Why I no longer use shirt pockets

During the years I spent in mandatory military service, I always kept a small notebook and a pen in the left pocket of my uniform shirt. Nowadays, I virtually never put anything in my shirt pockets, even though I still carry a notebook and a pen and frequently take notes. That is because now that I'm a civilian, I own and wear many different shirts. Some of them have breast pockets, some don't, and some have a pocket only on one side. Some of the pockets have flaps and/or buttons, some don't.

When I wore a uniform I could always count on having a left breast pocket with a flap that can be buttoned, so whenever I wanted to fetch the notebook and/or pen I just had to reach into a fixed position, a gesture that was ingrained into my muscle memory. In civilian clothing, this is not so easy - there are many different arrangements of pockets. When I want to fetch my pen, I have to take a second to try and recall where the pen goes in this particular outfit, or else pat every single pocket (and a few positions where this outfit doesn't have any pockets but many others do) and try to feel which one contains a hard, pen-shaped lump.

Effectively, the pockets become a co-modal interface for retrieving the pen and/or notebook:

A human-machine interface is co-modal with respect to given end-state when

(1) the gestures required to establish the desired state depend on properties of the interface's initial current state

(2) that the user wouldn't naturally pay attention to.

The Flipside of Interface Modality

Well, I can't be bothered to memorize a new arrangement of pockets every single time I change clothes, and I also don't want to be habitually self-frisking in public, so I had to find some way to have a consistent arrangement of pockets even as a civilian. So I bought three pairs of the same cargo trousers, and used them nearly exclusively for five years (except for formal occassions where cargo trousers wouldn't be acceptable and clothing-related discomfort is just a cost of doing business).

Even after I wore them threadbare, I delayed replacing them for as long as possible, dreading the transitional period when I'd have to un-learn my existing muscle memory and habituate myself to a new arrangement of pockets. Turns out I didn't need to fear: the maker of those cargo trousers is in the business of workwear, not fashion. Which means that they don't throw out their entire stock and replace it with new designs every season. When they have a design that sells well, they keep making and selling more of it, for years and years. Even though five years have passed, I could still buy the same cargo trousers I'm used to!

This time, I got five pairs.