Well it has been a massive question from the side of the every second parent of this generation- "Why is my child dull?" There are thousands of mere answers for such a question. But there's nothing satisfying. The reason lies just right in everyone's nature and being.
Rather if we start up from the root of the answer, then there's something called slothfulness. Whenever this word slothfulness' strikes our ear drum or is signalled by our retina, there's a scenario of laziness created on the canvas of our cogitations. Well the word truly synonymifies laziness, but the wrong impression that we have on our mindset about laziness is that we feel that it is the quality of being unwilling to do something that costs energy and in simple words it is just having a feeling of not moving any body part and being in a rest position. So in short we feel that it is an unwillingness to do physical work. Well, if we add up some extra cheese to the assumed definition of laziness, then it clearly points out that not only are we humans slaves of physical indolence, but mentally too we experience slothfulness at times.
So laziness is among the virtues that everyone bears. Though a negative virtue. But even after knowing that laziness is one of the virtues that has no pros, we still tend to bear the cons of the feeling. So, this holds correctly in case of students. Well, a child is never ever a dull one. But its laziness that retards him from studying and the consequences include the scoring of less marks, millions of complains from the teachers and all crap.
So as we all know, that God has gifted us with alike brains, its upto us, how we use ours. If we are given a mass of clay in our palms, and asked to make whatever we can, then no two people are going to make the same things. Some will just roll it over and make a ball. Some might make long snakes, yet others might make a small beaded garland out of it. So what is made out of the same kind of clay depends on how the person folds it. The same amount of clay was given to each one, yet none of them made the same things. Similarly, all our brains have the same capacities, all of us are given the same kind of brains, but its our wish how we fold it and use it.
There's something called hard work, that leads to success. But there are two kind of urges in every human. 1. Sit and always be in in an illusion of being in rest. 2. Work the hardest to achieve rest of soul, i.e., success. Though each one have the 2nd urge, but it depends upon the concentration. If 1st is in concentration 2nd will lose its hold and if 2nd is in concentration then 1st would be there but definitely 2nd will dominate the human.
So the dull ones, as some people call, aren't dull but they have a concentration of the 1st urge. But the day they will realize that they are in an illusion of being at rest, and that the true meaning of being in rest is not laying down doing nothing but is being in the rest of soul, they will wash off the 1st urge out and develop the positive virtue of hard work. So on that day, both the mental and physical indolence would be eliminated. And the dull and the weak ones, would emerge out of the shell of illusion and step into the realistic world of truth and rest of soul. And that will be the day when the world would thank for the person's presence and the Earth would boast of for beholding the person's life during the conversation with the other planets.