1.0. Abstract
1.1. Aim
The aim of this report was to examine the effectiveness of a commonly used lie detector test; the “Guilty Knowledge test” (GKT). This research also aimed assess whether it should be considered a valid method of lie detection in different settings, such as the justice system.
1.2. Method
All participants engaged in the guilty knowledge test .Galvanic Skin Response (GSR) and Heart Rate (HR) of participants were measured for both control and experimental guilty knowledge questions. The sample was taken from the UCC undergraduate population. The research was a within-subjects, repeated measures design.
1.3. Results
It was found that the GKT is not an effective method of lie detection and no significant physiological differences were detected between the control and experimental conditions for HR. Differences were present between conditions for GSR. Limitations such as the ecological validity of the experiment were encountered.
1.4. Conclusion
Overall, it was concluded that the GKT is not an accurate or reliable method of detecting lies.
2.0. Introduction
2.1. Background
Forensic psychology involves the application of clinical psychology to forensic and legal settings (Cronin, 2013), and the concept of lie detecting has long fascinated scientists in this field. Lie detection was first explored by Italian physiologist Angelo Mosso in 1878. Masso was interested in the concept of how emotions elicit a physiological response and he studied blood circulation and breathing patterns; particularly how these changed under certain stimuli.
The idea that emotions elicit physiological responses laid the groundwork for subsequent study in the field. Modern lie detectors operate by taking physiological measures, two of which Galvanic Skin Response (GSR) and Heart Rate (HR). This research is interested in assessing the validity of lie detection based on these two physiological measures; whether the results provided are accurate, if it should be admissible in court and what implications this has. The “Guilty Knowledge Test” (GKT) operates using these physiological measures. This research will focus primarily on the efficacy of this particular test.
The GKT is a psychophysiological questioning technique often used in legal settings. Psychophysiology, according to Bernston and colleagues (2007) is the field of study which examines the “biological bases of cognitive, affective, social and developmental processes and behaviour”. The GKT can be used as part of a polygraph examination which aims to evaluate whether or not suspects have concealed information (Staunton and Hammond, 2011). It relies on measurement of heart rate (HR) and galvanic skin response (GSR).
2.3. Purpose of Study
The aim of this research is to examine if the GKT test produces valid results, and whether it is a reliable method of detecting lies. It is vital that research in this area is conducted due to its significant real-life implications. Lie detection has applications in settings such as the criminal justice system and is an invaluable tool if proved effective. It can be used alongside investigations to support evidence and serve justice to those guilty of crimes.
However, should the GKT be deemed ineffective, alternative methods of lie detection may be explored. It may also deter over-reliance on this method, encouraging deeper levels of critical analysis in the justice system and perhaps preventing false accusations and imprisonments. Due to the number of inconclusive studies on the GKT and its level of controversy, any additional research is critical and highly applicable.
2.4. Previous research and expected findings
Based on previous research, it is expected that this research will show that the GKT is not an effective method of detecting deception. Research such as that of Lykken (1959) show that GSR can be an effective way to detect lies however, these findings are challenged by other studies such as Furedy (1996) who declared the GKT completely unreliable. Overall, it is expected that this research will produce similar findings to that of Staunton and Hammond (2011) who declared GSR significant, but HR ineffective in detecting deceit.
3.0. Method
The aim of this study was to evaluate the efficacy of the guilty knowledge test in lie detecting.
3.1. Participants
Participants in the sample were recruited randomly on a volunteer basis from the UCC undergraduate population (N=71). Participants had mean age of 22 with standard deviation of 2. 27 males and 44 females participated in the study.
3.2. Research design
This study was a within subject, repeated measures design, which meant one sample served as both the experimental and control group. All participants carried out the guilty knowledge test and HR and GSR were measured in each participant for both the control and experimental questions. Each participant served as their own basis for comparison. This design method is most appropriate for the study because it eliminates the variables and differences that would exist if there were separate control and experimental groups. Having the entire sample participate in the mock crime and answer both control and experimental questions reduced the error variance associated with individual differences. This design ensures that the conditions are always exactly equivalent with respect to individual difference variables since the participants are the same in the different conditions.
3.3. Materials and measures
The two measures in the guilty knowledge test are galvanic skin response (GSR) and heart rate (HR). Each of these measures aim to detect lies by monitoring physiological activity. They operate on the concept that it takes more mental effort to lie than to tell the truth. This increased effort often results in stress and a detectable, accompanying physiological response. These responses are automatic, involuntary and out of the control of the participant. The measures were registered using a computerized polygraph system.
Galvanic skin response measures
Galvanic skin response is a measure of electro dermal activity in the skin (skin conductance). GSR of participants was measured using the constant-voltage method and the equipment used for this was a galvanic skin response monitor. This operates by measuring the electrical conductance of the skin while the participant answers questions. When an individual is aroused, the moisture levels in the skin are altered causing its electrical conductance to change (Dawson, Schell, & Filion, 2007) .According to research by Lykken and Venables (1971), this is due to sweat glands which are controlled by the sympathetic nervous system, and this change in conductance can be an indirect measure of mental activity. It is hypothesised that the change in GSR indicates that the participant has answered dishonestly.
Heart rate measures
This measure operates on the same principle that mental activity elicits a physiological response. Cardiovascular activity was monitored using polygraph equipment as guilty knowledge questions are answered. Concealing a truth requires more conscious effort that being truthful, and thus leads to Physiological changes such as increased heart rate. In this way, a measurement of heart rate can be used to indicate whether or not the participant may be withholding information.
3.4. Procedure
The procedure for this research involved each participant in the sample engaging in a mock crime, wherein they were instructed to “steal” a sum of money from a specified location. Every participant was then asked to respond to a set of questions; the guilty knowledge test, while denying involvement in the mock crime. The questions used as part of the guilty knowledge test were a mixture of questions in which the participant could comfortably answer honestly, such as their name, and questions about the crime which were intended to elicit a stress response. HR and GSR were recorded for every participant as they answered the questions.
3.5. Data analysis
The data collected on GSR and HR from each participant was analysed using IBM SPSS statistical software. Paired sample t-tests were the statistical analyses used to examine and interpret the data. This analysis was most appropriate because it was a repeated measures design and this test allows us to compare the measures taken in each condition against one another. It is a useful analysis as it helps us recognize whether any significant changes occurred between measures, and if engagement in the mock crime lead to a distinct and detectable stress response in participants. Overall, this analysis will help to indicate whether the guilty knowledge test can be considered scientifically valid.
3.6. Ethics
Ethical concerns regarding the emotional wellbeing of the individual being interrogated have often been raised. The nature of the questions and interrogative setting of the guilty knowledge test and indeed, other lie detection tests, may elicit false confessions from the individual. John Furedy (1993) explored this ethical concern along with others which he labelled “polygrapher's dilemma”. Furedy recognised that the classifying of innocent individuals as “deceptive” can damage their psychological wellbeing. It is also a concern that individuals, particularly those who are innocent, are not debriefed regarding any feelings of unease about issues raised in the test