Singing to children as a signal of attention

The other day I wrote a post about signalling by university students. Signalling is actually very common. Consider this example from a recent research paper published in the journal Evolution & Human Behavior (open access) by Samuel Mehr and Max Krasnow (both Harvard), as described on Science Daily earlier in the year:

A new theory paper, co-authored by Graduate School of Education doctoral student Samuel Mehr and Assistant Professor of Psychology Max Krasnow, proposes that infant-directed song evolved as a way for parents to signal to children that their needs are being met, while still freeing up parents to perform other tasks, like foraging for food, or caring for other offspring. Infant-directed song might later have evolved into the more complex forms of music we hear in our modern world...

Mehr and Krasnow took the idea of parent-offspring conflict and applied it attention. They predict that children should 'want' a greater share of their parents' attention than their parents 'want' to give them. But how does the child know it is has her parent's attention? The solution, Krasnow said, is that parents were forced to develop some method of signaling to their offspring that their desire for attention was being met.

"I could simply look at my children, and they might have some assurance that I'm attending to them," Krasnow said. "But I could be looking at them and thinking of something else, or looking at them and focusing on my cell phone, and not really attending to them at all. They should want a better signal than that."

Remember from my previous post that signals are a way for the informed party to reveal private information to the uninformed party. In this case, the private information is about parents' attention, the informed party is the parent (they know how much attention they are giving to their child), and the child is the uninformed party (they don't know for sure how much attention they are receiving). I also mentioned that in order for private information to be a problem it must result in some market failure. In this case, there isn't a market but there is a failure - if the infant feels like they aren't receiving sufficient attention from their parents, they respond by crying. Nowadays, crying children might be sleep-deprivation-inducing or mildly annoying, but for our ancient ancestors trying to hide from furry saber-toothed death machines, the consequences could be pretty serious. [*]

Now, for a signal to be effective is must be: (1) costly; and (2) costly in a way that makes it unattractive for those with lower quality attributes (in this case parents who aren't paying attention to their child) to attempt. Mehr and Krasnow offer this:

What makes such signals more honest, Mehr and Krasnow think, is the cost associated with them -- meaning that by sending a signal to an infant, a parent cannot be sending it to someone else, sending it but lying about it, etc. "Infant directed song has a lot of these costs built in. I can't be singing to you and be talking to someone else," Krasnow said. "It's unlikely I'm running away, because I need to control my voice to sing. You can tell the orientation of my head, even without looking at me, you can tell how far away I am, even without looking."

Mehr notes that infant-directed song provides lots of opportunities for parents to signal their attention to infants: "Parents adjust their singing in real time, by altering the melody, rhythm, tempo, timbre, of their singing, adding hand motions, bouncing, touching, and facial expressions, and so on. All of these features can be finely tuned to the baby's affective state -- or not. The match or mismatch between baby behavior and parent singing could be informative for whether or not the parent is paying attention to the infant." 

Which seems to suggest that singing would provide a good signal, since it involves a cost, and if you're not actually paying attention to the child it would be difficult or unattractive to put in the additional effort required to "[alter] the melody, rhythm, tempo, timbre, of their singing, adding hand motions, bouncing, touching, and facial expressions, and so on".

Of course, if you use your phone or tablet as a babysitting aid and avoid the singing, it might just be giving the opposite signal.

[HT: Marginal Revolution, back in February]

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[*] Actually, that's not the best example since singing would probably be just as likely to attract the unwelcome attention of a predator as would the child crying, unless you really believe that music soothes savage beasts (it doesn't sooth savage stock markets).