Is a picture worth a thousand words? Congruency between encoding and testing improves detection of concealed memories

The current study addressed modality effects in a web-based Concealed Information Test (CIT) by asking participants to encode, and later conceal, crime-related details. Items were encoded and tested verbally or pictorially. A pilot (N = 73) and a preregistered study (N = 158) showed a robust interaction between encoding and testing modality: Items that were encoded and tested in the same modality were associated with better detection. Moreover, recognition of verbally encoded items could not be detected in a pictorial test. Our findings support the existence of a modality-congruency effect when subjects try to conceal their knowledge. In applied scenarios, the modality of test items should be matched to the modality in which crime-related details were encoded. Furthermore, a pictorial CIT might protect informed innocents if leakage happened verbally.