The role of similarity in deductive categorical inference

The category inclusion rule specifies that categories inherit the properties of their superordinates. For example, given thatall metals are pentavalent, it can be concluded thatall iron is pentavalent. Sloman (1998) showed that people do not fully endorse conclusions that follow from the category inclusion rule. He claims that people rely on the similarity between the premise and the conclusion categories (metals andiron), rather than applying the category inclusion rule. By allowing reasoners to rate their certainty for category relations (e.g.,iron is metal), as well as for conclusions, the present study shows that similarity has only an indirect effect on the certainty of conclusions: Reasoners are more certain that similar categories have a category inclusion relation, and this in turn affects the certainty of conclusions based on this relation.     

Chimpanzee (Pan troglodytes) intentional communication is not contingent upon food

Studies of great apes have revealed that they use manual gestures and other signals to communicate about distal objects. There is also evidence that chimpanzees modify the types of communicative signals they use depending on the attentional state of a human communicative partner. The majority of previous studies have involved chimpanzees requesting food items from a human experimenter. Here, these same communicative behaviors are reported in chimpanzees requesting a tool from a human observer. In this study, captive chimpanzees were found to gesture, vocalize, and display more often when the experimenter had a tool than when she did not. It was also found that chimpanzees responded differentially based on the attentional state of a human experimenter, and when given the wrong tool persisted in their communicative efforts. Implications for the referential and intentional nature of chimpanzee communicative signaling are discussed.     

Reaction in action: intergroup contrast in automatic behavior

Whereas previous research has shown automatic behavior conforming to outgroup stereotypes, the authors demonstrate automatic behavioral contrast away from a stereotype/trait associated with an outgroup (Study 1 and 2) and point to the importance of an "us-them" intergroup comparison in this process. In Study 1, participants colored pictures more messily when neatness was associated with an outgroup rather than the ingroup. In Study 2, using a different behavior, participants primed with busy business people reacted faster than controls (assimilation) but became slower when their student ingroup identity was activated (contrast). Subliminally priming an "us-them" intergroup comparison set undermined the accessibility of outgroup stereotypic words (Study 3), especially for those higher in prejudice (Study 4). This suggests that people automatically distance themselves from outgroup attributes when intergroup antagonism is cued or chronic. Implications for the role of self and comparison processes in automatic behavior are discussed.     

Poor recall of eye-movement signals from Stage 2 compared to REM sleep: implications for models of dreaming

An ongoing assumption made by sleep researchers is that since dreams are more often recalled on awakening from rapid eye movement (REM) sleep, dreams must occur more often during this stage of sleep. An alternative hypothesis is that cognition occurs throughout sleep, but the recall of this mentation differs on awakening. When a dream is not reported on awakening, there is no method of establishing whether it did not happen or was forgotten. The aim of the present study was to investigate this issue using an eye movement (EM) signal verification technique. Participants were instructed to produce an EM signal whenever they heard a tone. Tones were presented at increasing volume during Stage 2 and REM sleep until EM signal verification was observed. Ninety seconds after signal verification, participants were awakened and asked if they remembered hearing the tone or responding with the EM signal. Such recollection of signal verified tone (SVT) presentations was significantly less after Stage 2 sleep (65%) compared to REM sleep (100%) presentations. Furthermore, SVT recall was significantly correlated with reported dream recall frequency, suggesting the same processes involved in recalling SVTs might also underlie dream recall.     

How do memory systems interact? Evidence from human classification learning

Studies of human classification learning using functional neuroimaging have suggested that basal ganglia and medial temporal lobe memory systems may interact during learning. We review these results and outline a set of possible mechanisms for such interactions. Effective connectivity analyses suggest that interaction between basal ganglia and medial temporal lobe are mediated by prefrontal cortex rather than by direct connectivity between regions. A review of possible neurobiological mechanisms suggests that interactions may be driven by neuromodulatory systems in addition to mediation by interaction of inputs to prefrontal cortical neurons. These results suggest that memory system interactions may reflect multiple mechanisms that combine to optimize behavior based on experience.     

Put your money where your mouth is! Explaining collective action tendencies through group-based anger and group efficacy

Insights from appraisal theories of emotion are used to integrate elements of theories on collective action. Three experiments with disadvantaged groups systematically manipulated procedural fairness (Study 1), emotional social support (Study 2), and instrumental social support (Study 3) to examine their effects on collective action tendencies through group-based anger and group efficacy. Results of structural equation modeling showed that procedural fairness and emotional social support affected the group-based anger pathway (reflecting emotion-focused coping), whereas instrumental social support affected the group efficacy pathway (reflecting problem-focused coping), constituting 2 distinct pathways to collective action tendencies. Analyses of the means suggest that collective action tendencies become stronger the more fellow group members "put their money where their mouth is." The authors discuss how their dual pathway model integrates and extends elements of current approaches to collective action.     

Attitude formation through exploration: valence asymmetries

The formation of attitudes toward novel objects was examined as a function of exploratory behavior. An initial experiment, in which participants played a computer game that required them to learn which stimuli, when sampled, produced favorable or unfavorable outcomes, demonstrated learning, attitude formation, and generalization to novel objects. The findings also revealed 2 interesting valence asymmetries: a learning asymmetry involving better learning for negatively valenced than positively valenced objects and a generalization asymmetry involving stronger generalization as a function of negative than of positive attitudes. Findings from 4 experiments led to an explanation of the learning asymmetry in terms of information gain being contingent on approach behavior and related the generalization asymmetry to a negativity bias that weighs resemblance to a known negative more heavily than resemblance to a positive.     

An MMPI-2 scale to identify reported history of emotional abuse

A 42-item MMPI-2 scale classified 97.5% of 201 clinic outpatients into groups reporting or not reporting prior emotional abuse.     

Task-effector asymmetries in a rhythmic continuation task

Variability in rhythmic movements has been interpreted as a signature of internal or peripheral noise processes. Grounded in an oscillator interpretation, this study hypothesized that period variability and drift arises from the asymmetry between target period and the limb's intrinsic dynamics. Participants synchronized to 7 target periods, swinging 1 of 3 pendulums in a continuation paradigm; 3 periods were longer, 3 shorter, and 1 identical to the preferred period. Results supported 5 predictions: Drift toward the preferred period was observed that scaled with the asymmetry. Variability was lowest for symmetry conditions and increased with the asymmetry. Variability decreased concomitant with the approach toward the preferred period. Periods exponentially approached the preferred period with positive autocorrelations up to 10 cycles.