Only certain canines have the discipline to become guide dogs for the blind, and the best ones had mothers that showed them "tough love" when they were puppies, researchers said Monday.
When dog moms allowed their puppies to learn on their own in their first five weeks of life, without coddling them too much, their puppies grew up to be better guide dogs, said the report in the Proceedings of the National Academy of Sciences.
Puppies with mothers who doted on them grew up to be anxious and more afraid of new situations, and tended to fail out of a rigorous training program to assist the blind.
The study was done at a facility in New Jersey called The Seeing Eye, which breeds and trains seeing eye dogs.
Researchers at the University of Pennsylvania essentially embedded themselves at The Seeing Eye, taking video and closely observing 23 mothers and their 98 puppies for their first five weeks of life, said the report.
"We wanted to know if we could differentiate the moms based on how they interacted with their puppies," said lead author Emily Bray.
"We documented things like her nursing position, how much time she spent looking away from the puppies and how much time she spent in close proximity to her puppies or licking and grooming them."
Two years later, researchers went back to catch up with the dogs and found that those with more attentive mothers were less likely to graduate and become guide dogs.
A key measure of success was whether puppies' mothers nursed them while standing, or lying down.
"If a mother is lying on her stomach, the puppies basically have free access to milk, but, if the mother is standing up, then the puppies have to work to get it," said co-author Robert Seyfarth.
"A hypothesis might be that you have to provide your offspring with minor obstacles that they can overcome for them to succeed later in life because, as we know, life as an adult involves obstacles."
Parallels could certainly be drawn to human behavior, as experts warn that "helicopter parenting" can be detrimental to kids' well-being, while fostering independence and grit in the face of adversity have lifelong benefits.
When it comes to dogs, researchers are continuing to study how a mother's anxiety might be passed on to her puppies.
Are the overcoddled puppies picking up on their mother's anxiety? Are they reacting to their upbringing somehow? Or are they inheriting genes that make them more fearful?
"With mothering, it seems like it's a delicate balance," said Bray.
"It's easy to be like, 'Oh, smothering moms are the worst,' but we aren't exactly sure of the mechanisms yet and we don't want to tip too far in the other direction either."