system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Whenever I hear a fork scratching the surface of a china plate, my body shudders. What causes this to happen?
gpt
AFAIK, there are 2 different explanations proposed:

- The primate heritage hypothesis:  Hypothesizes that the sound bore some resemblances to the alarm call of macaque monkeys, or it may have been similar to the call of some predator.

- Physical hypothesis: Hypothesizes that the unpleasantness of the sound is caused by acoustic resonance due to the shape of the human ear canal which amplifies certain frequencies, especially those in the range of 2000 to 4000 Hz (the median pitches mentioned above), at such a level that the sound would trigger pain in our ears.