Biological Bases of Individual Variation in Paternal Nurturance

40 biological fathers of children age 2 months or younger who are currently cohabitating with the child's mother will be scanned on two separate occasions. The optional second visit will occur after 2 months have passed since the first scan. In the first visit, fathers will receive two MRI scans, one before and one after completing one of the two interventions. Prior to the MRI scan, a blood sample will be collected for measurement of hormone levels. Fathers will be positioned in the MRI scanner where they will receive structural and functional MRI scans of their brain while they listen to auditory stimuli: unknown cries, own cries, and tone controls. Blood sample collection and intervention will not be conducted during the second visit.