We quickly form first impressions about newly encountered people guiding our subsequent
behaviour (approach, avoidance). Such instant judgments might be innate and automatic,
being performed unconsciously and independently to other cognitive processes. Lying
detection might be subject to such a modular process. Unfortunately, numerous studies
highlighted problems with lying detection paradigms such as high error rates and learning
effects. Additionally, humans should be motivated doing both detecting others' lies and dis-
guising own lies. Disguising own lies might even be more challenging than detecting other
people's lies. Thus, when trying to disguise cheating behaviour, liars might display a mixture
of disguising (fake) trust cues and uncontrolled lying cues making the interpretation of the
expression difficult (perceivers are guessing). In two consecutive online studies, we tested
whether seeing an increasing amount (range 0-4) of lying cues (LC) and non-lying cues
(NLC) on a standard face results in enhanced guessing behaviour (studies 1 and 2) and
that enhanced guessing is accompanied by slower responding (study 2). Results showed
that pronounced guessing and slowest responding occurred for faces with an intermediate
number and not with the highest number of LC and NLC. In particular, LC were more impor-
tant than NLC to uncertain lying decisions. Thus, only a few LC may interfere with automatic
processing of lying detection (irrespective of NLC), probably because too little lying cue
information is yet available.