of Polygraph Test in Clinical Forensic Psychiatry Settings. In Ethical Issues in Clinical Forensic Psychiatry (pp. 85-96). Springer, Cham.

Field, A.P. (2018). Discovering statistics using IBM SPSS statistics. Sage.

Howitt, D. & Cramer, D. (2017). Introduction to SPSS in Psychology (7th Ed.). Pearson.

Kotsoglou, K. N. (2021). Zombie forensics: the use of the polygraph and the criminal justice system’s integrity in England and Wales. The International Journal of Evidence & Proof, 25(1), 16-35.

Meijer, E. H., & Verschuere, B. (2010). The polygraph and the detection of deception.Journal of Forensic Psychology Practice, 10, 325–338

O’Sullivan, M., Frank, M. G., Hurley, C. M., & Tiwana, J. (2009). Police lie detection accuracy: the effect of life scenario. Law and Human Behavior, 33, 530–538.

Paul, B., Fischer, L., & Voigt, T. H. (2020). Anachronistic Progress? User Notions of Lie Detection in the Juridical Field. Engaging Science, Technology, and Society, 6, 328-346.

Peleg, D., Ayal, S., Ariely, D., & Hochman, G. (2019). The Lie Deflator-The effect of polygraph test feedback on subsequent (dis) honesty. Judgment & Decision Making, 16(6) 728–738. http://www.sjdm.org/journal/19/190526/jdm190526.pdf

Rosenfeld, J.P. (1995). Alternative Views of Bashore and Rapp’s (1993) alternatives to traditional polygraphy: a critique. Psychological Bulletin. 117, 159–66. doi:10.1037/0033-2909.117.1.159