Chapter 15 Notes

Chapter 15 Notes - June 6 2006 Odors in our world...

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June 6, 2006 Odors in our world Multi-billion dollar industry in perfumes And “under-arm” deodorants. Ditto for mouth-washes Real-estate brokers encourage sellers to have coffee brewing when potential buyers come. Automobile manufacturers now sell and distrubute “new car smell” Overview of Questions Why is a dog’s sense of smell so much better than a human’s? Why does a cold inhibit the ability to taste? How do neurons in the cortex combine smell and taste? Functions of Olfaction Many animals are macrosmatic - having a keen sense of smell that is necessary for survival Humans are microsmatic - a less keen sense of smell that is not crucial to survive Experiment by Stern and McClintock Underarm secretions were collected from 9 donor women These were wiped on the upper lips of recipient women Experiment by Stern and McClintock Results showed that menstrual synchrony occurred since: Secretions from the donors taken at the beginning of their cycles led to a shortened length of the recipients’ cycles Secretions from the ovulatory phase lengthened recipients’ cycles Phermones in the secretions, even though the women did not report smelling them, led to the changes Detecting Odors Measuring the detection threshold Yes/no procedure - participants are given trials with odors along with “blank” trials They respond by saying yes or no This can result in bias in terms of when the participant decides to respond Forced-choice - two trials are given, one with odorant and one without Participant indicates which smells strongest Detecting Odors - continued Rats are 8 to 50 times more sensitive to odors than humans Dogs are 300 to 10,000 times more sensitive However, individual receptors for all of these animals are equally sensitive The difference lies in the number of receptors they each have Humans have 10 million and dogs have 1 billion olfactory receptors Detecting Odors - continued Measuring the difference threshold Smallest difference in concentration that can be detected between two samples This research must be done with carefully controlled concentrations using a device called a olfactometer Research has shown the threshold to be approximately 11% Identifying Odors Recognition threshold - concentration needed to determine quality of an odorant Humans can discriminate among 100,000 odors but they cannot label them accurately This appears to be caused by an inability to retrieve the name from memory, from a lack of sensitivity The Puzzle of Olfactory Quality Researchers have found it difficult to map perceptual experience onto physical attributes of odorants Henning’s odor prism (1916)
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6 corners with the qualities putrid, ethereal, resinous, spicy, fragrant, and burned Other odors located in reference to their perceptual relation to the corner qualities The Puzzle of Olfactory Quality - continued Unfortunately, Henning’s prism has proven of little use in olfactory research Linking chemical structure to types of smells Initial attempts showed difficulties since:
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Chapter 15 Notes - June 6 2006 Odors in our world...

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