2.7 Forgetting and Other Memory Challenges

In the 1880s, Hermann Ebbinghaus memorized lists of nonsense syllables (like 'DAX' and 'QEB') and tested himself after different delays. He found that most forgetting happens quickly, within the first hours or day, and then the rate of forgetting slows and levels off. Graphed with time on the x-axis and percent retained on the y-axis, the forgetting curve drops steeply at first and then flattens.

This is why reviewing soon after learning, and then again at spaced intervals, is so effective: each review catches the memory before most of it fades.

To keep interference straight: proactive works forward (old disrupts new), and retroactive works backward (new disrupts old).

• Encoding failure: the information never got into long-term memory. Most people can't draw the exact design of a coin they've handled thousands of times because they never paid attention to the details.
• Proactive interference: old learning interferes with new learning. Your old locker combination keeps popping up when you try to remember the new one.
• Retroactive interference: new learning interferes with old learning. After learning Spanish, you have trouble recalling the French you studied years ago.
• Retrieval failure: the memory is stored, but you can't access it without the right cue. The tip-of-the-tongue phenomenon, when you're sure you know a word and may even know its first letter but can't produce it, is a classic example.
• Repression: psychodynamic theorists believe painful memories can be pushed out of conscious awareness to protect the self from anxiety. Many researchers doubt this happens, since traumatic experiences are often remembered all too well.

Memory isn't a video recording. Each time you recall something, you rebuild it from stored pieces, your general knowledge and your expectations, and then store it again. This is called constructive (or reconstructive) memory, and it means memories can change each time they're recalled and stored again.

The misinformation effect happens when misleading information after an event changes your memory of it. In Elizabeth Loftus's classic studies, people watched a video of a car crash. Those asked how fast the cars were going when they 'smashed' into each other estimated higher speeds than those asked about cars that 'hit' each other, and a week later, more of the 'smashed' group falsely remembered seeing broken glass.

Source amnesia (source misattribution) is remembering information but forgetting where it came from. You might be sure you saw something happen when you actually heard about it from a friend or saw it in a movie.

Imagination inflation is when repeatedly imagining an event makes you more confident it really happened. Together, these effects explain why eyewitness confidence isn't a reliable sign of accuracy, and why careful, non-leading questioning matters in police interviews and therapy.