Chris Chatham at Developing Intelligence reports a study in which a greater amount of working memory seems to hamper learning rather than aid it.
The link takes you to the full post, but here’s one of the highlights:
…subjects who were able to remember more letters [in the experiment’s tasks] actually took longer to learn the complex categorization rule! (Here, “learning” is defined as the number of trials until they got 8 trials correct consecutively). This result was reversed for the simpler rule, such that subjects with better working memory learned that rule more quickly. Furthermore, memory scores were unrelated to perceived pressure, providing preliminary evidence that higher scores are not merely related to motivation.
“Simple categorization” in this case was classifying objects according to one dimension — e.g., if the dimension were shape, you might identify all the circular things. “Complex categorization” would involve two out of three factors — e.g., squareness, redness, largeness.
Here’s a related post by Kumar Narayanan summarizing some thinking about working memory.