I attribute that to the lack of boredom in young people. When I was young I was bored at least from time to time. This led to doing mischief but also to use the brain and invent something entertaining to waste time.

Now distractions are all around us (play stations and TV on demand) or with us (smart phones). No more need for being imaginative.

There is also this interesting correlation of declining crime rate which can be attributed to kids wasting time with play stations rather than hanging out in the street.

have discussed this with close friends. In the past we perceived that and considered declining intelligence as an assumption, with recent articles like that it seems to be a fact.