Table 3. Relationship between contributions and HRV in the PGG without punishment.

	PGG1	PGG2	PGG3
Decision-	1.20*	1.16**	0.79†
	(0.60)	(0.40)	(0.43)
Individual Effects	Yes	Yes	Yes
N	224	208	224

Note: Results of fixed-effects regressions of HRV during the contribution decision on the level of contributions. The average HRV across all participants for the corresponding decisions was 1.79. Specifications PGG1-3 use alternative measures of HRV . PGG1 uses the direct measure at the moment of decision making, PGG2 and PGG3 normalize this value by the average individual during the experiment and the round, respectively. Standard errors (clustered by individuals) are in brackets. **p < 0.01, * p < 0.05, ^†p < 0.1.