A very small part of the population has what is commonly called “perfect pitch.” More properly known as “absolute pitch,” individuals who possess it inherently know what pitch is being played and can sing any give pitch without a point of reference at any time. It offers an advantage to musicians, however our current understanding strongly suggests that this is a skill that needs to be developed before the age of 9 and can’t be learned as an adult.
That hasn’t stopped a lot of folks from trying to train adults to acquire perfect pitch. A lot of these are probably scams, although some may be good ways to teach ear training. One common approach is to train your sense of pitch memory so that you always have a point of pitch reference.
A recent study investigated this by training subjects to their working memory for pitch recognition. After going through a training program that offered corrections and reinforcements, subjects scored significantly better on tests where they were asked to recreate and label pitches. Lead researcher Howard Nusbaum said:
This is the first significant demonstration that the ability to identify notes by hearing them may well be something that individuals can be trained to do. It’s an ability that is teachable, and it appears to depend on a general cognitive ability of holding sounds in one’s mind.
I agree with what Richard Moss wrote in the same article. There is a pretty vast difference between the perfect pitch abilities of someone who acquired it in childhood compared with those of individuals who have developed it in adulthood. Nusbaum, et al, seemed to acknowledge this in their article abstract, noting that “the performance typically achieved by this population [acquired at adulthood] is below the performance of a ‘true’ AP possessor.”
Take a look at the following graph, from Absolute pitch: perception, coding, and controversies, by Daniel J. Leviton and Susan E. Rogers.
It would also appear that developing true absolute pitch as an adult is extremely rare, in spite of all the courses and effort folks often take in developing it. That’s not to say that working on your pitch memory is bad, any ear training is good for your musicianship. I would recommend, however, that you focus your ear training practice on skills that are practical for what you want to do. I would argue that it’s more important to focus your effort on pitch relationships, that is to say, relative pitch. Even folks with perfect pitch have to practice this and spend time on it, and this skill is much more critical than being able to recognize a pitch without a point of reference.