01 / 23

Forgetting & Other
Memory Challenges

Explore why we forget, how memories distort over time, and the key theories that explain failures in encoding, storage, and retrieval.

AP Psychology

What Is Forgetting?

Forgetting is the inability to retrieve previously stored information. It is not always a failure: sometimes forgetting serves an adaptive purpose, clearing irrelevant data so we can focus on what matters most.

The Ebbinghaus Forgetting Curve

0% 50% 100% 0 1 day 3 days 6 days 31 days Time Elapsed Retention % No review Spaced review

Three Reasons We Forget

Encoding Failure
Information never entered long-term memory in the first place: you can't retrieve what was never stored.
Storage Decay
Memory traces physically fade over time if not rehearsed or reactivated, following the Ebbinghaus curve.
Retrieval Failure
The memory exists but the right cue is missing: like a book in a library with no catalogue entry.

Encoding Failure in Detail

Sensory Input Attention Gate Long-Term Memory Never encoded

If you never paid attention to the information, it was never deeply processed. Classic example: you cannot recall the details of a penny despite seeing thousands, because you never encoded those features.

Interference Theory

Sometimes forgetting happens not because a memory fades, but because other memories compete with it. There are two main types of interference:

Proactive Interference
Old information interferes with learning new information. Example: your old phone number makes it hard to remember your new one.
Retroactive Interference
New information interferes with recalling old information. Example: learning Spanish vocabulary disrupts your ability to recall French vocabulary.

Visualizing Interference

Proactive Old Info New Info ✕ Blocks new learning Retroactive Old Info New Info ✕ Disrupts old recall Learn A Learn B Test Proactive: A blocks B recall Retroactive: B blocks A recall

Proactive vs Retroactive

Proactive Retroactive
Direction Old → blocks New New → disrupts Old
Example Old password interferes with new New password makes you forget old
What is tested? Recall of the new material Recall of the old material
Root meaning "Pro" = forward "Retro" = backward

Retrieval Cues & Motivated Forgetting

1
Retrieval cues are stimuli that help activate a memory trace: a smell, a place, or a word can unlock a stored memory.
2
Tip-of-the-tongue (TOT) phenomenon: you know a word exists but cannot quite retrieve it, suggesting partial activation of the memory.
3
Motivated forgetting (repression): Freud proposed that we unconsciously push threatening memories out of awareness as a defense mechanism.

Context & State Dependent Memory

Context-Dependent
Recall improves when the physical environment at retrieval matches the environment at encoding. Studying in the same room you will be tested in helps.
State-Dependent
Recall improves when your internal state (mood, arousal, sobriety) at retrieval matches the state at encoding.

The Misinformation Effect

Elizabeth Loftus demonstrated that misleading post-event information can alter a person's memory of an original event. In her classic study, participants who heard "How fast were the cars going when they smashed into each other?" gave higher speed estimates than those who heard "hit."

Original Event Misleading Question Distorted Memory Cars collide "smashed" vs "hit" Higher speed estimate

Source Amnesia & False Memories

1
Source amnesia (source misattribution): remembering the information but forgetting where or how you learned it.
2
False memories: constructed memories of events that never happened, often feeling as vivid and real as true memories.
3
Imagination inflation: repeatedly imagining an event increases confidence that it actually occurred.

How to Identify the Type of Forgetting

1
Was the information ever encoded? If the person never paid attention, it is an encoding failure.
2
Did time alone cause the loss? If the memory simply faded without competing information, it is storage decay.
3
Is another memory competing? If old blocks new, it is proactive interference. If new disrupts old, it is retroactive interference.
4
Is the cue missing? If the memory returns with the right prompt, it is a retrieval failure.
5
Was the memory altered? If post-event information changed it, consider the misinformation effect or source amnesia.

Example: The New Phone Number

Maria just changed her phone number. When someone asks for it, she accidentally gives her old number instead. What type of forgetting is this?

Example: The Scuba Diver Study

Godden and Baddeley (1975) had divers learn word lists either underwater or on land. Recall was best when the test environment matched the study environment.

Study: Land Test: Land = Best recall Study: Water Test: Water = Best recall Study: Land Test: Water = Worse recall

Example: Leading Questions in Court

A witness sees a car accident at an intersection with a yield sign. During questioning, the attorney asks, "Did you see the car run the stop sign?" Later, the witness recalls a stop sign instead of a yield sign.

Common Mistakes

✕ Mixing Up Interference Types
Remember: proactive = old blocks new ("pro" = forward). Retroactive = new disrupts old ("retro" = backward).
✕ Confusing Decay with Interference
Decay is about time passing. Interference is about competing memories. They are distinct theories of forgetting.
✕ Treating Repression as Proven
Freud's repression theory is not strongly supported by modern research. AP exams expect you to note its controversial status.

Summary of Memory Challenges

Concept Definition Key Detail
Encoding Failure Never stored Lack of attention
Storage Decay Fades over time Ebbinghaus curve
Proactive Interference Old blocks new "Pro" = forward
Retroactive Interference New disrupts old "Retro" = backward
Retrieval Failure Missing cue TOT phenomenon
Misinformation Effect Post-event distortion Loftus research
Source Amnesia Forget the origin Linked to deja vu

Question 1 of 5

After learning Italian for two years, Kenji begins studying Portuguese. He finds that his Italian vocabulary keeps intruding when he tries to speak Portuguese. This is an example of:

Question 2 of 5

A witness to a robbery is later told by a friend that the robber had a beard. At trial, the witness confidently recalls the robber having a beard, even though security footage shows no beard. This best illustrates:

Question 3 of 5

You studied for your psychology exam in the school library. According to the encoding specificity principle, your recall would likely be best if you:

Question 4 of 5

You know you have seen the actor in another movie, and the answer feels like it is right on the edge of your awareness, but you cannot quite produce the name. This is known as:

Question 5 of 5

According to Ebbinghaus's forgetting curve, which of the following is true about the rate of forgetting?