Rossolimo : why does Black recapture laterally, ie 4 Bxc6 dxc6 ?

Gawain Jones, in "How to Beat the Sicilian Defense..."(2011) correctly states the Rossolimo ( B31 ) mainline is 1 e4 c5  2 Nf3 Nc6 3 Bg5 g6 4 Bxc6 dxc6 . He says that capturing laterally ...dxc6 is played over twice as often as capturing medially ...bxc6.

Databases confirm this. However all databases I've examined give White a greater percentage of wins for lateral capture.

eg. chessgames.com  4 ...dxc4 White wins 47% Draws 34.6%, Black wins 18.4%

4 ...bxc4 White 40.1% Draw 35.7% Black wins 24.1%

It passeth all understanding why Black makes a counter-intuitive move, lateral recapture, when all data shows Black scoring worse with this.

Any help appreciated.

On chess.com's masters database it gives 48/21.5  (1859 games) for dxc6 and 50/24 for bxc6 (670 games)

So it looks like the former according to this is actually played ~3x as much.

Never the less you ask a good question and it was something that occurred to me today. Black gets a full bodied pawn centre and it seems white at some stage will play c3 and d4 undoubling black's pawns and leave him cramped but with the two bishops.

Fischer won a nice game as white in his "comeback " against Spassky. Spassky captured towards the centre...

Although as white I've been glad to see dxc6 rather than bxc6 as I prefer a static Nimzo style game to a dynamic pawn centre type of game.

In the 3. ...g6 line, the reason Black recaptures with dxc6 most often is because it gives him greater control of d4. If he captures with bxc6, White can quickly get in d4, usually through the move order 5. 0-0 Bg7 6. Re1 Nh6 (6. ...Nf6 7. e5 is bad for Black) 7. c3 0-0 8. d4, when White has strong central control and Black's h6 knight looks silly, but Black has the two bishops and a fairly solid position. dxc6 makes it much harder for White to get in d4 (and to call these positions "Nimzo-Indian" like is nonsense. They both feature doubled c-pawns, but that's where the similarities end.)

The other thing to consider is that Black has the Bishop Pair.  Just like in the Exchange Ruy Lopez, when White trades here on c6, the advantage to taking with the d-pawn is it opens up both Bishops for development.  With 4...bxc6, as pfren mentioned, there's the lack of mobility, but there also inlies the problem of making use out of both Bishops.  At least one of them will most likely become extremely inactive in the 4...bxc6 line.

I thank all of you for your kind help.

IM pfren : what do you mean by "bih center" ?

clunney "it gives him (Black) greater control of d4". Lateral recapture does half open the d file, enabling Black's queen to attack the d4 square. But Black is always "a day late & a dollar short" and never has full control of d4. White can move c3. The best Black can do is an equal pawn exchange on d4, which can leave White a pawn center.

ThrillerFan : I appreciate your comments re bishop mobility. But medial recapture immediately opens the c8-a6 diagonal for Black's queen bishop. And opening the other diagonal requires a single pawn move.

Admittedly mainline is lateral recapture. As in my original post I have trouble with this considering results. I examined four databases ( I mentioned one previously ) and calculated White's 'expectation', ie White's percentage of wins plus half the draws. With lateral recapture all databases yielded a higher expectation for White than medial recapture. The better result for Black with medial recapture seems true across all Elo ratings, ie < 2200, 2200-2500 and > 2500.  Please examine this with databases you have available. If this holds up, why is the prefered line lateral recapture ?

Finally I analyzed the positions after the 9th White move in all four common lines ( two lateral and two medial recapture ). I realize analysis is a poor way to study openings. I used three engines Stockfish 5, Houdini 2.0 and deep Hiarcs. Went as deep as 26 ply. Results vary, but medial recapture tends to have lower position scores ( lower = better for Black ).

Again thanks for everyone's kind assistance.

Day late and a dollar short to prevent d4? If White tries to force d4 by playing c3 in the dxc6 Rossolimo, Black has ideas like c5-c4, which permanently shuts down White's d4 dreams and creates a hole on d3, as well as keeping White's knight off c3.  This c4 idea is not possible in the bxc6 Rossolimo because Black can't hold c4 with b5, since the b7 pawn has migrated to c6. White can try playing d3 first then c3, but this is slow. The point of dxc6 is it's the only way to hold the d4 square after playing 3. g6, unless Black wants to put a pawn on e5, which makes the g7 bishop look stupid. dxc6 also releases the bishop on c8, where it can come to g4 and fight for... d4. Hence why White nearly always plays an early h3.

Try and find some master games in the dxc6 Rossolimo featuring an early c3 and d4.  It is almost unplayed, because it does not work.

clunney "Black has ideas like c5-c4, which permantently shuts down White's d4 dreams...".

You're right. I played it out. Thanks so much.