The Nose Knows: The Unique Role of Smell in Memory

A few weeks ago I wrote about the tendency for immigrant cultures' culinary traditions to outlast their language (if you missed it, you can read it here). At the time I focused on some of the cultural factors, particularly here in the U.S., that could be responsible, but today I want to propose a more psychological hypothesis. The idea is this: memories associated with smells (and potentially taste, although there's far less research on that) are uniquely emotional and long-lasting. I'll get into why that is in a minute, but I wonder if the strength and emotional content of these odor memories (and the dishes that generate them) make them more likely to be passed down from generation to generation. 

Is it time for dinner yet?

Is it time for dinner yet?

I probably won't ever end up actually testing that hypothesis, but my scientific fascination with smell and memory goes way back. The first science experiment I ever designed investigated the effect of different cues (smell, sound, and a control, I think) on the memory for food location in mice. I ran the experiment for my 9th grade biology class, and at the end of it my teacher told me that it was more of a psychology experiment than a biology experiment. Humph...

In any case, I recreated a pretty solid finding (in both psychology and biology!) that odors make highly effective memory cues. Studies like this one and this one, which asked adults to describe memories associated with either words, pictures, or odors, found that the memories elicited by odors tended to be from childhood (10 and earlier) and to evoke a stronger emotional response. Neuroimaging evidence supports both these claims. For example, another paper by scientists at Stockholm University finds that memories cued by odors, as opposed to words, elicit more activity in the brain regions associated with emotion and vision processing (the latter is important because more accurate memories tend to reactivate the same areas that were engaged during the original experience; that is, there's a reason why certain memories may cause you to feel as if you are re-living the experience). As far as the association with earlier memories, findings by Yeshurun and colleages in Current Biology (sorry, I really can't let 9th grade go) found that the first exposure to smell cues, but not sound cues, elicited activity in the hippocampus (a part of the brain crucial for memory) that predicted later performance on a memory test.

Is this garlic bread? I frickin' love garlic bread!

Is this garlic bread? I frickin' love garlic bread!

So, memory for smells are stronger and more emotional, and they tend to be formed early. And when I say early, I mean early. In one study, infants who were exposed to the smell of chamomile during breastfeeding (via a nipple balm prescribed to the mother) showed a preference for objects chamomile-scented objects during tests at both 7 and 21 months. Even cooler, another study that tracked exposure to garlic during pregnancy found that at ages 8-10 children who had been exposed to garlic in the womb preferred garlicky foods more than infants who had not had prenatal garlic exposure. 

To me, all this suggests that we form strong, early attachments to the foods that we grow up with, and consequently we may be more likely to pass those on to our children and grandchildren than the words that we use to describe those same foods. Even if I'm wrong about the reason, it's kind of neat to think that in passing down these dishes we are recreating some of the same smells and experiences that our great-grandparents may have made in their own kitchens.

What do you all think? Do you prefer the cultural explanation from the last post, or the psychological one I presented here? Can you think of particular smells or foods that bring you back to your childhood? One of my favorites is pasta e fagioli (if you've been reading the blog for a while, you may be noticing that I was a big soup kid). It's a simple dish, but one I will always enjoy, as much for the memories it brings as for the the starchy goodness.