Effect of Heat on Active Force JND
(Summarized, request for actual paper)
Introduction
There is a concept in psychophysics called “JND”. Essentially speaking, it’s the smallest amount of change required for the change to be perceived. In the case of forces, this value is 7%. Essentially speaking, a change of 7% is required for a new force to be felt.
That is, if a person’s finger was subject to 10N, they wouldn’t be able to feel the difference between 10N and any value of force below 17N.
This value plays a critical role in precision activities. For example, when cutting something, if the surface being cut does not provide a high enough resistance, one might cut too deep. A good practical scenario would be surgery.
I wanted to find out if the JND can be decreased, making one more sensitive. Hence, I began researching on whether heat can reduce the JND.
The Experimental Protocol
The experimental protocol was simple. A subject would be made to apply force on a sensor till it meets a required value. The subject will then repeat the process. The second value may be the same, higher or lower. The subject will know when they have achieved the target through a visual stimulus (a point that moves up and down till it meets a line). In order to remove visual bias, the target line will not adjust itself based on the amount of force required.
The subject will then repeat the same experiment but this time the temperature of their fingers will be raised by 7C through an IR lamp. The results were then used to find the JND at the 2 different temperatures.
The Results
Without beating around the bush, the JND decreased from 7% to 5.5%, which is a significant improvement. The exact details of the experiment and calculations can be found on my published paper. You may contact me for a pdf of the paper if you do not have access.
Kumar, M., Anbuchelvan, A., & M, M. (2019). Effect of Heat on Active Force JND of Active Hand.
Recent Advances in Applied Mechanics, Springer 2022.
https://doi.org/10.1007/978-981-16-9539-1_32
