Social interactions during early life can have large impacts on the development of behavioral patterns, cognitive abilities and the brain. Research in humans has found correlations between early experiences and cognitive-behavioral traits. This project will test these relationships using manipulative experiments with swordtail fish. Previous research in fish has determined that a particular kind of stressful social interaction known as sexual conflict (where males and females disagree over mating rates) can lead to an increase in female brain size. Meanwhile, other research has suggested that having to navigate different kinds of social interactions (also known as social complexity) may result in enhanced cognitive capabilities. The research will test these two competing hypotheses by controlling social conditions during rearing in a fish system that exhibits social complexity and sexual conflict. There are three different types of swordtail males, which represent different levels of sexual conflict towards females (high, low or intermediate sexual conflict). By raising female swordtails in social environments that vary in the type of males present, researchers can quantify how sexual conflict and social complexity shape adult behaviors (including anxiety, aggression and sociability), cognition (learning abilities), and determine which brain regions grow or diminish in response to different social experiences. This research will have broader impacts that affect both local and national students through the investigator's efforts to incorporate her research into local high school outreach program and the Freshman Research Initiative course at the University of Texas, and through student-initiated national media products (YouTube) on this research.
Sexual conflict, the mismatch in optimal mating rates between the sexes, is ubiquitous across animals. While the morphological consequences of this struggle are well-studied, less is known about the behavioral and cognitive consequences of sexual conflict. In this study, the investigator will experimentally examine the developmental effects of sexual conflict in the swordtail fish (Xiphophorus nigrensis), which has three alternative male phenotypes that represent different levels of sexual conflict towards females: courting males (low conflict), coercive males (high conflict), and males who both court and coerce (mixed conflict). Female swordtails will be raised from birth to early adulthood in one of five social environments that vary in levels of both sexual conflict and social complexity. At adulthood, females will partake in a broad range of assays to determine how social experiences shape behavioral and cognitive traits. These assays evaluate anxiety, sociability and exploratory tendencies as well as associative learning, cognitive flexibility and social cognition capabilities. Female brains will be examined to determine how social environment influences the development of distinct brain regions and receptor distribution of candidate social pathways including isotocin and synaptic plasticity markers. The results of this experiment will identify how the social environment influences the development of behavioral tendencies, as well as directly test competing hypotheses for enhanced cognition and brain development (sexual conflict versus social complexity). It will also identify which brain regions (focusing on the social decision-making network) undergo differential development in response to specific social interactions associated with conflict and complexity.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
