Abstract

The cognitive theory of lie detection suggests that it takes longer on average to formulate a deliberately false
response than a truthful one because it requires the truth to first be known and then altered, adding an extra
component to the response process. This concept was upheld in a modified form in three experiments where
subjects indicated as quickly as possible whether presented numbers were higher or lower than a given standard
number, and to “lie” (give the wrong answer deliberately) on half the trials. Results suggested that lying adds a
constant additional time to reaction times (RTs) independently of other factors such as the complexity of the
cognitive task or method of response. Additionally, true Yes RTs were shorter than true No ones, producing an
interaction with the lying constant such that RTs could reliably distinguish truth from lies for Yes responses but
not so easily for No responses.

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