The Answers: Question 9

9. Imagine that humans suddenly develop a new sense, the ability to detect the age of an object or organism by touch. It is first detected in a seamstress who can reliably tell apart vintage silk dresses and modern replicas made with new silk fabric although they seem to be identical in appearance, materials and construction. Many or most other humans develop this sense, and are able to sort almost everything—carrots, cars, castles and cats—by age. Imagine that you are pioneering the psychophysical research to establish the properties of this new sense. Describe the procedure of a useful experiment you could conduct and what possible pattern(s) of results you would expect to find. [5]

The proposed study design should use one of the standard psychophysical methods for investigating a sensory modality: method of constant stimuli, method of limits, method of adjustment, magnitude estimation, or cross-modality matching. A good answer should demonstrate a sound understanding of research design, perception and the specific method. Does it have a clear hypothesis and does the experiment test it? I’d hope to see designs that take into account both animate and inanimate objects. The study design doesn’t have to cover everything but it should be clear that the student understands what slice of the phenomenon this experiment would investigate. A top-notch answer would talk about determining the Just Noticeable Difference (JND), an absolute threshold, or a two-point threshold of this mysterious new sense.

Imagine that this sense is attributed to a new sensory receptor—the age-o-tron—that seems to have four types (fast- and slow-adapting, with large or small receptive fields). What type(s) of stimuli do you hypothesize would have the strongest effect on each age-o-tron, and why? [8]

This question calls for speculation and reasoning. I would expect to see a 2X2 table here, and student could earn some marks just by recognizing that the set-up is analogous to the mechanoreceptors, which are touch-sensitive cells in the skin that come in the same four types. What might the effect of a large receptive field be on an age-o-tron? What would distinguish slow- from fast-adapting? For example, an age-o-tron with a small receptive field might be able to discriminate, for compound objects, the pieces of different ages. What a great way to detect hidden repairs on a used car!

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