# The expression of father-daughter bond behaviors influences adult partner attachment in titi monkeys

## TL;DR

This study explores how father-daughter bonds in monkeys influence adult attachment behaviors and brain activity, revealing parallels to human relationships.

## Contribution

A novel method for quantifying bond-related behaviors and linking early attachment patterns to adult neural and behavioral outcomes in socially monogamous monkeys.

## Key findings

- Females with higher juvenile parent preference maintained closer father proximity six months post-pairing.
- Higher juvenile proximity after separation predicted increased partner proximity in adulthood.
- Neural activity in social bonding regions decreased with higher juvenile proximity, suggesting stress buffering benefits.

## Abstract

Coppery titi monkeys (Plecturocebus cupreus) are socially monogamous monkeys that display strong pair bonds similar to human romantic attachments, preceded by infant attachment to their fathers. To understand how father-daughter bonds impact adult relationship dynamics, we established a novel method for quantifying expression of bond-related behaviors. We assessed behavioral and neural correlates of preference, stress buffering, and separation distress to identify how females’ current and former attachment figures impact female attachment. Whereas all females (n = 9) shifted to preferring their partner over father six-months post-pairing, females that exhibited higher expression of juvenile parent preference maintained a relationship with their father six-months post-pairing, as evidenced by higher-than-expected father proximity. Higher expression of juvenile measures of proximity following a brief separation predicted slightly increased partner proximity in adulthood. Neural activity patterns in brain regions assessed pre- and post-pairing showed high similarity in glucose metabolism, despite overall activity being lower post-pairing. While there was some inconsistency in results, higher expression of juvenile proximity following a separation was associated with enhanced reduction in activity within social bonding brain regions (social salience network, periaqueductal gray, cerebellum), suggesting a potential stress buffering benefit via reduced threat-related brain activation, like that seen in high-quality human relationships. These findings advance current knowledge of how early relationships may shape adult bond-related behavior and neural activity.

The online version contains supplementary material available at 10.1038/s41598-025-31143-6.