Insomniac Intelligence: "How The Pinkie Sense Works" · 6:56am Feb 23rd, 2013
Welcome to Insomniac Intelligence, where I share any realizations I've made or mysteries I've solved thanks to my mind wandering due to being tired! 
Today, I'm covering the Pinkie Sense. A topic that has confused many; even Twilight Sparkle couldn't figure it out. But I believe I have a reasonable, scientific explanation for how it works that isn't just "Pinkie Pie randomness".
You may or may not know of extrasensory perception; also known as ESP or a sixth sense. To quote Wikipedia, as I have difficulty wording it myself: "Extrasensory perception (ESP) involves reception of information not gained through the recognized physical senses but sensed with the mind. The term was adopted by Duke University psychologist J. B. Rhine to denote psychic abilities such as telepathy, clairaudience, and clairvoyance, and their trans-temporal operation as precognition or retrocognition." So, essentially, it allows for psychic-like abilities with the mind, including precognition - more or less a future sight.
As ESP is a real thing that some humans actually have, it would not be outrageous to suggest that Pinkie has ESP or a form of it. However, instead of having mental precognition - basically seeing the future in her mind - she has physical precognition. Her various twitches and combos are physical ESP predicting the future; she can't tell exactly what's going to happen as it's only body movements, but she can memorize what twitch happens before what event and use simple deduction to figure out what it means. For example, twitchy tail; she could have noticed that her tail twitched right before an apple fell in front of her, and later on it twitched again before a bag of flour fell out of the cupboard. She'd realize that whenever her tail twitches, something falls.
Why is her ESP physical, though? Why wouldn't she just be able to see visions or something?
To put it simply, she's too random. If she did see visions - which she might, for all we know - she'd probably ignore them. Being an earth pony, however, her physical capabilities are higher than that of a pegasus or unicorn; plus, her rather odd abilities (growing fingers, slowing gravity, pulling stuff out of nowhere, etc.) show that she obviously possesses a little bit of magic. But she doesn't think about doing things, she just does them. Anypony else would spend time thinking about how to do something, but Pinkie just does it because she knows she can. Her ESP is physical because her physical body is apparently flexible enough to perform those various twitches and combos without hindering her too much, and because her inner magic and randomness allow her to channel things through her body before her mind - performing actions without thinking about performing them. Thus, before a vision can reach her mind, it ends up mixing with earth pony magic and turning into a twitch-a-twitch-twitch.
In other words: precognition + earth pony magic + Pinkie-don't-care attitude = Pinkie Sense.
The wording for this probably doesn't make a lot of sense because, as the title states, I'm tired. The theory, though...what do you think of it?
...... Wow. Ok, heres how we solve world hunger, no more coffee untill the scientists figure out how to clone stuff. People always get good ideas when there tired.
Huh... I've tried finishing some long-term projects when I'm tired.
... Didn't quite work out that well.
857452 The weird part is that after I wrote this, I went and managed to get some sleep. When I woke up, I didn't remember any of this aside from "I made a blog post about how the Pinkie Sense works...something about channeling something something earth pony..."
So it's a good thing I wrote it down.