The I-type earns from expertise and knowledge. That person has academic knowledge and as he or she moves up the career ladder, this specialized knowledge becomes so precious, everybody relies on that expertise. The person feels powerful, valued and enjoys clear role and purpose in the organization. Typical I-persons are specialized surgeons, lawyers, accountants or financial experts. They build up a knowledge monopoly and this makes the position difficult to reach for others. Experience and dedication created the value offer.
Now let's look at the T-type. How does that professional creates value? In this case the knowledge comes from relationships. Rather than deepening the knowledge in one field, the expertise is to create valuable relationships that will complement the basic speciality gained during the studies. Generalists know a little about everything while specialists know everything about nothing. So goes the saying.
Now back to reality.
For an I-type professional the deepest knowledge is not valuable without a sense of reality. And the best way to have a grounded opinion is by understanding the views of others. Hence better know a little from the other areas and functions to leverage a speciality and add value to the team.
The T-type professional on the other hand must be careful to avoid only building relationships without content or with knowledge too superficial to be of any value.
Because innovation comes from blending knowledge. Therefore both I-types and T-types must focus on becoming a bit more knowledgeable in the content in other domains. And better go deep and in-depth in a few unfamiliar areas than remaining superficial.
How old you are, does not matter, if you wish to boost your career, keep learning - in new areas - because it is the variety that sparks innovation. And nothing adds more value than innovation!
A T-type with genuine interest to put the dots on the Is of colleagues is the most valuable kind of person in any organization!