The primary way of learning chess tactics is by repetition, either by repeatedly solving the same problems, or by solving different problems that contain the same or similar tactical patterns.
Cognitive psychologists have conducted many trials of learning by repetition for simple memory tasks, for example: Question: “What is the capital of Denmark?” - Answer: “Copenhagen." The trials show that long term memory retention is poor when the repetitions are closely spaced (often summarised as “cramming does not work”), but improves as the spacing is widened (until the subject completely forgets the previous repetitions). However, when the repetitions are widely spaced, the success rate improves only slowly with each successive repetition. Cognitive psychologists have found that a high success rate is important for maintaining student motivation. Successful repetitions are also typically faster than unsuccessful repetitions, so more successful repetitions can be performed within the same amount of study time.
To get the best of both worlds, it is usual to space the initial repetitions closely, and gradually increase the intervals between each successive repetition. This scheme has the advantage of ensuring that a high success rate is rapidly achieved, and is sustained or improved upon as the repetitions continue.
Cognitive psychologists have conducted trials comparing the long term memory recall achieved by repetitions at increasing intervals with the same number of equally spaced repetitions. The trials with equal intervals have often done slightly better - but equal intervals are possible only if the repetitions have a fixed end point - which will not be the case if the information has to be retained indefinitely. Nonetheless, this is still a useful result, as we shall see later.
These results form the basis of many practical learning systems, notably those for learning foreign languages. Some of these foreign language learning systems, e.g. the Pimsleur system, use modern methods in which the student infers the grammar.
Repeatedly solving simple tactics problems is partly a memory task. Although the exact position is unlikely to appear in one of your games, the same configuration of active pieces could, and is reasonably likely to do so provided that the problem is well chosen. This situation is analogous to that in learning a foreign language. A foreign language course does not just teach you to speak and understand the phrases in the language course, but also to speak and understand any phrase that can be constructed using the same words and underlying grammar (which the student usually has to work out for himself nowadays). In both learning chess tactics and learning a foreign language, we are trying to learn a skill (create a mental program) rather than just memorise data items. The underlying biological processes are the same for both memory and learning a skill: creating neural connections. There are, however, important differences between learning a foreign language and learning chess tactics as we shall see in the next section.
Another important cognitive psychology finding is that of the superiority of active learning over passive learning. For example, the example above, actively recalling the answer “Copenhagen” is more effective than just reading the answer. In chess, finding the solution to a chess problem is more effective at building memory and skill than just reading the solution. Similarly, when studying a game, laying a sheet of paper over the book and guessing the next move is more effective than just playing the game through.
Further information on the relevant findings of cognitive psychology can be found in the following article (and its references):
This reference is particularly interesting: