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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.

According to the adaptive memory perspective, memory should function more efficiently in fitness-relevant domains. The current work explored whether there is a mnemonic tuning in a fundamental domain for human evolution: reproduction. In two experiments, female participants assessed how desirable potential male candidates (represented by a face and a short descriptor) would be in the context of a long-term mating relationship or in the context of a long-term work relationship. Then, after a short distractor task, participants performed a recognition task for the faces and a source memory task. Finally, they were asked to recall the descriptors presented during encoding. Experiment 1 used a between-subjects design, whereas Experiment 2 employed a within-subject design. In both experiments, participants remembered the faces best when they were encoded in the mating condition. Also, in Experiment 1, source memory performance was better in the mating condition than in the working condition with the reverse being true for free recall of the descriptors. The latter difference was not observed in Experiment 2. These results suggest a potential mnemonic tuning for the faces of potential mate partners.

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A long-standing goal shared by researchers has been to design optimal experimental procedures, including the selection of appropriate stimuli. Pictures are commonly used in different research fields. However, until recently, researchers have relied mostly on line-drawings, which can have poor ecological validity. We developed a set of high quality standardized photographs of objects from six different categories, recorded under two camera viewpoints, and five presentation conditions (on its own, held by clean hands, and by hands covered with different substances: sauce, chocolate and mud). These various staging conditions can be used to induce different emotional states while maintaining the object of interest constant. We first report normative data on the objects’ name agreement and familiarity collected from North American and Portuguese participants. Results showed high name agreement and familiarity in both samples. Next, arousal, disgust and valence ratings were collected for the stimuli under either an emotional-activating or a neutral context. Subjective ratings varied according to the staging condition and the context, confirming that the same items can effectively be used in different emotional conditions. This database allows researchers to select more ecologically-valid stimuli according to their research purposes while considering several variables of interest and avoiding item-selection problems commonly present when comparing responses to neutral and emotional items.

Facial attractiveness (FA) impacts various aspects of human life making it widely studied. This study presents attractiveness norms for a set of 223 neutral faces of young adults collected both online and in the laboratory. Furthermore, data are presented according to variables known to influence attractiveness judgments: sex, sexual orientation, age, and relationship status of the respondent. Finally, our data can be used to study FA across cultures and is possibly useful to researchers studying FA in other cultures. The potential impact of these norms is as large as the variety of domains in which attractiveness is relevant.

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