I used to believe that learning to draw generally made me a better observer. I no longer believe this.
In a literal sense, learning to draw does improve visual observation, because it improves one’s ability to appreciate shape, style, value, intensity, hue, and other visual characteristics. After sketching something in the field, especially from multiple angles, one gains an almost eidetic memory of it. And learning to draw what is seen helps to break the tendency to stereotype.
However, I no longer believe (in my own case, at least) that this improvement transfers to anything other than visual observation.
I arrived at this conclusion about two weeks after starting guitar: I was driving home from work one day when I realized that my musical taste had changed: in the span of two weeks, I had gone from listening indiscriminately to whatever was on the local/satellite radio to listening almost exclusively to classical and bluegrass music on Pandora, which I previously couldn’t even tolerate! Now, I can listen to almost anything and experience a much greater level of appreciation and understanding than before I started learning an instrument.
In hindsight, the reason is clear: by attempting to play an instrument, by struggling to produce musical sounds, I began to appreciate what goes into creating music. In some sense, I was going through the same struggles the musicians on the radio went through years or decades ago, and I suddenly understood. Classical music, bluegrass, and other styles were no longer foreign but fascinating. I finally had a useful frame of reference.
Learning to produce music is all about observing deeply, about paying attention, and about letting yourself experience its beauty.
The same experience is true of drawing, painting, medicine, mathematics, computer science, travel, parenthood (so my friends with kids say!), or other fields of endeavor. It’s often impossible to genuinely appreciate something until you’ve thoughtfully “been there, done that.” You begin to understand, and this improves your ability to observe.*
*Update 6/14/15: could this phenomenon be related to mirror neurons?