DOI: 10.5061/dryad.pk0p2nh2d
title: Social fish have larger brains and greater relative telencephalon sizes: support for the social brain hypothesis from wild, intraspecific comparisons

description: The Social Brain Hypothesis posits that complex social environments drive
 the evolution of larger brains and the enlargement of specific brain
 regions. Among species comparisons often report contrasting relationships
 between social complexity and brain size, potentially due to confounding
 effects of phylogeny, morphology, and ecology. Here, we explore this
 relationship in a single fish species, combining behavioural observations
 and brain measurements of two wild populations of the cichlid
 Neolamprologus brevis, which occupy similar ecological niches across its
 range but inhabit contrasting social environments depending on local
 shelter abundance. This dataset contains behavioural and neuroanatomical
 measurements from two wild populations of the shell-dwelling cichlid
 Neolamprologus brevis used to test the social brain hypothesis. The data
 include total brain volume, volumes of five brain regions (telencephalon,
 optic tectum, cerebellum, medulla, and hypothalamus), body weight, sex,
 and population identity for 43 individuals. Neighbour density and
 behaviour frequency summaries are included. The dataset also contains R
 code used for all statistical analyses and figure generation. Data can be
 reused for comparative neuroanatomy, behavioural ecology, and allometric
 scaling analyses. No ethical or legal restrictions apply.
description: # Social fish have larger brains and greater relative telencephalon sizes:
 support for the social brain hypothesis from wild, intraspecific
 comparisons Dataset DOI:
 [10.5061/dryad.pk0p2nh2d](10.5061/dryad.pk0p2nh2d) ## Description of the
 data and file structure This dataset was collected to examine the
 relationship between social environment and brain morphology in the
 shell-dwelling cichlid *Neolamprologus brevis*. It includes measurements
 of total brain volume and five major brain regions, as well as
 individual-level data on body weight, sex, population, and local neighbour
 density. The dataset supports a study testing the Social Brain Hypothesis
 using intraspecific comparisons in a wild fish system. ### Files and
 variables #### File: brevisBehaviourData.csv **Description:** Data of
 behavioural observations for each focal fish, including frequency of
 behaviours and neighbour density. ##### Variables * observationID: Unique
 identifier for each individual fish * behavioralCategory: Categorized
 behaviour type (e.g., social interaction, aggression, etc.) *
 population: Population identity (`chezi` = –social, `chekonde` = +social)
 * count: Number of observed behaviours in the given category *
 total_time: Total time of the observation window (seconds) *
 intermediateNeighbour: Number of conspecifics within a 50 cm radius around
 the focal fish #### File: brevisBrainData.csv **Description:**  #####
 Variables * id: Unique identifier for each individual fish *
 population: Population identity (`chezi` = –social, `chekonde` = +social)
 * bodyW: Body weight (g) * standL: Standard body length (cm) * sex: Sex of
 the individual (`male`, `female`) * telV: Telencephalon volume (mm3) *
 optV: Optic tectum volume (mm3) * cerV: Cerebellum volume (mm3) *
 medV: Medulla volume (mm3) * hypV: Hypothalamus volume (mm3) *
 totalV: Total brain volume (mm3) #### File: analysis_script.R
 **Description:** R script used for all statistical analysis and figure
 generation in the associated manuscript. Includes linear models,
 regression plots, and summary statistics for brain volume, brain regions,
 and behavioural comparisons. Missing values are indicated by `NA`. ##
 Code/software The dataset can be viewed and analyzed using **R** (version
 4.3.0 or later), which is free and open-source statistical software
 available at [https://www.r-project.org/](https://www.r-project.org/). The
 analysis script (`analysis_script.R`) includes the full workflow used to
 generate the results and figures presented in the associated publication.
 The script performs the following: * Loads raw behavioural and brain
 morphology datasets * Runs linear models for total brain volume and brain
 region volumes * Performs Wilcoxon tests and model-based comparisons for
 neighbour density * Generates all plots (Figures 2–4 and supplementary
 figures) using `ggplot2` The following R packages were used in the
 analysis: * `ggplot2` (v3.4.0) – for data visualization * `lme4` (v1.1-33)
 – for linear models * `emmeans` (v1.8.5) – for estimated marginal means *
 `performance` (v0.10.2) – for model diagnostics * `ggpubr` (v0.6.0) – for
 figure arrangement * `gtsummary` (v1.7.1) – for reporting tables *
 `ggpredict` from `ggeffects` (v1.2.1) – for marginal effects plotting The
 script assumes the data files (`brevisBrainData.csv`,
 `brevisBehaviourData.csv`) are located in the same working directory as
 the R script. ## Access information Other publicly accessible locations of
 the data: * This dataset is not hosted elsewhere. It is only available via
 Dryad. Data was derived from the following sources: * All data were
 collected by the authors as part of the study. No external datasets were
 used.