Question:
What parts of the body have higher resolution for interpreting somatosensory (touch) information? How does temperature or pain change this resolution?
Materials:
- Erasers
- Round head pins
- Heating pads
- Ice packs
- Optional: markers (can use to visualize resolution of somatosensation of an area on the skin)
Instructions:
- Insert sharp end of 1 pin into erasers
- Insert sharp end of 2 pins into erasers at various distances (2mm, 5mm, 10mm, 20mm, 30mm, 40mm)
- Participant closes his/her eyes and holds out fingertips or forearm.
- Experimenter randomly chooses to gently touch the fingertip or forearm with either 1 or 2 pin heads making sure to touch with both pin heads at the same time (if using 2 pin heads) to eliminate a temporal variable.
- Participant says whether they think the experimenter touched them with 1 or 2 pin heads.
- Experimenter writes down whether the participant was correct or not. The smallest distance between the 2 pin heads at which the participant is consistently correct is considered the threshold distance for that body part.
- Explore with heating or cooling the skin or the pin heads and make hypotheses about how the threshold distance will change, if at all.
- Discuss why certain areas having higher resolution (smaller threshold distances) than others and how experience can change a person's ability to accurately perform this two-point discrimination task.