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Signal Inversion: The Systematic Miscalibration of Deception Detection and Its Implications for Justice System Design

A. C. Applebee, L. N. Combe · 2026

Abstract

This paper presents converging evidence for the Signal Inversion Effect: a systematic pattern whereby authentic cognitive and linguistic behaviours associated with truthfulness are misidentified as indicators of deception by human observers. Across four studies we find: (1) disfluency is significantly higher in truthful trial testimony than deceptive testimony (d = 0.60, p = .004), a medium effect 6× larger than the median deception cue; (2) false confessions show massive linguistic distancing, with impersonal pronoun contractions up to 12× higher and second-person references 7.6× higher than true confessions; (3) 91.3% of publicly believed deception cues are empirically unrelated or inversely related to actual deception (21/23 cues inverted; binomial test p < .0001; weighted inversion index = 0.81); and (4) human deception detection averages 54% accuracy (lie detection specifically: 47%, below chance), while algorithmic classification using linguistic features achieves 63.5–83%. Demeanour-based credibility assessment does not merely fail to detect deception — it systematically penalises truthful speakers whose authentic cognitive effort produces the signals misread as guilt.

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