The point is not really about the difficulty of conversion, but about having to do it at all. Whether hearing about a 1.42m high man brings up a vivid image imm

The point is not really about the difficulty of conversion, but about having to do it at all. Whether hearing about a 1.42m high man brings up a vivid image immediately, or only after conversion to imperial measures. Not unlike how becoming fluent in a given second language means there are no longer any intermediates. Rather than having to think consciously of a certain sentence in your own native language and then converting that consciously to a sentence in the given second language, you can just immediately think of the sentence in the given second language. This happens gradually of course, there are a few length measurements in feet & inches that immediately give me a clear/rich image of the intended length: 6 feet, my own height in feet/inches, etc. However, the set of imperial length measures for which this happens is much, much smaller than that for metric length measures. For instance, I have absolutely no clue how long a yard is, let alone a hundred yards, and how that relates to a mile. Only after conversion, and doing the conversion enough times, will it become clear(er) to me.