Different Target Modalities Improve the Single Probe Protocol of the Response Time-Based Concealed Information Test

To detect if someone hides specific knowledge (called “probes”), the response time-based Concealed Information Test (RT-CIT) asks the examinee to classify items into two categories (targets/non-targets). Within the non-targets, slower RTs to the probes reveal recognition of concealed information. The preferred protocol examines one piece of information per test block (single probe protocol), but its validity is suboptimal. The aim of this study was to improve the validity of the single probe protocol by presenting the information in multiple modalities. In a preregistered study (N = 388) participants were instructed to try to hide their nationality. The items referring to the nationality were presented as words, flags, and maps. Increasing the number of modalities of the targets (BF₁₀ = 37), but not of the probes and irrelevants (BF₀₁ = 6), increased the CIT-effect.