Table 1. This is an overview of the eye tracking and fNIRS findings when altruistic behavior is measured as a continuous variable (frequency of helping, ranging from 0 to 6).

Note that a positive ß value reflects that this variable is positively associated with altruistic behavior. Underlying data are available through the Open Science Framework, https://osf.io/znjr7/.

Predictor variables at 7 months	Altruistic behavior as a continuous measure at 14 months
Eye tracking
first look fearful faces	ß = 0.362, p = 0.004
looking bias fearful faces	ß = −0.404, p = 0.001
looking bias fearful eyes	ß = −0.319, p = 0.01
fNIRS
left dlPFC fearful faces	ß = −0.272, p = 0.037*
right dlPFC fearful minus angry faces	ß = −0.335, p = 0.008

*Note that this reflects the value when controlling for maternal engagement and that left dlPFC to fearful faces also predicted looking bias to fearful faces.

Abbreviations: dlPFC, dorsolateral prefrontal cortex; fNIRS, functional near-infrared spectroscopy.