The Mnemonic Tuning for Contamination: A Replication and Extension Study Using More Ecologically Valid Stimuli.

To face threats posed by pathogens, natural selection designed the Behavioral Immune System, which orchestrates several responses aimed to prevent contact with pathogens. Memory seems to augment this system. Using line drawings of objects, previous studies found that objects described as having been touched by sick people were better remembered than those described as having been touched by healthy people. The current work was designed to replicate and extend these initial studies using more ecologically-valid stimuli-photographs of real objects being held by hands. These photographs were shown along with descriptors (Experiment 1a) or faces (Experiment 1b) denoting the health status of the person whose hands were holding the objects. Experiments 2 and 3 used, as cues of contamination, dirty hands covered with a substance described as being vomit and diarrhea, respectively. Experiment 3 also investigated the need for a fitness-relevant context for the mnemonic effect to occur. In all experiments, stimuli were presented individually on the screen with the "contamination cue." During encoding participants had to identify whether each object had been touched by a sick or a healthy person. The results of the final surprise free recall tasks replicated those previously reported: performance was enhanced for objects encoded as potential sources of contamination. Furthermore, the results of the last study reinstate the importance of fitness-relevance for the effect to occur. These results establish the generality of the contamination effect previously found, now using more ecologically-valid stimuli.