In primates living in one-male groups, the sole resident male is often an important social partner for group immatures. For such groups, however, replacement of the male and subsequent disruptions of their relationships are almost inevitable. Here, we described social relationships of immature wild western lowland gorillas within a habituated group, where two natal and eight immigrant immatures lived with the resident silverback. We recorded 5 m proximities among group members as an indicator of social closeness. We found that natal immatures spent more time within 5 m of the silverback than immigrant ones. The social closeness between the silverback and the younger immigrant immatures sharply increased after 1 year, but these values were still below those of the natal immatures. Regarding the development of independence from the mother, we found no significant difference between natal and immigrant immatures. The socially preferred nonmother mature for natal immatures was the silverback, whereas many immigrant immatures preferred a paternal adult sister who had previously co-resided with them in a previous group. Our results suggest that familiarity may be an important determinant of the social closeness between the silverback and immatures, but 1 year of co-residence might be too short to construct sufficient familiarity. The paternal sister may have played a pivotal role in the assimilation of immigrant immatures into the non-natal group. Nonetheless, it is not negligible that the silverback and immigrant immatures formed day-to-day close proximities. His tolerance toward co-residence with immigrant immatures can be considered a reproductive tactic.

Classification performance is better for learned than unlearned stimuli. This was also reported for faces, where identity matching of unfamiliar faces is worse than for familiar faces. This familiarity advantage led to the conclusion that variability across appearances of the same identity is partly idiosyncratic and cannot be generalized from familiar to unfamiliar identities. Recent advances in machine vision challenge this claim by showing that the performance for untrained (unfamiliar) identities reached the level of trained identities as the number of identities that the algorithm is trained with increases. We therefore asked whether humans who reportedly can identify a vast number of identities, such as super recognizers, may close the gap between familiar and unfamiliar face classification. Consistent with this prediction, super recognizers classified unfamiliar faces just as well as typical participants who are familiar with the same faces, on a task that generates a sizable familiarity effect in controls. Additionally, prosopagnosics\' performance for familiar faces was as bad as that of typical participants who were unfamiliar with the same faces, indicating that they struggle to learn even identity-specific information. Overall, these findings demonstrate that by studying the extreme ends of a system\'s ability we can gain novel insights into its actual capabilities.

Reciprocity is one of the most prominent explanations for the evolution of stable cooperation. Although reciprocity has been studied for decades in numerous animal species and behavioural contexts, its underlying proximate mechanisms remain unclear. Domestic dogs provide a useful model species for the study of proximate mechanisms, though there are currently inconsistent findings regarding dogs\' propensity to reciprocate. Here, we investigated whether, after minimal training, pet dogs would press a button, which remotely controlled a food dispenser, to deliver food to an enclosure occupied by a helpful conspecific that had provided them with food or an unhelpful conspecific that had not provided them with food. We included an asocial control condition in which the enclosure was unoccupied and a social facilitation control in which the food delivery mechanism was non-functional. Whether subjects were familiar with the helpful and unhelpful conspecifics was also varied. In addition, to investigate potential mechanisms underlying reciprocity, we measured subjects salivary oxytocin concentration before and after they experienced the helpful and unhelpful acts. There was no effect of the previous helpfulness or the familiarity of the partner on the number of times subjects pressed the button. However, there was also no effect of the presence of a partner or the operationality of the food delivery mechanism on the number of button presses, indicating that subjects were not pressing the button to provision the partner. Moreover, the experience of the helpful or unhelpful act did not influence subjects\' salivary oxytocin concentration. Variation in findings of reciprocity across studies appears to correspond with differing training protocols. Subjects\' understanding of the task in the current study may have been constrained by the limited training received. Additional tests to verify subjects\' understanding of such tasks are warranted in future studies.

This paper introduces A Library for Innovative Category Exemplars (ALICE) database, a resource that enhances research efficiency in cognitive and developmental studies by providing printable 3D objects representing 30 novel categories. Our research consists of three experiments to validate the novelty and complexity of the objects in ALICE. Experiment 1 assessed the novelty of objects through adult participants\' subjective familiarity ratings and agreement on object naming and descriptions. The results confirm the general novelty of the objects. Experiment 2 employed multidimensional scaling (MDS) to analyze perceived similarities between objects, revealing a three-dimensional structure based solely on shape, indicative of their complexity. Experiment 3 used two clustering techniques to categorize objects: k-means clustering for creating nonoverlapping global categories, and hierarchical clustering for allowing global categories that overlap and have a hierarchical structure. Through stability tests, we verified the robustness of each clustering method and observed a moderate to good consensus between them, affirming the strength of our dual approach in effectively and accurately delineating meaningful object categories. By offering easy access to customizable novel stimuli, ALICE provides a practical solution to the challenges of creating novel physical objects for experimental purposes.

Episodic memory is accounted for with two processes: \'familiarity\' when generally recognizing an item and \'recollection\' when retrieving the full contextual details bound with the item. Paradoxically, people sometimes report contextual information as familiar but without recollecting details, which is not easily accounted for by existing theories. We tested a combination of item recognition confidence and source memory, focusing upon \'item-only hits with source unknown\' (\'item familiarity\'), \'low-confidence hits with correct source memory\' (\'context familiarity\'), and \'high-confidence hits with correct source memory\' (\'recollection\'). Results across multiple within-subjects (trial-wise) and between subjects (individual variability) levels indicated these were behaviorally and physiologically distinct. Behaviorally, a crossover interaction was evident in response times, with context familiarity being slower than each condition during item recognition, but faster during source memory. Electrophysiologically, a Condition x Time x Location triple dissociation was evident in event-related potentials (ERPs), which was then independently replicated. Context familiarity exhibited an independent negative central effect from 800-1200 ms, differentiated from positive ERPs for item-familiarity (400 to 600 ms) and recollection (600 to 900 ms). These three conditions thus reflect mutually exclusive, fundamentally different processes of episodic memory. Context familiarity is a third distinct process of episodic memory.

Nonsensical information increases task novelty, which makes it difficult to rely on previous learning and provides insight into the learning of new tasks. This study investigated procedural-based action scripts in everyday memory for meal preparation tasks in virtual reality. The sample (N = 171) consisted of 3 groups determined by age and cognitive function: young adults (YA; n = 61), older adults with normal cognition (OA; n = 82), and older adults with impaired cognition (IC; n = 28). The three groups completed the Virtual Kitchen Protocol, a virtual reality-based measure of learning and memory for cooking both familiar and nonsensical meals. Results showed that YAs had a greater recall for both familiar and nonsensical meals than OAs or ICs. Additionally, novel stimuli (i.e., nonsensical meal tasks) appear to impact older adults more than young adults. Among older adults, impaired cognition was associated with lower performance on both the sensical and nonsensical meals compared to normal cognition. All three groups performed better on familiar tasks than nonsensical tasks. These results were consistent with the notion that familiarity may be of greater use than novelty in the context of procedural-based action scripts.

Background: Effective healthcare clinician communication is a key component of quality palliative and end-of-life (PEOL) care. However, communication may be hampered when clinicians are not comfortable initiating these conversations with patients and their families. Clinicians working in rural areas report several barriers to providing palliative care. This study examined the relationship between rural and urban clinicians\' reported familiarity with their patients and families end-of-life, their reported comfort in initiating PEOL conversations, and their PEOL care knowledge. Method: This study used a cross-sectional design to examine the relationships between rural and urban clinicians\' familiarity, their comfort in PEOL communication, and their PEOL care knowledge. Results: N = 548 rural and urban clinicians participated. Rural clinicians reported greater familiarity, more PEOL knowledge, and more comfort with PEOL communication. Multiple regression analyses of PEOL knowledge showed significant associations in knowledge with older clinicians (P < 0.01) and additional palliative care training (P < 0.01); comfort in PEOL communication had significant associations with more palliative care training (P < 0.01) and opportunities to provide palliative care (P < 0.01). Conclusion: The concept of familiarity is highly complex and poorly understood in relation to PEOL care in both rural and urban settings. Future research is needed to explore how additional training in PEOL care and clinician reported familiarity positively impact patient outcomes by increasing the number of advance directives completed and followed and improved documentation of advance care planning.

Across different epochs and societies, humans occasionally gather to jointly make music. This universal form of collective behavior is as fascinating as it is fragmentedly understood. As the interest in joint music making (JMM) rapidly grows, we review the state-of-the-art of this emerging science, blending behavioral, neural, and computational contributions. We present a conceptual framework synthesizing research on JMM within four components. The framework is centered upon interpersonal coordination, a crucial requirement for JMM. The other components imply the influence of individuals\' (past) experience, (current) social factors, and (future) goals on real-time coordination. Our aim is to promote the development of JMM research by organizing existing work, inspiring new questions, and fostering accessibility for researchers belonging to other research communities.

Vivid episodic memories in humans have been described as the replay of the flow of past events in sequential order. Recently, Panoz-Brown et al. Current Biology, 28, 1628-1634, (2018) developed an olfactory memory task in which rats were presented with a list of trial-unique odors in an encoding context; next, in a distinctive memory assessment context, the rats were rewarded for choosing the second to last item from the list while avoiding other items from the list. In a different memory assessment context, the fourth to last item was rewarded. According to the episodic memory replay hypothesis, the rat remembers the list items and searches these items to find the item at the targeted locations in the list. However, events presented sequentially differ in memory trace strength, allowing a rat to use the relative familiarity of the memory traces, instead of episodic memory replay, to solve the task. Here, we directly manipulated memory trace strength by manipulating the odor intensity of target odors in both the list presentation and memory assessment. The rats relied on episodic memory replay to solve the memory assessment in conditions in which reliance on memory trace strength is ruled out. We conclude that rats are able to replay episodic memories.

This work focused on the perception of the food healthiness of in-flight meals. This work adopts presentation as the determinant. This work also employs attitude as the consequence of food healthiness. This research also examines the moderating effect of familiarity on the relationship between food presentation and food healthiness. This research used a survey, and survey participants were recruited via a Clickworker platform service. Survey participants were experienced with in-flight meals. The number of observations was 317. Moreover, this research tested the research hypotheses using the Hayes process macro Model 7. The results revealed that food healthiness is positively influenced by presentation and that food healthiness positively affects attitude. Moreover, the results revealed that the type of presentation has a positive influence on attitude. Familiarity was a significant moderating variable for the relationship between food presentation and food healthiness. This work sheds light on the literature by identifying the associations among four attributes of in-flight meals. Additionally, the results of this study could be used as a reference to develop better in-flight meals.