Human Sense of Smell Is More Sensitive Than You Might Think

ScienceDaily has brought us yet another interesting article related to the National Science Education Standards Life Science Content Standard. My guess is that middle school teachers’ and students’ olfaction capabilities might be a bit superior to the general public’s, given my personal experience in teaching middle school! Nonetheless, scientists from Northwestern University’s School of Medicine report that imperceptible levels of scents affect our judgment in unconscious ways.

The article, Subliminal Smells Bias Perception About A Person’s Likeability, does not explicate the researchers’ questions or hypothesis, but inference indicates their questions were: What concentration levels of scents can people consciously detect? How does scent affect human judgment of the likeability of other humans?

Three scents were used at several levels of concentration, from imperceptible to definitely perceptible. The scents were: “lemon (good), sweat (bad) and ethereal (neutral). . . . Study participants were informed that an odor would be present in 75 percent of the trials.” After participants sniffed a sample, they were shown a photo of a human face with a neutral expression and were asked to rate the person’s likeability along a six-point scale. Though no details are given on how the data was analyzed, the lead author is quoted as saying,

The study suggests that people conscious of the barely noticeable scents were able to discount that sensory information and just evaluate the faces. It only was when smell sneaked in without being noticed that judgments about likeability were biased.

How to Turn This News Event into an Inquiry-Based, Standards-Related Science Lesson

Do your students participate in a Science Day competition or activity? Then you know how hard it can be to help students find a topic they can relate to and apply the methods of science. Sharing this article with your students and accompanying it with a discussion of the methods of science used here might just be the perfect bridge to help your students find an accessible topic. Since particular sample sizes and data analysis methods are not described in the article, you and your students could brainstorm a variety of possible approaches.

You could follow up by going through your local library’s electronic periodical data base to find the researchers’ original report in the December 2007 issue of Psychological Science, “Subliminal Smells Can Guide Social Preferences” by Wen Li, Isabel Moallem, Ken A. Paller, and Jay A Gottfried, and sharing with your students the methods these researchers did use. A discussion of the pros and cons of their methods as compared to those brainstormed by your students could round out your lesson.

The ScienceDaily article can also be used as an introduction to a unit on the senses (i.e., structure and function in living things) or on regulation and behavior, both topics within the NSES Life Science Standard. After sharing the article with students, ask: From an adaptive perspective, what value might there be in this phenomenon of imperceptible levels of scent causing unconscious behavior? Are humans the only organism likely to display this trait? How do you know?

Here are some additional resources that are part of the Middle School Portal 2 collection to facilitate your instruction regarding structure and function in living things, olfaction, methods of science, and regulation and behavior: Structure and Function in Living Systems; Enose Is Enose Is Enose; Discovery, Chance and the Scientific Method; Regulation and Behavior.

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This post was originally written by Mary LeFever and published December 13, 2007 in the Connecting News to the National Science Education Standards blog. The post was updated 4/23/12 by Jessica Fries-Gaither.