In a completely lost position do chess engines attempt to bait their opponent into mistakes, or just play for the longest survival?

Question

Essentially, do Chess Engines acknowledge that their opponents might make "flawed" moves? Or do they always assume absolutely perfect play.

More specifically, if an engine has a choice between 2 moves and one of them is:

• Mate in 5, with perfect play, all of which is completely obvious

and the other is

• Mate in 4 ... but only if the opponent does something superficially counter-intuitive. And if they do the superficially obvious thing then you can actually escape the Mating sequence into a not-directly Mated position

If you assume perfect play, then both positions are a loss, and I assume that engines are "taught" to pick the longest game if all games are lost.

But I would argue that if you believe the game is lost either way, you might want to pick the line with highest chance of an error, instead?

Do engines do that?

Answer 1

Chess engines always consider the "best move" possible for both side. What the "best move" means, is the best move found from the engine according to its evaluation function, selection algorithms, pruning and so on. But no, they don't have a sense of "possible error". Because engine evluated a checkmated position with a score plus the distance-to-mate, every engine choose the move that leads to the longest line possible to be checkmated as it will have the highest score found. Assuming no bugs in the engine, of course.