Category Archives: hearing

The Cat in the Hat in the Amniotic Sac: What Can Sucking Tell Us About Hearing?

Cat in the hat What's with the feline in the millinery?  As with yesterday's post, try not to shoot the blogger if you've already heard this one. It's an old study (early 80's – never mind that I can remember the time…just barely I'll have you know), but the media has gone wild with it ever since it first came out. I just could NOT think of a week of posting on methods in infant research without mentioning it. What about that title? Gotta love it!

This study used sucking to shed light on prenatal hearing.In earlier work, the researches had determined that very young infants would adjust their sucking rate to be rewarded with hearing their mothers voice (I bet this doesn't happen in the teenage years…but I digress…). Mothers read The Cat in the Hat Story or another one of two other stories to their unborn fetuses, 2x per day for the last 6 weeks or so of pregnancy. Soon after birth, the researchers measured infant sucking when they heard the story they heard prenatally vs. one of the other stories. What happened? The newborns worked hard (sucked faster or slower) to hear the story they heard in the womb – moreso than to hear the other story. By playing with this method a bit more, later work showed that it was the rhythm of the story and not the words that the babies were responding to. BTW, the babies also worked harder to hear mom do the reading over some other female voice reading the same story. This study was a real landmark in establishing at least a couple of things: 1). the state of development of hearing in the womb and 2). how the prenatal environment helps tweek perception. 

If you're now thinking "Wow, amazing how far these researchers will go", consider this: in another (now old) study a pregnant woman was asked to swallow a tiny microphone so that researchers could gain a better sense of just exactly what the baby can hear in there. Can you imagine it? "It's in the name of science ma'am. Please just please swallow the technology." 

So I'm on a roll now. Here's another interesting way that researchers have used sucking. The main question was whether information taken in through one sense (e.g. sight) is stored in such a way that it can be accessed through other senses (e.g. touch). The technical term is cross-modal or inter-modal perception. In one study, 1-month old babies were allowed to suck on either a smooth or a bumpy pacifier – but they were NOT allowed to see it. The babies were then shown two simultaneous pics, one of the smooth pacifier and one of the bumpy one. And guess what? They looked longer at the one they had sucked on but NEVER SAW, as though they recognized it. So what they had taken in through sucking or touch was stored in a more general way, a way that was accessible through another sense, sight.  

Finally, I wanted to briefly mention the use of "geodesic nets" – think "hairnets with sensors" that provide real-time information on the patterns of brain activity as the brain processes something e.g. a picture, a sound, an event etc. The baby wears a get-up like the one shown here. Newsweek Baby brain
It's not painful at all and many babies are surprisingly co-operative about the whole experience. For more on geodesic nets and language studies, put in user friendly terms, try here.

Phew. It's been a whirlwind tour through infant research this week. Now seems like a good time to ask how this stuff is all working out for you. Too technical? Nerdy? Boring? Less on studies, more on parenting connections?  It would be great to hear some feedback. I hope that even if the details were too much or we covered too much ground that you might have gained a new respect for that bundle of sweet-smelling, soft, cuddly goodness. That's one amazing brain growing in there!