Making biscuits for a living is surprisingly hard work. One of the important isssues is how long will the product stay fresh, whether in a sealed packet on a supermarket shelf or once the packet has been opened.
Here’s a way for manufacturers to quantify the freshness of their product as a function of time, humidity, sugar content or whatever.
It’s well known that the one’s eyeballs vibrate, when crunching food, in ways that the visual system itself can’t compensate for. This effect is made visible when eating a biscuit in front of your computer monitor (generally bad for the keyboard).
The screen image will appear to jump around with an amplitude and frequency largely determined by the crunchiness of the food and the frame rate of the monitor (similar things happen to horn players apparently…Horn players who eat biscuits simultaneously are an endangered species).