Questions: Retrieval-Induced Forgetting and Output Interference

Question 1

In a retrieval practice experiment, subjects study these pairs: Fruit–Mango, Fruit–Orange, Fruit–Peach, Tool–Hammer, Tool–Wrench. They then practice retrieving Orange and Peach. On a final test, which item would retrieval-induced forgetting predict is recalled *worst*?

• A. Hammer, because it was never practiced at all
• B. Mango, because it shares a category with practiced items but was never retrieved
• C. Orange, because repeated retrieval causes trace decay through overuse
• D. Wrench, because Tool items received no retrieval practice at all

Answer: (B)

The critical finding of retrieval-induced forgetting is that *unpracticed items from practiced categories* are suppressed below the baseline recall rate of unpracticed items from unpracticed categories. Mango was never retrieved, but it is a categorical competitor to Orange and Peach — when those items were retrieved, Mango was co-activated and then inhibited to reduce interference. Hammer and Wrench were never co-activated as competitors, so they remain at the baseline level. This is what makes RIF a distinctive phenomenon: the suppression is not about practice amount but about competitive relationship to practiced items.

Question 2

A skeptic argues that retrieval-induced forgetting is simply due to differential rehearsal — practiced items get more mental repetition, so unpracticed items seem worse by comparison. What is the strongest evidence against this explanation?

• A. The effect disappears when subjects are given a second study phase before testing
• B. Unpracticed items from practiced categories are recalled worse than unpracticed items from unpracticed categories, even though both groups were studied equally often
• C. The effect only occurs when retrieval practice uses the same cues as the final test
• D. Practiced items are recalled better than unpracticed items

Answer: (B)

The differential rehearsal explanation predicts that items studied more will be recalled better — but it cannot explain *suppression below baseline*. Items from unpracticed categories (e.g., Hammer) were studied exactly as many times as the suppressed items (e.g., Mango). The only difference is that Mango shares a category with items that were retrieved. If rehearsal alone explained the pattern, both groups should perform equally on the final test. The fact that Mango is recalled *worse* than Hammer — despite identical study exposure — demonstrates that something beyond differential rehearsal is operating. That something is inhibitory suppression.

Question 3

Retrieval-induced forgetting is considered an inhibitory effect because the suppression of non-practiced items persists even when those items are tested using new, neutral cues unrelated to the original practice context.

• T. True
• F. False

Answer: True

If RIF were simply a failure of cue reinstatement — the original cue is 'used up' by practiced items — the suppression would disappear when a different cue is provided. But RIF persists even with unrelated cues on the final test. This shows that the memory trace itself has been weakened (its resting activation lowered), not just that the cue has become less effective. This persistence is key evidence for the inhibitory suppression account rather than cue-based competition accounts.

Question 4

Retrieval-induced forgetting occurs because non-practiced items from practiced categories receive less total study time than control items from unpracticed categories.

• T. True
• F. False

Answer: False

This is precisely the differential rehearsal explanation that research has ruled out. In the standard RIF paradigm, all studied items receive identical exposure during the study phase. Non-practiced items from practiced categories (e.g., Mango) and items from unpracticed categories (e.g., Hammer) were both studied equally. The suppression of Mango below Hammer's recall level cannot be attributed to less study time. It reflects active inhibition triggered by the retrieval of categorical competitors — not a passive encoding difference.

Question 5

Why is retrieval-induced forgetting considered evidence of *inhibitory suppression* rather than a simple encoding or rehearsal advantage for practiced items?

Model answer: RIF is evidenced by impaired recall of non-practiced items *below baseline* — that is, below the recall rate of items from unpracticed categories that received identical study exposure. An encoding or rehearsal advantage for practiced items would explain why Orange is recalled better than Hammer, but it cannot explain why Mango is recalled *worse* than Hammer. The only difference between Mango and Hammer is that Mango competed with retrieved items. The active suppression of competitors, not just the strengthening of practiced items, is the signature of inhibitory suppression.

The key logical move is distinguishing between 'practice helps practiced items' (uncontroversial) and 'practice hurts related non-practiced items' (the RIF claim). The evidence for the latter requires a proper baseline — unpracticed items from unpracticed categories — that controls for study exposure. When the suppressed items fall below that baseline, differential rehearsal is ruled out as an explanation, and some active inhibitory process must be invoked. This is why RIF challenges the naïve view that retrieval only strengthens memory.