Torvald. I don't think these researchers have successfully acquired absolute pitch, so their research seems to appeal to ignorance. But then I'm not sure if everyone can develop perfect pitch (you can, for example. read a bit about the role of tonal language acquisition on perfect pitch). I myself was exposed to C-major scale when I did some piano lesson at age 10 (and then I quitted fairly quickly as the teaching method was just unbearable). I know I have attained a rather sophisticated level of perfect pitch and that's pretty much a done deal for me (for now at least), but then there are different levels of perfect pitch as well (atonal vs. tonal, pitch class -> symbol vs. symbol -> pitch class), so the pursuit towards better ears never ends
In one word, the acquisition of perfect pitch relies on automatization
, or mechanization of simple mental processes. But automatization is best achieved via a regular, controlled exposure to cognitive stress (neural hormesis?).
When I was starting, I had to learn to associate pitch with their corresponding solfege syllable. I chose to use a fixed-do solfege (i.e., do/di/re/me/mi/fa/se/so/le/la/te/ti). And that proves to be a very right decision, as I can now transcribe songs in my head.
Back then I had to write a program to randomly generate real sounds, from sine wave to piano to cello/violin and harpsichord. Nowadays web applications related to this are everywhere.
If you are starting, it's advisable to work with only 5 pitches or so, and just spend some time listen attentively to them (piccolo works great, because of its piercing timbre, and let the sound sustain a bit!), but do listen with an absence of thought. The idea is that no association should be done until the sounds become sufficiently salient.
Now that you talk about that. I had also devised a method to assimilate accent which is based on rehearsing syllables slowly and attentively, in your mind! And now I see that this does indeed have deep root in hormesis (had those concepts before knowing the word