Quantifying gustatory sensitivity using signal detection theory
through its collaboration with the SERC Pedagogic Service.
In this lab, students explore the complex relationship between sensory stimulus and perceptual experience. This lab demonstrates how "noise" in the perceptual system, individual variability, and sensory adaptation influence perceptual judgments. Students serve as both experimenters and subjects to collect psychophysical data on gustatory detection of sugar in water, and assess how these data change due to sensory adaptation when extremely sweet water is also tasted. Students explore individual differences in sensitivity (d') and criterion (Beta), represent their results visually using receiver operator characteristic (ROC) curves, and complete a group report describing their results, evaluating the methodology, and identifying possible real-world applications for signal detection theory.
Context for Use
Description and Teaching Materials
- Instructor assigns relevant readings on signal detection theory including introducing the concepts of d', Beta, and ROC curves, and provides a brief lecture on the material.
- Students are assigned to pairs and given a jug of plain water and jug of sugar water (approximately 4 tsp/gallon), along with small tasting cups and pipettes
- Working in pairs, one student (the experimenter) gives "blind" samples via pipette to the taster in randomized order. The taster responds whether they detect the flavor (is there sugar in the water?) and the experimenter records the response as a hit, miss, false alarm, or correct rejection. Students take turns in the roles of experimenter and taster.
- After both students have served both roles, the process is repeated, but the second time, the students intersperse sips of very sweet water (1 cup/gallon).
- For both team members in both conditions, students calculate the probability of hits, misses, false alarms, and correct rejections. From these, they calculate d' values (indicating perceptual sensitivity).
- Students create ROC curves representing their results, and complete a group report detailing their findings.
Instructions for data collection (Microsoft Word 2007 (.docx) 98kB Sep17 12)Group report (Microsoft Word 2007 (.docx) 68kB Sep17 12)
Teaching Notes and Tips
In a later Sensation & Perception lab, we will conduct tongue-staining in order to determine the density of fungiform papillae on each student's tongue, and measure their taste sensitivity using PROP tasting strips. The data from this signal detection lab may be used to correlate individual differences in d' with individual differences in papillae density and PROP bitterness ratings.
This lab could also easily be adapted to auditory perception. In that case, students could be presented with files containing no sound and files containing a very quiet tone. Adaptation could be achieved by completing testing after being in a quiet room vs. a noisy classroom.