Table 1. Payoff matrix of one-round IADC.

Role	Participant	Initial endowment (MU)	Individual contribution (Ii)	Group pool (G)	Payment
					Attackers lose GAttacker   ≤ GDefender	Attackers win GAttacker > GDefender
					Leftover	Leftover	Spoil
Attack	Attacker-1	20	IAttacker-1	GAttacker	20 − IAttacker-1	20 − IAttacker-1	(60 − GDefender)/3
	Attacker-2	20	IAttacker-2		20 − IAttacker-2	20 − IAttacker-2	(60 − GDefender)/3
	Attacker-3	20	IAttacker-3		20 − IAttacker-3	20 − IAttacker-3	(60 − GDefender)/3
Defend	Defender-1	20	IDefender-1	GDefender	20 − IDefender-1	0	0
	Defender-2	20	IDefender-2		20 − IDefender-2	0	0
	Defender-3	20	IDefender-3		20 − IDefender-3	0	0

Table note: For each round, each individual received an initial endowment of 20 MUs (Monetary Units).

Each individual decided the amount (I_i , 0 ≤ I_i ≤ 20) to the group’s pool G (0 ≤ G ≤ 60, G_Attacker = I_Attacker-1+I_Attacker-2+I_Attacker-3, G_Defender = I_Defender-1+I_Defender-2+I_Defender-3). When G_Attacker ≤G_Defender, attackers failed and defenders survived and all six individuals kept their remaining endowment (leftovers, 20 – I_i). When G_Attacker >G_Defender, defenders failed and left with 0. The attackers won and took away defenders’ remaining MU (spoils from winning, 60 – G_Defender), which were divided equally among attacker group members (each attacker: (60 – G_Defender)/3) and added to their remaining endowments (20 – I_Attacker-i).