The 3 Stage Processing Model of Memory

Melton (1963) discovered that there were three stages in the process of memory. These processes are encoding, storage and retrieval.

A great way to understand the 3 stage processing model of memory is to think of your brain as a computer. For computers, information is input via external devices like a webcam, keyboard or controller. For humans, the senses are the way we receive information. Through sight, hearing and touch etc.

Computers have to store information, like documents you are working on. In the same way, our brains store the encoded information coming from the environment.

Eventually, a computer will be used to output what was stored. This may look like a printout of an important document. Our brains can also output specific information we may need, this is known as retrieval.

Fig 2. Researchers have theorised different memory stored in the brain.

Memory Encoding

Encoding is the memory process that converts incoming information into a format that can be stored by the brain. It is a fundamental step in the creation of memories. Once the information has been encoded, it is then able to be retrieved from either the long-term memory or the short-term memory. There are three ways in which information is usually encoded:

• Acoustic (Sound)

• Visual (image)

• Semantic (Meaning)

Different Types of Memory

Before diving into the differences between the types of distinctions within the memory processes, you first have to be familiar with short-term memory (STM) and long-term memory (LTM). The distinction between these two will help you understand the intricacies of long-term memory.

Different types of memory - memory processes

Short-term memory is information from the environment that is paid attention to. This information is held for a short duration of about 18 seconds. The study performed by Peterson and Peterson (1959) supports the short-term memory being 18 seconds.

This was found through the discovery that when participants had to recall trigrams, the recall rate dropped drastically after 18 seconds. This suggests that they hit the duration limit of short-term memory which was around 18 seconds.

• Information in the short-term memory is coded acoustically. Think about when you have to write down a phone number. To make sure you don't mess up, you would usually repeat the numbers in your head so you don't forget. This is the same.

• Information in long-term memory is coded semantically. Long-term memory is information that was in short memory but has been rehearsed. This could be through elaborative rehearsal where the information is given additional meaning. Alternatively, it could be through maintenance rehearsal which is the information being repeated consistently.

Tulving (1972) proposed that long-term memory, unlike short-term memory was not one single store, but rather it was divided into 3 types of memory. These were:

• Episodic
• Semantic
• Procedural

Following further research, long-term memory was simplified into two distinct categories, procedural and declarative. Declarative memory was further divided.

Procedural Memory

Procedural memory is where memories of how to perform certain actions are stored.

Procedural memory does not involve conscious thought, when you ride a bike you aren't constantly trying to think of how to perform each action, you just do it. Unlike the previous types of memory, it is non-declarative as it can not be put into words easily.

Declarative Memory

Declarative memory focuses more so on the meaning behind particular events.

Declarative memory can be further divided into:

• Episodic
• Semantic

Let's take a look at each one in more detail.

Episodic Memory

Episodic memory is responsible for storing information about personal events (episodes) that have happened to you.

This type of memory requires conscious thought because you have to try and remember the event and it is declarative as you can easily explain the memory in words.

Semantic Memory

Semantic memory is responsible for storing meaning, facts and information about the world.

Semantic memory has to be consciously thought of to be accessed and like episodic memory, it is declarative because you can put the memory into words.

Fig 3. Recalling the capital of a country is a form of semantic memory.

Psychological Evidence of Memory Processes

Let's take a look at 3 pieces of psychological evidence around memory processes.

• Cohen and Squire (1980) found evidence for the distinction between declarative and procedural knowledge through amnesia patient research. Patients with amnesia usually find it extremely difficult to retain and create episodic and semantic knowledge. Episodic and semantic memories that they had before the onset of amnesia are usually lost but procedural memories seem to be unaffected. This suggests that there is a distinction between declarative and procedural memories since if there was not a distinction, both types of memories would be affected equally.
• Bahrick, Bahrick, and Wittinger (1975) wanted to investigate a concept called 'very long term memory' (VLTM). They tested almost 400 participants ranging from ages 17 to 74. The participants were asked to write down the names of those who were in their graduating class. There were multiple conditions such as a free recall test and a photo recognition test.
  • The results showed that those who were tested within 15 years of graduating were 90% accurate in recalling names and faces. The number of people who graduated within 48 years, dropped to 80% for names and 70% for faces. This study thus indicated that the duration of long-term memory was potentially unlimited. This then also clearly suggested that there was a difference between the LTM and STM as the duration of STM was only 18 seconds.