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The ability to associate memorized objects with their location in space gradually declines during normal aging and can drastically be affected by neurodegenerative diseases. This study investigates object-location paired-associates learning (PAL) in the grey mouse lemur ( Microcebus murinus ), a nonhuman primate model of brain aging. Touchscreen-based testing of 6 young adults (1–5 years) and 6 old adults (> 7 years) in the procedural rodent dPAL-task revealed significant age-related performance decline, evident in group differences in the percentage of correct decision during learning and the number of sessions needed to reach a predefined criterion. Response pattern analyses suggest decreased susceptibility to relative stimulus-position biases in young animals, facilitating PAL. Additional data from a subset of “overtrained” individuals (n = 7) and challenge sessions using a modified protocol (sPAL) further suggest that learning criteria routinely used in animal studies on PAL can underestimate the endpoint at which a stable performance is reached and that more conservative criteria are needed to improve construct validity of the task. To conclude, this is the first report of an age effect on dPAL and corroborates the role of mouse lemurs as valuable natural nonhuman primate models in aging research.

Intergroup bias is the tendency for people to inflate positive regard for their in-group and derogate the out-group. Across two online experiments (N = 922) this study revisits the methodological premises of research on language as a window into intergroup bias. Experiment 1 examined (i) whether the valence (positivity) of language production differs when communicating about an in- vs. out-group, and (ii) whether the extent of this bias is influenced by the positivity of input descriptors that were initially presented to participants as examples of how an in-group or out-group characterize themselves. Experiment 2 used the linear diffusion chain method to examine how biases are transmitted through cultural generations. Valence of verbal descriptions were quantified using ratings obtained from a large-scale psycholinguistic database. The findings from Experiment 1 indicated a bias towards employing positive language in describing the in-group (exhibiting in-group favoritism), particularly in cases where the input descriptors were negative. However, there was weak evidence for increased negativity aimed at the out-group (i.e., out-group derogation). The findings from Experiment 2 demonstrated that in-group positivity bias propagated across cultural generations at a higher rate than out-group derogation. The results shed light on the formation and cultural transmission of intergroup bias.

National character stereotypes, or beliefs about the personality characteristics of the members of a nation, present a paradox. Such stereotypes have been argued to not be grounded in the actual personality traits of members of nations, yet they are also prolific and reliable. Stereotypes of Canadians and Americans exemplify the paradox; people in both nations strongly believe that the personality profiles of typical Canadians and Americans diverge, yet aggregated self-reports of personality profiles of Canadians and Americans show no reliable differences. We present evidence that the linguistic behavior of nations mirrors national character stereotypes. Utilizing 40 million tweets from the microblogging platform Twitter, in Study 1A we quantify the words and emojis diagnostic of Canadians and Americans. In Study 1B we explore the positivity of national language use. In Studies 2A and 2B, we present the 120 most nationally diagnostic words and emojis of each nation to naive participants, and ask them to assess personality of a hypothetical person who uses either diagnostically Canadian or American words and emojis. Personality profiles derived from the diagnostic words of each nation bear close resemblance to national character stereotypes. We therefore propose that national character stereotypes may be partially grounded in the collective linguistic behaviour of nations.

Mouse lemurs are suggested to represent promising novel non-human primate models for aging research. However, standardized and cross-taxa cognitive testing methods are still lacking. Touchscreen-based testing procedures have proven high stimulus control and reliability in humans and rodents. The aim of this study was to adapt these procedures to mouse lemurs, thereby exploring the effect of age. We measured appetitive learning and cognitive flexibility of two age groups by applying pairwise visual discrimination (PD) and reversal learning (PDR) tasks. On average, mouse lemurs needed 24 days of training before starting with the PD task. Individual performances in PD and PDR tasks correlate significantly, suggesting that individual learning performance is unrelated to the respective task. Compared to the young, aged mouse lemurs showed impairments in both PD and PDR tasks. They needed significantly more trials to reach the task criteria. A much higher inter-individual variation in old than in young adults was revealed. Furthermore, in the PDR task, we found a significantly higher perseverance in aged compared to young adults, indicating an age-related deficit in cognitive flexibility. This study presents the first touchscreen-based data on the cognitive skills and age-related dysfunction in mouse lemurs and provides a unique basis to study mechanisms of inter-individual variation. It furthermore opens exciting perspectives for comparative approaches in aging, personality, and evolutionary research.

According to the relation-interpretation-competition-evaluation (RICE) hypothesis, compound word processing involves selecting a relational meaning (e.g., moonlight is ‘light from moon’) from a larger set of competing possible relational meanings. Prior lexical decision experiments with existing compound words have demonstrated that greater entropy of conceptual relations , i.e., greater competition between conceptual relations, impedes lexical processing speed. The present study addresses two unresolved issues: First, it is unclear whether the competition effect generalizes to the processing of novel compounds (e.g., grassladder ), and second, it is not yet known whether competition between possible relational meanings extends to compounds when they are read in a sentence context. A series of self-paced reading tasks examined whether the competition effect operates regardless of (i) compound type (existing vs. novel), and (ii) whether sentence context (semantically supportive vs. semantically non-supportive) moderates the competition effect. The experiments confirmed that reading times of novel and existing compounds read in sentences were impacted by entropy of conceptual relations. Moreover, the effect was equally strong in both sentence context types. Additional analyses indicated that relational meanings are more ambiguous and flexible across different contexts for novel compounds compared to existing compounds.

A central function of sensory systems is the gathering of information about dynamic interactions with the environment during self-motion. To determine whether modulation of a sensory cue was externally caused or a result of self-motion is fundamental to perceptual invariance and requires the continuous update of sensory processing about recent movements. This process is highly context-dependent and crucial for perceptual performances such as decision-making and sensory object formation. Yet despite its fundamental ecological role, voluntary self-motion is rarely incorporated in perceptual or neurophysiological investigations of sensory processing in animals. Here, we present the Sensory Island Task (SIT), a new freely moving search paradigm to study sensory processing and perception. In SIT, animals explore an open-field arena to find a sensory target relying solely on changes in the presented stimulus, which is controlled by closed-loop position tracking in real-time. Within a few sessions, animals are trained via positive reinforcement to search for a particular area in the arena (“target island”), which triggers the presentation of the target stimulus. The location of the target island is randomized across trials, making the modulated stimulus feature the only informative cue for task completion. Animals report detection of the target stimulus by remaining within the island for a defined time (“sit-time”). Multiple “non-target” islands can be incorporated to test psychometric discrimination and identification performance. We exemplify the suitability of SIT for rodents (Mongolian gerbil, Meriones unguiculatus) and small primates (mouse lemur, Microcebus murinus) and for studying various sensory perceptual performances (auditory frequency discrimination, sound source localization, visual orientation discrimination). Furthermore, we show that pairing SIT with chronic electrophysiological recordings allows revealing neuronal signatures of sensory processing under ecologically relevant conditions during goal-oriented behavior. In conclusion, SIT represents a flexible and easily implementable behavioral paradigm for mammals that combines self-motion and natural exploratory behavior to study sensory sensitivity and decision-making and their underlying neuronal processing.

Introduction The gray mouse lemur (Microcebus murinus) is an important nonhuman primate model in biomedical research. Numerous studies investigated mouse lemur behavior and possible factors underlying interindividual variation in both, animal personality and cognitive performance. Some effects, such as an age‐related decline in executive functioning, have robustly been found across laboratory colonies; however, little is known about the brain structural substrates in mouse lemurs. Methods Here, we provide first exploratory data linking in vivo magnetic resonance imaging of 34 mouse lemurs to performance in a standardized, touchscreen‐based task on object discrimination and reversal learning as well as to animal personality under different scenarios in an open field. Results High interindividual variability in both brain morphometric and behavioral measurements was found, but only few significant correlations between brain structure and behavior were revealed: Object discrimination learning was linked to the volume of the hippocampus and to temporal lobe thickness, while reversal learning was linked to thalamic volume and the thickness of the anterior cingulate lobe. Emergence latency into the open field correlated with volume of the amygdala. General exploration–avoidance in the empty open‐field arena correlated with thicknesses of the anterior cingulate lobe and fronto‐parietal substructures. Neophilia, assessed as exploration of a novel object placed in the arena, among others, related to the volume of the caudate nucleus. Conclusion In summary, our data suggest a prominent role of temporal structures (including the hippocampus) for learning capability, as well as thalamic and anterior cingulate structures for cognitive flexibility and response inhibition. The amygdala, the anterior cingulate lobe, and the caudate nucleus are particularly linked to animal personality in the open‐field setting. These findings are congruent with the comparative psychological literature and provide a valuable basis for future studies elucidating aspects of behavioral variation in this nonhuman primate model. In mouse lemurs, being valuable animal models in biomedical research, cognition and animal personality have been phenotyped through different behavioral paradigms. Data on underlying neurobiological substrates have been largely missing so far. We show behavioral performance to correlate with region‐specific anatomical measurements similar to the comparative psychological literature described in humans and other mammals, including nonhuman primates.

In the 1970s, Tavolga conducted a series of experiments in which he found behavioral evidence that the vocalizations of the catfish species Ariopsis felis may play a role in a coarse form of echolocation. Based on his findings, he postulated a similar function for the calls of closely related catfish species. Here, we describe the physical characteristics of the predominant call-type of Ariopsis seemanni. In two behavioral experiments, we further explore whether A. seemanni uses these calls for acoustic obstacle detection by testing the hypothesis that the call-emission rate of individual fish should increase when subjects are confronted with novel objects, as it is known from other vertebrate species that use pulse-type signals to actively probe the environment. Audio-video monitoring of the fish under different obstacle conditions did not reveal a systematic increase in the number of emitted calls in the presence of novel objects or in dependence on the proximity between individual fish and different objects. These negative findings in combination with our current understanding of directional hearing in fishes (which is a prerequisite for acoustic obstacle detection) make it highly unlikely that A. seemanni uses its calls for acoustic obstacle detection. We argue that the calls are more likely to play a role in intra- or interspecific communication (e.g. in school formation or predator deterrence) and present results from a preliminary Y-maze experiment that are indicative for a positive phonotaxis of A. seemanni towards the calls of conspecifics.

Executive function (EF) is a complex construct that reflects multiple higher-order cognitive processes such as planning, updating, inhibiting and set-shifting. Decline in these functions is a hallmark of cognitive ageing in humans, and age differences and changes in EF correlate with age-related differences and changes in association cortices, particularly the prefrontal areas. Here, we review evidence for age-related decline in EF and associated neurobiological changes in prosimians, New World and Old World monkeys, apes and humans. While EF declines with age in all primate species studied, the relationship of this decline with age-related alterations in the prefrontal cortex remains unclear, owing to the scarcity of neurobiological studies focusing on the ageing brain in most primate species. In addition, the influence of sex, vascular and metabolic risk, and hormonal status has rarely been considered. We outline several methodological limitations and challenges with the goal of producing a comprehensive integration of cognitive and neurobiological data across species and elucidating how ageing shapes neurocognitive trajectories in primates with different life histories, lifespans and brain architectures. Such comparative investigations are critical for fostering translational research and understanding healthy and pathological ageing in our own species. This article is part of the theme issue ‘Evolution of the primate ageing process’.

We aimed to test the effectiveness of checklists for emergency procedures on medical staff performance in intensive care crises. This is a prospective single-center randomized trial in a high-fidelity simulation center modeling an intensive care unit (ICU) in a tertiary care hospital in Germany. Teams consisted of 1 ICU resident and 2 ICU nurses (in total, n = 48). All completed 4 crisis scenarios, in which they were randomized to use checklists or to perform without any aid. In 2 of the scenarios, checklists could be used immediately (type 1 scenarios); and for the remaining, some further steps, for example, confirming diagnosis, were required first (type 2 scenarios). Outcome measurements were number of predefined items and time to completion of more than 50% and more than 75% of steps, respectively. When using checklists, participants initiated items faster and more completely according to appropriate treatment guidelines (9 vs 7 items with and without checklists, P < .05). Benefit of checklists was better in type 2 scenarios than in type 1 scenarios (2 vs 1 additional item, P < .05). In type 2 scenarios, time to complete 50% and 75% of items was faster with the use of checklists (P < .005). Use of checklists in ICU crises has a benefit on the completion of critical treatment steps. Within the type 2 scenarios, items were fulfilled faster with checklists. The implementation of checklists for intensive care crises is a promising approach that may improve patients' care.