Strange tactics from the West Indies?

In the test against the Kiwis, the Windies are leading by 202 with Gayle on 140 not out, but they're just blocking, playing for stumps. Shouldn't they be going for the runs and trying to set a target for the Kiwis? Particularly as Taylor got a hundred last time and Gayle ahs alraedy hit 6 sixes.It seems that Gayle has no confidence in his bowlers at all.