Praveen Kumar.. I dunno. The more I think about this the harder it gets to figure out a way of assessing a bowler's intelligence.
On one hand you have guys that are limited by their style of bowling (or even skill) who stick to a plan because they know it works. Is that intelligence? On the other you have guys who bowl a couple of outswingers and then bring one back in who look like they set the batsmen up but really, what they are doing is essentially the same as the other bowler isn't it? Bowling to their strengths, and sticking to a plan formulated based on them. You can argue that knowing, for example, when to bring it back in is intelligence, but it could be experience and just instinct. The lines become hazy.
Targetting specific weaknesses of batsmen (someone mentioned Hadlee kept a diary?), playing mind games, adapting pace, fields, line and lengths according to the situation and conditions are all qualities that I think I've kinda settled on as the ones I'd look for in an intelligent bowler. And like I said before, I think anecdotes are much more important here in determining which bowlers actually had these.
Praveen Kumar puts himself in the game to be considered for intelligence by having variations.
If you have no variations, e.g. you are brent arnel, then you have no business being in a test team to begin with.
Your job as a teenage bowler is to learn variations.
Learn the leg cutter if you can't swing it. But you must learn movement.
As a spinner I had speed variations. And "areas" variations where I would target different areas on the pitch that still required a defensive shot.
The next comment will sound ridiculous or either make my point. But my final variation was patience. Sometimes I would just keep the pressure on and not bowl my quicker delivery at all, or my more flighted one.
While I am blabbing on. I did have different grips as well and could make the ball not arrive to you when you expected it.
Etc etc etc.
When I was 17 years old and had been in the first team training squad since a 13 year old and was an old pro of high school cricket I would take the up and coming spinners aside and teach them how to think.
Thinking begins when a batsman walks out to bat. Before he has faced a delivery you should know whether he is an offside player or an on side player just from how he is holding the bat and his grip.
If you immediately start executing a plan without waiting to watch the batsman get a few confidence building shots away then you are ahead of the game and likely to get him out.
Sadly my spin was quite ****e against top players and they would smash me for six at will as I didn't have any loop. Less intelligent spinners than I were far more successful just because their basic tool kit was better. Against lower grades I was effective.
Loop is probably more important than spin, or at least equally as important.