A new study has suggested that testicle size plays a role in whether or not a guy is an involved dad, but this is one time less is more: the smaller the family jewels, the better the family man. Prior research has already suggested that dudes with higher testosterone levels are less into raising kids, but this study, published in the Proceedings of the National Academy of Sciences, is the first to find an independent correlation between testicle volume and parenting. Researchers questioned whether testicle volume, more closely linked to sperm count and quality rather than testosterone levels, played a part.

The higher the testosterone levels and larger the testicles, the smaller the amount of direct paternal caregiving by dads as reported by parents in the study.

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