PSY2215 The Psychologist’s Toolkit: Advanced Quantitative Techniques Assessment 2026

PSY2215 Assessment: Quantitative Lab Report

A group of researchers at a north London institution were interested how effective the polygraph is at detecting lies. They also wanted to know whether the framing of the effectiveness of the polygraph (as a lie-detector) influenced its actual effectiveness – was the polygraph only effective as a lie-detector when participants were led to believe it was effective?

Each participant was connected to psychophysiological equipment measuring heart rate (HR), electrodermal activity (EDA), and respiratory rate (RR). For this analysis, only EDA will be included as a representative measure of the autonomic nervous system activity, where a higher positive value represents higher levels of EDA, taken as a measure of more arousal. In other words, the higher the EDA value, the more your palms sweat.

Each participant completed the same set of tasks. They were asked a series of ten questions and they either answered truthfully or they lied. They were instructed to give an untruthful answer on 3-5 of the ten questions (whether they told the truth or not was verified once the testing session was over). Participants also engaged in a control condition where they were presented with coloured pieces of paper. They simply looked at the paper which was presented for ten seconds in front of them. The average EDA activity was then calculated for each participant when they lied, told the truth, and were shown coloured paper.

The study consisted of two different groups, with 40 participants in each group. The age range of participants was 18-29 years, with 65% female.

One group performed the polygraph testing session as part of their laboratory class where a sceptical view of the effectiveness of the polygraph as lie detector was taught.

Participants in the second group were invited to take part in an experiment in return for course credits (the nature of the experiment was unknown to the participant). The testing session was conducted by two professional looking polygraph administrators and the polygraph was positively described as a reliable and valid method for detecting lies. The participant was told only at debriefing (after the study) that the two polygraph testers were not actually trained professionals but instead two members of staff from another department.

All data, from both the sceptical and the positive framing sessions, was analysed by one person (the researcher of the study).

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