Learning Objectives
- To understand the distinction between sensation and perception.
- To learn how to conduct a psychometric experiment.
- To practice using figures to visualize data.
Materials
- Whiteboards
- Dry Erase Markers and Erasers
- Paperclips
- Rulers
- Sticky tack
Overview
This lab is aimed at getting students acquainted with how psychologists attempt to measure sensation objectively. Students will be tasked with conducting their own psychometric experiment and plotting a figure to visualize their data.
Time Allocation:
| Activity | Time Allocation |
|---|---|
| Introduction | 10 Minutes |
| Activity 1: Two-Point Discrimination Experiment | 15 Minutes |
| Class Discussion | 5 Minutes |
| Activity 2: Plotting a Psychometric Curve | 10 Minutes |
| Take Home Message & Wrap-Up | 5 Minutes |
| Submission Time | 5 Minutes |
Introduction (10 min)
During the introduction, we will go over the distinction between sensation and perception, as well as to the field of psychophysics. We will also cover some examples on how psychologists can measure sensation, and different tools used in doing so. This will prime students for the following activity, where they will run their own experiment.
Before then, we will have a short introduction also on the sense of touch, so that they are more well suited to formulate their hypotheses.
Activity 1: Two-Point Discrimination Experiment (15 min)
Students will first start by molding the paperclips and preparing their “calipers”.
Ask them to try them a bit on different parts of their bodies and see if they notice any areas with seemingly greater sensitivity.
They will select two areas of interest which will be used in their experiment.
The groups will divide themselves between experimenters and participants. A minimum of two participants should be used.
Participants will have their eyes closed, while experimenters apply gentle pressure in the pre-designated body parts with either a specific opening size for the calipers, or a single point of the paper clip. It is important to tell the experimenters to be unpredictable with which one they use.
Participants have to indicate on which of the three pokes they felt two points of contact on their skin. After every response, a third student should be making a record of their responses.
Repeat this process for five trials. They will then repeat it again for different opening sizes of the calipers, to be able to relate the opening size to the proportion of trials experienced as two points.
Class Discussion (5 min)
Have a quick conversation with students about their experience running the experiment so far, and if they have any initial observations.
Activity 2: Plotting a Psychometric Curve (10 min)
Now, students will use the data collected during the first part of the experiment to plot their own figures.
- On the y-axis, students will have the proportion of “two-point” responses by the participants.
- On the x-axis, the aperture of the calipers.
The TAs should circle around the room, helping groups which are having trouble.
Wrap-Up (5 min):
- Psychophysics is an important field of psychology that attempts to measure sensation objectively.
- Our brain has different allocations for representations of different body parts in the somatosensory cortex. Certain parts of the body, due to a variety of evolutionary reasons, are much more sensitive than others.
- Show them the sensory homunculus and relate to the neuroanatomy lab they did last time.
Final Submission Question (5 min):
- What was your group’s hypothesis for the two-point discrimination experiment? Was it confirmed or rejected? Can you think of why you obtained the results you did? (experimental, or evolutionary reasons).