Abstract
The response time (RT) based Concealed Knowledge Test (CKT) has been shown to accurately detect participants’ knowledge of mock-crime-related information. Tests based on ocular measures such as pupil-size and blink-rate have sometimes resulted in poor classification, or lacked detailed classification analyses. The present study examines the fitness of multiple pupil and blink related responses in the CKT paradigm. To maximize classification efficiency, participants’ concealed knowledge was assessed using both individual test measures and combinations of test measures. Results show that individual pupil-size, pupil-slope, and pre-response blink-rate measures produce efficient classifications. Combining pupil and blink measures yielded more accuracy classifications than individual ocular measures. Although RT-based tests proved efficient, combining RT with ocular measures had little incremental benefit. It is argued that covertly assessing ocular measures during RT-based tests may guard against effective countermeasure use in applied settings. A compound classification procedure was used to categorize individual participants and yielded high hit rates and low false-alarm rates without the need for adjustments between test paradigms and subject populations. We conclude that with appropriate test paradigms and classification analyses, ocular measures may prove as effective as other indices, though additional research is needed.
Highlights
COMBINING BLINK, PUPIL, AND RESPONSE TIME MEASURES IN A CONCEALED KNOWLEDGE TEST Researchers have developed several paradigms to assess whether or not participants are concealing sensitive information. This approach differs from the control questions “lie detector” test because it focuses on the ability of various dependent measures to indicate when participants recognize critical information as opposed to lying about it per se
Bivariate correlations were calculated between response time (RT) and various ocular measures; we found that only the RT and pupil-size measures were significantly correlated, r(30) = 0.65, p < 0.05
The primary goal of the present study was to examine whether RT and eye-based measures could be successfully used to detect concealed knowledge either alone or in combination
Summary
COMBINING BLINK, PUPIL, AND RESPONSE TIME MEASURES IN A CONCEALED KNOWLEDGE TEST Researchers have developed several paradigms to assess whether or not participants are concealing sensitive information (for reviews, see Ben-Shakhar and Furedy, 1990; Lykken, 1998; MacLaren, 2001; Ben-Shakhar and Elaad, 2003). This approach differs from the control questions “lie detector” test because it focuses on the ability of various dependent measures to indicate when participants recognize critical information as opposed to lying about it per se. Using evoked-related brain potentials (ERP) to index stimulus familiarity in the brain’s anterior cingulate cortex, Farwell and Donchin achieved a hit rate of 0.9 with no false-alarms
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