Testing for social learning and imitation in common marmosets, <Emphasis Type="Italic">Callithrix jacchus</Emphasis>, using an artificial fruit

We tested for social learning and imitation in common marmosets using an artificial foraging task and trained conspecific demonstrators. We trained a demonstrator marmoset to open an artificial fruit, providing a full demonstration of the task to be learned. Another marmoset provided a partial demonstration, controlling for stimulus enhancement effects, by eating food from the outside of the apparatus. We thus compared three observer groups, each consisting of four animals: those that received the full demonstration, those that received the partial demonstration, and a control group that saw no demonstration prior to testing. Although none of the observer marmosets succeeded in opening the artificial fruit during the test periods, there were clear effects of demonstration type. Those that saw the full demonstration manipulated the apparatus more overall, whereas those from the control group manipulated it the least of the three groups. Those from the full-demonstration group also contacted the particular parts of the artificial fruit that they had seen touched (localised stimulus enhancement) to a greater extent than the other two groups. There was also an interaction between the number of hand and mouth touches made to the artificial fruit for the full- and partial-demonstration groups. Whether or not these data represent evidence for imitation is discussed. We also propose that the clear differences between the groups suggest that social learning mechanisms provide real benefits to these animals in terms of developing novel food-processing skills analogous to the one presented here.     

Valence focus and the perception of facial affect

Individuals differ in the extent to which they emphasize feelings of pleasure or displeasure in their verbal reports of emotional experience, an individual difference termed valence focus (VF). This multimethod study indicates that VF is linked to heightened efficiency in perceptual processing of affective stimuli. Individuals higher in VF (i.e., who emphasized feelings of pleasure/displeasure in reports of emotional experiences) were more sensitive to changes in negative facial expressions than individuals lower in VF. The effect was not accounted for by current affective state or other personality characteristics. Implications for the validity of self-reported experienced emotion are discussed.     

Detection of change in shape: an advantage for concavities

Shape representation was studied using a change detection task. Observers viewed two individual shapes in succession, either identical or one a slightly altered version of the other, and reported whether they detected a change. We found a dramatic advantage for concave compared to convex changes of equal magnitude. Observers were more accurate when a concavity along the contour was introduced, or removed, compared to a convexity. This result sheds light on the underlying representation of visual shape, and in particular the central role played by part-boundaries. Moreover, this finding shows how change detection methodology can serve as a useful tool in studying the specific form of visual representations.     

Test modality affects source monitoring and event-related potentials

Two experiments investigated the effect of test modality (visual or auditory) on source memory and event-related potentials (ERPs). Test modality influenced source monitoring such that source memory was better when the source and test modalities were congruent. Test modality had less of an influence when alternative information (i.e., cognitive operations) could be used to inform source judgments in Experiment 2. Test modality also affected ERP activity. Variation in parietal ERPs suggested that this activity reflects activation of sensory information, which can be attenuated when the sensory information is misleading. Changes in frontal ERPs support the hypothesis that frontal systems are used to evaluate source-specifying information present in the memory trace.     

Introduction to the special section on structural equation modeling

Structural equation modeling (SEM) is a frequently used data-analytic technique in psychopathology research. This popularity is due to the unique capabilities and broad applicability of SEM and to recent advances in model and software development. Unfortunately, the popularity and accessibility of SEM is matched by its complexities and ambiguities. Thus, users are often faced with difficult decisions regarding a variety of issues. This special section is designed to increase the effective use of SEM by reviewing recently developed modeling capabilities, identifying common problems in application, and recommending appropriate strategies for analysis and evaluation.     

Axis I and axis II disorders as predictors of prospective suicide attempts: findings from the collaborative longitudinal personality disorders study

This study examined diagnostic predictors of prospectively observed suicide attempts in a personality disorder (PD) sample. During 2 years of follow-up, 58 participants (9%) reported at least 1 definitive suicide attempt. Predictors that were examined include 4 PD diagnoses and selected Axis I diagnoses (baseline and course). Multivariate logistic regression analyses indicated that baseline borderline personality disorder (BPD) and drug use disorders significantly predicted prospective suicide attempts. Controlling for baseline BPD diagnosis, proportional hazards analyses showed that worsening in the course of major depressive disorder (MDD) and of substance use disorders in the month preceding the attempt were also significant predictors. Therefore, among individuals diagnosed with PDs. exacerbation of Axis I conditions, particularly MDD and substance use, heightens risk for a suicide attempt.     

Investigating the encoding and retrieval of intentions with event-related potentials

Strong evidence exists in the literature that remembering to complete intentions involves executive processing subserved by the frontal lobes. Event-related potentials were measured during the encoding of actions with the intention to perform versus more neutral material about which there was no such intentionality. Event-related potentials were also measured in a two-alternative discrimination task requiring identification of the to-be-performed actions and to-be-memorized actions. The results suggest that formation and retrieval of intentions differs from encoding and retrieval of similar material committed to memory. Additionally, the results suggest that right frontal areas may play an important role in the formation of prospective actions and that intentions are kept active in memory by processing mediated by the left frontal pole.