I’m enamored with the idea of inhibition as an agent. I like that it sounds ironic yet is consistent with every example I can conjure of compensatory systems. Theories of the role of dark matter and dark energy in the movement of the universe, for example. In the brain, the inhibitory function of the neurotransmitter GABA regulates neural information exchange, and some photoreceptors' inhibitory response to light allows the perception of edges or contrast. The overall action of inhibition, in the body at least, seems to be to moderate. Without inhibitory forces, we would be tempests of action without regulation; we wouldn’t have coordinated movement or know the difference between a thought and something that occurred outside of the mind.

Inhibitory forces are yin agents: operating in concert with and yet diametrically to and often unobservable in contrast with the obvious yang action. When we don't fail to account for them altogether, we need to devise oblique means with which to measure them.

For example, there are a number of paradigms for measuring the effect of cognitive inhibition on the recall of items stored in memory. One of these, the Retrieval-Induced Forgetting, or RIF, paradigm, usually involves a number of word completion tasks that pair like words: a category and a member of that category, such as FRUIT: AP____ Some subset of items from one of the categories is rehearsed and later all items from all categories are recalled, regardless of rehearsal status.

Using this paradigm, the impact of rehearsal on the ability to recall all items in a given category is considered, so I’ve heard, a striking, counterintuitive finding. I’m a little familiar with cognitive tasks of this kind, so when I first read about this paradigm, it seemed easy to guess what would happen if the task has worked as it should.

I wonder what you would think? There are no comments here and I’m not about to wait for mail before posting the answer. But it would be interesting to know what people intuitively think would happen to your ability to recall all items if you rehearsed some items of a category, such as APPLE, ORANGE, BANANA, but not PINEAPPLE, GRAPE, APRICOT, and then didn’t rehearse any items from another category such as METAL.

Guesses?

Well, as it turns out, and as you might expect, recall for rehearsed items (APPLE, ORANGE, BANANA) is better than for unrehearsed items from any other category. The surprising part is that the unrehearsed items from the same category as the rehearsed items are recalled more poorly than any other items overall. That is, you would remember APPLE, ORANGE, and BANANA best, then IRON, SILVER, GOLD the next best. You would do worse at recalling PINEAPPLE, GRAPE, and APRICOT. This is the RIF effect and it demonstrates the effect of cognitive inhibition as a memory aid. That is, inhibition as the agent that helps you remember what seems more important to remember.

I love how the specific theories we design to isolate one mechanism of functioning together reinforce the consistent behavior of the universe. THAT probably is intuitive, and yet I don’t hear a lot of people talking about it. It wouldn’t make sense that thought or memory might have radically different mechanisms than those of neurons; or that neurons in the amygdala would behave differently than photoreceptors in the eye. Or that these vast organisms could operate independently of the rules of the particles that comprise them. But too often our focus is (justifiably) local and I relish the moments when I can draw these broader associations.

Practical implications of the RIF effect? Think if you’re studying for an exam. If you focus on a subset of the material you may compromise your ability to recall unstudied material. You might be better off studying all of the material equally or not studying at all.