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Biology subjects

Fischer, D.

Publications and source records attributed to Fischer, D..

2 recordsLinked to original sources

How cognitive and environmental constraints influencethe reliability of simulated animats in groups

Evolving in groups can either enhance or reduce an individuals task performance. Still, we know little about the factors underlying group performance, which may be reduced to three major dimensions: (a) the individuals ability to perform a task, (b) the dependency on environmental conditions, and (c) the perception of, and the reaction to, other group members. In our research, we investigated how these dimensions interrelate in simulated evolution experiments using adaptive agents equipped with Markov brains (\"animats\"). We evolved the animats to perform a spatial-navigation task under various evolutionary setups. The last generation of each evolution simulation was tested across modified conditions to evaluate and compare the animats reliability when faced with change. Moreover, the complexity of the evolved Markov brains was assessed based on measures of information integration. We found that, under the right conditions, specialized animats were as reliable as animats already evolved for the modified tasks, that interaction between animats was dependent on the environment and on the design of the animats, and that the task difficulty influenced the correlation between the performance of the animat and its brain complexity. Generally, our results suggest that the interrelation between the aforementioned dimensions is complex and their contribution to the groups task performance, reliability, and brain complexity varies, which points to further dependencies. Still, our study reveals that balancing the group size and individual cognitive abilities prevents over-specialization and can help to evolve better reliability under unknown environmental situations.\n\nAuthor SummaryThe ability to adapt to environmental changes is an essential attribute of organisms which have had evolutionary success. We designed a simulated evolution experiment to better understand the relevant features of such organisms and the conditions under which they evolve: First, we created diverse groups of cognitive systems by evolving simulated organisms (\"animats\") acting in groups on a spatial-navigation task. Second, we post-evolutionary tested the final evolved animats in new environments-not encountered before- in order to test their reliability when faced with change. Our results imply that the ability to generalize to environments with changing task demands can have complex dependencies on the cognitive design and sensor configuration of the organism itself, as well as its social or environmental conditions.

animal behavior and cognition

Maternal glucocorticoids do not predict reproductive investment nor breeding success in a free-ranging bird.

The hormone corticosterone (CORT)) has been hypothesized to be linked with fitness, but the directionality of the relationship is unclear. The "CORT-fitness hypothesis" proposes that high levels of CORT arise from challenging environmental conditions, resulting in lower reproductive success (a negative relationship). In contrast, the "CORT-adaptation hypothesis" suggests that, during energetically demanding periods, CORT will mediate physiological or behavioural changes that result in increased reproductive investment and success (a positive relationship). During two breeding seasons, we experimentally manipulated circulating CORT levels in female tree swallows (Tachycineta bicolor) prior to egg laying, and measured subsequent reproductive effort, breeding success, and maternal survival. When females were recaptured during egg incubation and again during the nestling stage, the CORT levels were similar among individuals in each treatment group, and maternal treatment had no effect on indices of fitness. By considering variation among females, we found support for the "CORT-adaptation hypothesis"; there was a significant positive relationship between CORT levels during incubation and hatching and fledging success. During the nestling stage CORT levels were unrelated to any measure of investment or success. Within the environmental context of our study, relationships between maternal glucocorticoid levels and indices fitness vary across reproductive stages. SUMMARY STATEMENTMaternal corticosterone levels predict breeding success of female tree swallows.

zoology