To Peck or Not To Peck: The influence of early-life social environment on response inhibition and impulsive aggression in Japanese quails
Alizée VernouilletiD, Kathryn WillcoxiD, Reinoud AllaertiD, Anneleen DewulfiD, Wen ZhangiD, Camille Aurélie TroisiiD, Sophia KnochiD, An MarteliD, Luc LensiD, Frederick VerbruggeniD
Abstract
Deficits in response inhibition (i.e., the ability to suppress inappropriate responses) may contribute to increased impulsive aggression (i.e., unplanned behaviors that harm others). Since early-life environment might influence the development of response inhibition, it could also indirectly affect impulsive aggression. However, this relationship has rarely been directly examined. Here, we investigated whether response inhibition is associated with impulsive aggression and whether this relationship explains the effects of early-life social environments on impulsive aggression in juvenile Japanese quails (Coturnix japonica). Quails (n = 120) were raised in two social conditions: Small groups of five birds or Large groups of 15 birds. Response inhibition was assessed using the Barrier and Cylinder tasks, while impulsive aggression was measured in two contexts - within a group of five familiar individuals and in a dyad with an unfamiliar individual. We found that some aspects of response inhibition were related to impulsive aggression. Furthermore, quails reared in small groups showed significantly poorer response inhibition than those reared in large groups. Yet, impulsive aggression did not significantly differ between the two conditions. These findings suggest that, while impulsive aggression is partly related to response inhibition, other factors mitigate the effects of early social environments on its expression.
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In-depth summary
Claude Opus 5.5 · xhigh effort · 8 Nov 2026 · from the full text of version 2 (29 Apr 2025) · CC BY 4.0
Japanese quails reared in groups of 15 versus five pecked a transparent cylinder less, but rearing group size did not change impulsive aggression in either context.
Most evidence that response inhibition deficits drive impulsive aggression is correlational, so it has rarely been tested directly whether early-life conditions shape both traits or whether one causes the other. By manipulating rearing group size in Japanese quails while holding other conditions constant, the study tests whether the social environment shapes inhibition and aggression and whether the two vary together within individuals.
Key results
ShownBirds reared in large groups spent less time pecking at the transparent cylinder. Group size did not affect detour success in either task, and it did not affect pecking at the transparent barrier.
Cylinder pecking time (birds that pecked, n = 82): Large 11.64 ± 1.92 s vs Small 18.70 ± 2.50 s; χ^2 = 6.256, df = 1, p = 0.012. Barrier pecking (n = 100) did not differ by group (χ^2 = 1.608, d.f. = 1, p = 0.205). Success in neither task was explained by group size, sex or body weight. · Influence of group size on response inhibition; Figure legends
ShownRearing group size did not change aggression toward familiar groupmates or toward an unfamiliar partner. Sex and body weight did predict aggression scores.
Unfamiliar Individual score (PC1): group χ^2 = 0.001, p = 0.973. Familiar Group score (PC2): group χ^2 = 0.183, p = 0.670 (n = 120). Males were more aggressive in both (PC1 χ^2 = 4.318, p = 0.038; PC2 χ^2 = 8.554, p = 0.004). Heavier birds were more aggressive toward familiar birds (χ^2 = 6.002, p = 0.016). · Influence of group size on impulsive aggression; Figure legends
SuggestedInhibition and aggression were only partly linked, and in inconsistent directions. Longer cylinder pecking tracked more aggression toward an unfamiliar bird, yet birds that detoured the barrier successfully were more aggressive toward familiar birds, the opposite of the prediction.
Cylinder pecking time vs PC1: r = 0.221, t = 2.199, d.f. = 94, p = 0.030. Barrier success vs PC2: t = 2.757, d.f. = 20.79, p = 0.012. Barrier measures vs PC1 were null (pecking r = -0.018, p = 0.844). Cylinder success vs PC1 was marginal (t = 2.072, p = 0.053). · Relationship between response inhibition and…; Relationship between response inhibition and…
ShownNeither the two detour tasks nor the two aggression contexts agreed with each other. Each pair appears to capture separate, context-dependent facets rather than a single trait.
Among 95 birds that interacted in both tasks, the tetrachoric correlation for success was -0.250 and pecking time gave r = -0.116 (t = -1.129, df = 93, p = 0.262); only one bird succeeded in both. Aggression PCA (n = 120): five components with eigenvalue above 1 explained 78.1 % of variance, and each task loaded on separate components. · Statistical analyses; Repeatability of response inhibition; Repeatability of impulsive aggression
ShownMost birds touched or pecked the transparent apparatus rather than detouring cleanly. Fewer birds detoured successfully in the Cylinder task, which, unlike the Barrier task, included no training with an opaque version.
Barrier: 19 successful detours, 93 detoured after touching, seven touched without detouring, one did not interact. Cylinder first trial: 14 successful, 46 unsuccessful detours, 36 touched without detouring, 24 did not interact. Mean pecking time was 17.5 (SE 1.4) s at the barrier (n = 100) and 15.0 (SE 1.6) s at the cylinder (n = 82). · Overview of Barrier task; Overview of Cylinder task; Relationship between response inhibition and…
Methods, data and reproducibility
120 quails were randomly assigned on day 2 post-hatch to groups of five or 15. They were tested on Barrier and Cylinder detour tasks at 24-33 days, then on aggression with familiar groupmates and with an unfamiliar partner at 39-41 days. Analyses used correlations, PCA of aggression measures, and GLMs with group size, sex and body weight.
- Juvenile Japanese quails hatched together, then randomly assigned to Small (five birds) or Large (15 birds) rearing groups across four lofts · Japanese quail (Coturnix japonica) · n = 120 (60 females, 60 males; 60 per condition)
- Response inhibition analysis subsets: birds that interacted with or pecked the Barrier and Cylinder apparatus · Japanese quail (Coturnix japonica) · n = Barrier 119 (100 pecked); Cylinder 96 (82 pecked)
- Video recordings of all experimental trials · Japanese quail (Coturnix japonica) · Zenodo record 13361318
- R code and behavioral data extracted from BORIS · Japanese quail (Coturnix japonica) · OSF 2b5uy
- Methods & tools
- BORIS v.7.13 (video coding, Cohen's kappa), R 4.3.2, glmmTMB, DHARMa, psych, FactoMineR, factoextra, Rmisc, ggplot2, Barrier (transparent detour) task, Cylinder task, Confirmatory factor analysis / structural equation modelling (abandoned for poor fit)
- Code & protocols
- https://osf.io/2b5uy/
- Data & accessions
- https://zenodo.org/records/13361318https://osf.io/2b5uy/
- Software & environment
- R version 4.3.2 (glmmTMB, DHARMa, psych, FactoMineR, factoextra, Rmisc, ggplot2, ggsignif, ggpubr, patchwork, wesanderson); video coding in BORIS v.7.13
- Reproducibility gaps
- R package versions are not specified. The GLM statistics for response inhibition (Table 2) and the CFA/SEM details sit in tables or supplementary material that are not in the text.
Limitations (6)
- Group size was confounded with density, because Small and Large groups lived in enclosures of the same size. The authors suggest this may explain the missing group effect on aggression and call for separating the two factors. · stated by the authors
- Confirmatory factor analysis found weak correlations among indicators, and no SEM fit adequately. The analyses therefore fell back on correlations and t-tests, which cannot show the direction of the inhibition-aggression link. · stated by the authors
- The Barrier and Cylinder tasks may tap different processes, or simply a tendency to peck. Only the Barrier task included training with an opaque barrier, so differences in learning could explain why performance did not carry over between tasks. · stated by the authors
- Birds were tested as juveniles near the onset of sexual maturity. Inhibition and aggression may not have been fully developed, and differences in maturation timing could add variation between individuals. · stated by the authors
- Birds sharing an enclosure are not independent, yet the GLMs as described include only group condition, sex and body weight, with no enclosure or loft term. With only one Large enclosure per loft, the group-size effects may be pseudoreplicated. · noted in this summary
- Many tests were run at alpha 0.05 with no stated correction for multiple comparisons, using first-trial data only. The modest associations (e.g., p = 0.030, p = 0.012) therefore need replication. · noted in this summary
Who should read:Read this if you study how early social rearing shapes inhibitory control or aggression in birds, or use detour tasks (barrier or cylinder) to measure response inhibition.
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