Forgetting in Psychology

Define Forgetting in Psychology

According to the American Psychological Society, forgetting in psychology refers to the inability to remember something previously learned.

Forgetting is indeed expected in all humans, but certain types of forgetting are not. These are called pathological forgetting, which refers to the forgetting that can be described in diagnostic terms.

Causes of Forgetting in Psychology

Why do we forget things? It seems like a simple question, but psychologists have invested decades of research in answering it. Two main factors are considered to cause forgetting: brain damage and interference.

Forgetting in Psychology: Brain Damage

Henry Molaison (HM) was a patient who got a lobotomy of his brain performed to cure epilepsy he suffered from. As part of the lobotomy, his hippocampus and amygdala were removed. The surgery successfully prevented HM from later suffering epilepsy symptoms. However, after surgery, HM was not able to form new memories.

Scoville and Milner (1957) conducted a study to test brain surgery's effects on HM's memory. Researchers detected severe anterograde amnesia in HM. The study concluded that damage to the hippocampus structure is related to anterograde amnesia.

Forgetting in Psychology: Interference

The second cause for forgetting that psychologists have described is interference. This refers to the forgetting that happens when memories disturb one another.

In 2009, Ellenbogen and other researchers designed a study to test whether learning a list of works would affect learning another list of words.

Participants were asked to learn a list of words called the A-B list. Participants were tested on their recalling of the list 12 hours later. After the test, participants were asked to learn another list of words called A-C. The A-C list's first word was the same as the first one in the A-B list. Every other word, however, was different.

Even if participants only invested 10 minutes learning the A-C list, their scores dropped significantly when they were tested on the A-B list again. This was taken as evidence that new learning interferes with previous learning.

These findings lead to the development of a theory of forgetting. Let's take a look at it.

Theories of Forgetting in Psychology

Forgetting is the loss of information from the long-term memory store. Several theories have been proposed to explain why these occur.

Forgetting in Psychology: Interference Theory

The interference theory of forgetting in psychology explains the causes of forgetting in long-term memory (LTM).

The theory suggests that when information is being processed to be memorised, it can be mixed with other information, resulting in memory distortion and disruption. Interference is more likely to happen if the memories are similar.

Time of learning also affects the likelihood of inference. Interference is less likely to occur when there is a large gap between learning instances. Furthermore, the theory described two different types of interference in forgetting.

Forgetting in Psychology: Trace Decay Theory

The trace decay theory explains forgetting in short-term memory.

Short-term memory can only keep information for a given period (usually between 15 and 30 seconds). If such information is not rehearsed, then such information decays and is no longer able to be remembered.

Evidence of the trace decay theory comes from a laboratory experiment conducted by Peterson and Peterson in 1959. In this study, participants had to learn trigrams one at a time in intervals of 3, 6, 9, 12, 15 and 18 seconds.

After learning each trigram, participants were asked to count a number backward in threes or fours until a light appeared on the screen. After the presentation of the light, the participant would recall the trigram. This was included to prevent rehearsal.

The results indicated that the shorter the interval between learning and recalling was, the better the performance. After 3 seconds, around 80% of the trigrams were recalled, while after 18 seconds, only 10% were recalled.

Fig. 1. Forgetting is when an individual can no longer retrieve information that the memory stores previously encoded.

Types of Forgetting in Psychology

There are different types of forgetting. These types emerge based on the other causes of such memory loss. When forgetting occurs due to interference, the forgetting can either be proactive or retroactive.

Forgetting in Psychology: Proactive Interference

Proactive interference (PI), in simple words, reflects that what we have already known previously interferes with information we recently learned, leading to forgetting new memory.

Forgetting in Psychology: Retroactive Interference

Retroactive interference (RI), differently, reflects the forgetting that takes place when the new information interferes with the old one.

The information we recently learned interferes with what we already know, which leads to forgetting old memory.

Memory loss is called amnesia, when forgetting occurs due to brain damage. Amnesia can either be anterograde or retrograde.

Forgetting in Psychology: Anterograde Amnesia

Anterograde amnesia is memory loss that affects an individual's ability to create memories after brain surgery. However, the memories created before the brain surgery remain intact.

Forgetting in Psychology: Retrograde Amnesia

Anterograde amnesia is memory loss that affects an individual's ability to create memories before brain surgery. The individual, however, can learn new things and skills after such brain surgery.

Factors Affecting Forgetting

Psychologists have identified factors that affect forgetting. These factors are context and state. In this way, there exist context-dependent memories and state dependent-memories.

Forgetting in Psychology: Context-Dependent Memories

Maybe it has happened to you that you turn into the pantry and ask yourself: what was I getting from here? You forgot why you went there or what you were getting. This is an example of how context can affect forgetting.

According to the context theory of forgetting, memories can be context-dependent. And changing such context can induce forgetting.

Tulving (1974) stated that when humans learn information, they also learn details about the environment in which the learning took place.

Putting this idea under investigation, Godden and Baddeley (1975) designed a study with divers to test whether people would remember better if the information was tested in the same context where it was learned. To do this, they asked a group of divers to memorise a list of words underwater or on a beach.

The participants were split into four groups:

1. Learn words underwater and recall words underwater
2. Learn words underwater and remember words on the beach
3. Learn words on the beach and remember words on the beach
4. Learn words on the beach and remember words underwater

It was found that the participants were able to recall the words more accurately when they learned the terms, and the place they recalled the words was the same. And they were significantly less accurate when the two contexts didn't match.

Fig. 2. Godden and Baddeley (1975) recruited divers in their study.

Forgetting in Psychology: State-Dependent Memories

These are memories that are triggered by a specific state or mood that a person is in. For example, you may be reminded of your dog passing away when you are experiencing a sad moment, compared to when you are happy.

Goodwin and colleagues studied this in 1975. They conducted a study that tested whether participants' states affected their forgetting of words. To test the state dependency, they used alcohol. Participants were asked to learn a list of words one day and were tested the day after. Four experimental groups emerged:

Group 1: Participants were sober on the day of the learning and the day of the recalling.

Group 2: Participants consumed alcohol during learning and recall days.

Group 3: Participants consumed alcohol on the learning day and were sober on the recalling day.

Group 4: Participants were sober on the learning day and consumed alcohol on the recalling day.

The results indicated that individuals in groups 1 and 2 performed better than those in groups 3 and 4. The best performance, however, was the one from individuals in group 1. These results can be interpreted as evidence favouring state dependency on memories.