Why we forget

The 7 causes of memory failure

The importance of forgetting

At this point in the unit, you know the three types, processes, and stages of memory. Now, let’s move on to an equally important topic: forgetting.

“Forgetting is as important as remembering. If we remembered everything, we should be as ill off as if we remembered nothing. It would take as long for us to recall a space of time as it took the original time to elapse, and we should never get ahead with our thinking.” –William James

The dynamics of forgetting

Forgetting can occur at any memory stage

As we process information, we filter, alter, or lose much of it

Reason #1: Encoding failure

Information never enters long-term memory; not paying attention to details produces encoding failure (bigger problem as you get older)

Externalevents

Sensorymemory

Short-term

memory

Long-term

memory

Attention

Encoding

Encoding

Encodingfailure leadsto forgetting

Remember the penny activity?

Which penny is the real thing? Do you know now? Probably not.

Reason #2: Storage decay

Physical fading away of a memory trace over time when it is not used: “use it or lose it”

12345 10 15 20 25 30

10

20

30

40

50

60

0

Time in days since learning list

Percentage oflist retainedwhen relearning

Reason #3: Retrieval failure

Forgetting can result from failure to retrieve information from long-term memory

Externalevents

Attention

Encoding

Encoding

Retrieval failureleads to forgetting

Retrieval

Sensorymemory

Short-termmemory

Long-termmemory

Reason #4: Interference

Learning some items may disrupt retrieval of other information

Proactive interference:

Retroactive interference:

The two directions of interference

Limiting retroactive interference: a tip

The hour before bed is a good time to memorize new material!

Without interferingevents, recall isbetterAfter sleep

After remaining awake

1 2 3 4 5 6 7 8Hours elapsed after learning syllables

90%

80

70

60

50

40

30

20

10

0

Percentageof syllables

recalled

Reason #5: Motivations for Forgetting

Motivated Forgetting

Repression

Reason #6: Memory Construction

Memories are not files retrieved from a hard drive; they are actively and imperfectly constructed every time you retrieve them from a vast network of associations

We filter information and fill in missing pieces, often leading to distortions;

Retrieval of memories is subject to bias and suggestibility; imagination inflation

Misinformation Effect

Source Amnesia

Reason #7: Memory Disorders

Age-associated memory impairment:

Prospagnosia:

Post-concussion syndrome:

Alzheimer’s Disease: degenerative condition of the brain; affects 4 million Americans today

Other strange stories related to #6 and #7 to come…