While actualization at any level involves mental development to various degrees, one can decide to choose mental actualization while keeping a low profile on the others. 'Nerds' get their name from exactly this type of behaviour. Here, I would like to distinguish between a 'nerd' and a 'couch potato'. While the nerd is actively involved in his/her actualization, the couch potato has fallen into passivity, with only a minimum of learning, if any.
While scientists tend to make the top of this list, most academics fall into this category. Most of them have some actualization at other levels as well. The true hybrids work at two or more levels simultaneously. The most common combination is that of emotional and mental, as these are almost inseparable functions of one mind. I mentioned artists, but they also include inventors and politicians. In fact, I believe that a good balance between the four levels of actualization makes for more capable and versatile people. That is probably why you may find professionals spend their week-ends sailing or skiing or playing other sports or dancing, acting, or painting.
Coming back to the handicap theme. Ever noticed that people often choose a profession in an area where they need to develop most? We get curious about certain things and go on from there. We also tend to be inventive where we are lazy. e.g. 'Engineers' like to go to considerable mental effort to avoid physical energy. This makes them creative and inventive and gives them the natural aptitude to think about improvements. In fact, one can only look for improvements if one is unhappy with the status quo. Complacency may make for a peaceful mind, but it does not make one looking for improvement, therefore not for invention. One needs the feeling of 'unhappiness' as a driving force.
Again, as much as 'happiness' is an attitude, so is 'unhappiness', so is 'complacency'. But what is attitude? This brings us to the next level of actualization: