Emotional Contagion in Code: How GitHub Emoji Reactions Shape Developer Collaboration

TL;DR

This study investigates how emoji reactions on GitHub influence developer interactions, revealing strong positive emotional contagion that significantly impacts discussion dynamics and collaboration outcomes.

Contribution

It provides empirical evidence that emoji reactions actively shape emotional and collaborative patterns in software development discussions.

Findings

Positive sentiment dominates discussions (57.4%)

Positive emotional cascades outnumber negative ones 23:1

Strong emotional contagion with r=0.679 and d=2.393

Abstract

Developer communities increasingly rely on emoji reactions to communicate, but we know little about how these emotional signals spread and influence technical discussions. We analyzed 2,098 GitHub issues and pull requests across 50 popular repositories, examining patterns in 106,743 emoji reactions to understand emotional contagion in software development. Our findings reveal a surprisingly positive emotional landscape: 57.4% of discussions carry positive sentiment, with positive emotional cascades outnumbering negative ones 23:1. We identified five distinct patterns, with "instant enthusiasm" affecting 45.6% of items--nearly half receive immediate positive reinforcement. Statistical analysis confirms strong emotional contagion (r=0.679, p<0.001) with a massive effect size (d=2.393), suggesting that initial reactions powerfully shape discussion trajectories. These findings challenge assumptions about technical discourse being purely rational, demonstrating that even minimal emotional signals create measurable ripple effects. Our work provides empirical evidence that emoji reactions are not mere decoration but active forces shaping collaborative outcomes in software development.