Why Partisans Treat Opponents Like Outsiders: Experimental Evidence

🧪 What Was Tested

This study probes how political identification and ideology shape everyday social behavior. Behavioral games—dictator, trust, and public goods—were used to measure altruism, trust, and willingness to contribute to mutual benefits while varying the perceived party identity of interaction partners.

• Dictator game: measured unilateral generosity toward same- or opposite-party partners
• Trust game: measured trusting behavior and trustworthiness across party lines
• Public goods game: measured contributions to a shared benefit when paired with co- or cross-party partners

🔎 Key Findings

Partisan identifiers (those who say they identify with the Democratic or Republican Party) and ideological extremists (self-identified liberals or conservatives) show substantially stronger affective biases than politically unaffiliated individuals and ideological moderates.

• Partisan subjects are less altruistic toward opposing-party partners.
• Partisan subjects display lower trust in opponents and are less likely to reciprocate trust.
• Partisan subjects contribute less to mutually beneficial public goods when paired with members of the opposing party.

📈 How This Fits With Other Work

Compared to prior behavioral studies, the results suggest rising levels of affective polarization in everyday social interactions—approaching the entrenched intergroup divisions more commonly associated with conflict or post-conflict societies.

💡 What This Implies and Possible Remedies

Findings indicate that partisan identity and ideology shape basic social preferences, not just political opinions. To reduce affective polarization, inter-group contact emerges as a promising mechanism for increasing interpersonal trust and bridging political divides.

⚖️ Why It Matters

These behavioral shifts in generosity, trust, and cooperative contribution have implications for social cohesion, cross-party collaboration, and the functioning of democratic institutions in the Trump era and beyond.