Coevolution of relative brain size and life expectancy in parrots

2022

Ecology and Evolution

Self Cite

There is a long‐standing interest in the effect of relative brain size on other life history variables in a comparative context. Historically, residuals have been used to calculate these effects, but more recently it has been recognized that regression on residuals is not good practice. Instead, absolute brain size and body size are included in a multiple regression, with the idea that this controls for allometry. I use a simple simulation to illustrate how a case in which brain size is a response variable differs from a case in which relative brain size is a predictor variable. I use the simulated data to test which modeling approach can estimate the underlying causal effects for each case. The results show that a multiple regression model with both body size and another variable as predictor variable and brain size as response variable work well. However, if relative brain size is a predictor variable, a multiple regression fails to correctly estimate the effect of body size. I propose the use of structural equation models to simultaneously estimate relative brain size and its effect on the third variable and discuss other potential methods.

Section: Smeelementioning

confidence: 99%

Using relative brain size as predictor variable: Serious pitfalls and solutions

2022

Ecology and Evolution

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“…Structural equation models allow for the inclusion of measurement error, imputation of missing data and phylogenetic coveriance (Smeele et al 2022). Furthermore, the Bayesian implementation is useful in cases with low sample size.…”

Section: Discussionmentioning

confidence: 99%

“…It contains regressions for each variable and allows brain size to be response and outcome variable simultaneously (Bowen and Guo 2011). Structural equation models have been used before to include relative brain size in a comparative study in combination with phylogeny, measurement error and imputation (Smeele et al 2021). The aim of this current paper is to show the estimation error in ordinary linear regressions using a simulation and propose a simple Bayesian structural equation model as a solution that can be easily adapted to most comparative studies.…”

Section: Introductionmentioning

confidence: 99%

Using relative brain size as predictor variable: serious pitfalls and solutions

2022

Preprint

Self Cite

There is a long standing interest in the effect of relative brain size on other life history variables in a comparative context. Historically, residuals have been used to calculate these effects, but more recently it has been recognised that regression on residuals is not good practice. Instead, absolute brain size and body size are included in a single regression, with the idea that this controls for allometry. This practice leads to a second, potentially even greater estimation error when both relative brain size and body size are a cause of the third variable in question. In this study I use a simple simulation to show how the effect of body mass is masked if absolute brain size is included. I propose the use of structural equation models to simultaneously estimate relative brain size and its effect on the third variable, leaving the effect of body mass unconfounded.

“…This is an interesting nding considering the evolutionary distance between mammals and birds. Birds also have differently structured brains compared to mammals although their forebrain (nido-and mesopallium) represents a homologous structure to the mammalian neocortex 28, [42][43][44] . Like the neocortex, this telencephalic structure ful lls higher cognitive functions even if it lacks the cortex-typical lamination and is structured differently 45 .…”

Section: Discussionmentioning

confidence: 99%

What did I do? Memory for own actions in parrots

Ortiz

Champenois

et al. 2022

Preprint

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The ability to recall one’s past actions is a crucial prerequisite for mental self-representation and episodic memory. We studied whether blue-throated macaws, a social macaw species, can remember their previous actions. The parrots were trained to repeat four previously learned actions upon command. Test sessions included repeat trials, double repeat trials and trials without repeat intermixed to test if the parrots repeated correctly, only when requested and not relying on a representation of the last behavioral command. Following their success, the parrots also received sessions with increasing time delays preceding the repeat command and successfully mastered 12–15 sec delays. The parrots successfully transferred the repeat command spontaneously at first trial to three newly trained behaviors they had never repeated before, and also succeeded in a second trial intermixed with already trained actions (untrained repeat tests). This corroborates that successful repeating is not just an artifact of intense training but that blue-throated macaws can transfer the abstract “repeat rule” to untrained action. This implies that an important aspect of self-representation has evolved in this avian group and might be adaptive, which is consistent with the complex socio-ecological environment of parrots and previous demonstrations of their complex cognition.