In Search of Prosocial Behaviors in Rodents: Paradigms, Behavioral Analyses, and Mediating Factors

Abstract

From sharing resources to caring for offspring, prosociality allows animals to survive. In humans, mental health challenges affecting sociability are often associated with reduced quality of life. Despite years of research aimed at understanding the behavioral and neural mechanisms of prosociality in humans, non-human primates, and other social mammals (including rodents), little is known about the specific processes involved. Consequently, it is crucial to standardize the assessment of prosocial behaviors in rodents to promote the development of valid experimental paradigms and methodologies. Such research will enhance understanding of prosociality and its implications for mental and physical health challenges.

The first study of this thesis used a quasi-experimental design to examine two strains of adolescent rats, Long-Evans (n = 8) and Sprague-Dawley (n = 12), in a modified double operant box paradigm that allowed paired rats to share food rewards. Both strains were randomly assigned to either a pretrained or a naive group. To assess vicarious learning, dyads exchanged roles during the second phase of the experiment. Performance for all groups (Long-Evans versus Sprague-Dawley; Original Actors versus Vicarious Observers; Pretraining versus No Pretraining) and transitional probabilities of behavioral sequences were analyzed. The findings indicated that pretraining mediated behavioral responses, whereas vicarious learning had minimal influence on task performance. This initial groundwork highlighted the pivotal role of variables such as pretraining, behavioral analysis, and task contingency in mediating prosocial behaviors.

Building on these observations, Study Two characterized current findings on prosocial paradigms in rodents through a scoping review. A research librarian devised an extensive search strategy encompassing five databases - APA PsycInfo, Embase, MEDLINE, Scopus, and Web of Science - covering the period from January 2000 to 2021. Subsequently, a semi-supervised machine learning technique utilizing ASReview was employed to update the search and gather studies published from 2021 to 2023. In total, 80 articles were included. The results were as follows: (1) Three categories of tasks were identified (i.e., cooperation, helping, and sharing tasks). Rodents demonstrated the ability to perform prosocial actions in all three categories; (2) notable discrepancies were observed in reported methodologies, such as the omission of animal characteristics, housing conditions, and experimental protocols, (3) behavioral analyses were identified as crucial for studying prosociality in rodents, yet many studies overlooked their inclusion. Finally, (4) important mediating factors were identified as critical determinants in the assessment of prosociality in rodents, including sex, age, strain, housing, familiarity, food restriction, aggression, and dominance. These findings collectively provide insights for future studies into the influence of mediating factors and highlight the significance of behavioral analyses in the expression of prosocial behaviors in rodents.

Considering the observations from Study Two, Study Three presented a conceptual framework that (1) reframed prosociality as a set of complex behaviors emerging in response to environmental determinants that cannot be reduced to a single set of data, (2) highlighted important methodological considerations, mediating variables, and behavioral analyses that influence prosocial behaviors, and (3) introduced a decision tree as a dynamic element within this framework to guide researchers. The conceptual framework and decision tree provide a robust foundation for the continued use of existing models and the development of new paradigms. Integrating this conceptual framework into research practices will contribute to the advancement of knowledge in the field of rodent prosociality and foster greater confidence in the validity and reproducibility of study findings.

Taken together, these three studies make a substantial contribution to the literature by highlighting crucial factors involved in rodent prosociality, including mediating variables and behavioral analyses. Moreover, the development of a conceptual framework marks a pivotal advancement in the field, leading to a deeper understanding of rodent prosociality and its underlying behavioral mechanisms. This foundational work paves the way for future research on prosociality impairments observed in mental health disorders, neurodevelopmental conditions, and neurological impairments.