Iconic and Echoic Memory: Definitions and Functions
Sensory memory in psychology refers to the short-term retention of sensory information, like sights, sounds, and smells, immediately following stimuli input. Sensory memory is a very short-term memory store for information being processed by the sense organs. It allows individuals to retain impressions of sensory information for a brief time after the original stimulus has ceased.
Sensory memory allows individuals to remember great sensory detail about a complex stimulus immediately following its presentation. Sensory memory is an automatic response considered to be outside of cognitive control. Information from sensory memory has the shortest retention time, ranging from mere milliseconds to five seconds. It is retained just long enough for it to be transferred to short-term (working) memory.
Sensory memory functions in the following way:
- You experience a sense.
- The area of your brain responsible for that sense (sensory cortex) briefly activates. It happens very quickly, like pressing a button.
- You focus your attention on only the important pieces of information gathered.
- You move those pieces to your short-term memory.
Unlike sensory memory, which merely stores raw sensory input, short-term memory interprets and assigns meaning to these stimuli, allowing us to understand and respond to our environment. Information first attains meaning in short-term memory, also known as working memory. This is where the conscious processing of information occurs.
There are many different parts of your brain involved in sensory memory. Each sense follows a pathway. Let’s say you hear a sound. This sound converts into an electrical signal that nerve fibers carry into your brain. It first passes through your brainstem and then up through your thalamus (the middle of your brain). Your thalamus directs the signal to the correct area specific to the sense.
Your sensory memory only holds information for about 0.2 to 2 seconds. This can vary based on which sense you experience. For example, iconic memory (vision) typically lasts for 1 second.
Sensory memory has a large capacity. This is because you often use multiple senses at the same time. For example, you may use all five senses when you’re eating a meal. You see the food. You feel the texture on your tongue. You smell the different ingredients. You hear the crunch when you chew. And you taste it. Your sensory memory can take in information from all of those senses as they happen.
While sensory memory has a large capacity, it only lasts for a few seconds before either moving to another memory storage area of your brain or disappearing so you can experience other senses.
Types of Sensory Memory
Your five senses make up the types of sensory memory including:
- Echoic memory: Hearing
- Haptic memory: Touch
- Gustatory memory: Taste
- Iconic memory: Vision
- Olfactory memory: Smell
Echoic memory is a type of sensory memory that specifically pertains to auditory information (sounds). The information which we hear enters our organism as sound waves. It enables us to combine a series of touch sensations and to play a role in identifying objects we can’t see.
Iconic memory is the visual sensory memory register that stores visual images after its stimulus has ceased (Pratte, 2018). This fleeting storage of visual information allows the brain to process and understand visual stimuli from our environment.
Iconic and echoic memory are types of sensory memory, but they differ in the sensory modality they process. Iconic memory refers to briefly retaining visual information, lasting about 100-200 milliseconds. On the other hand, echoic memory relates to auditory information, maintaining sounds for a slightly longer duration, approximately 3-4 seconds.
Let's look at a table comparing iconic and echoic memory:
| Feature | Iconic Memory | Echoic Memory |
|---|---|---|
| Sensory Modality | Visual | Auditory |
| Duration | 100-200 milliseconds | 3-4 seconds |
| Function | Briefly retains visual information | Maintains sounds for processing |
It also depends on the characteristics of a sound, including: duration, frequency, intensity, volume and language (with spoken word). The term echoic stems from the word echo, which is in reference to the brief echo, or the reverberation of sound that is transmitted neurologically via this type of sensory memory.
Echoic memory occurs automatically whether a person consciously tries to remember what they've heard. Echoic memory is the brief sensory memory of audible sounds. An echoic memory example occurs with conversation.
Echoic memory allows the brain to retain spoken syllables in order for the brain to process them into intelligible speech.
Echoic memory is processed in the left hemisphere of the brain. The left hemisphere of the brain primarily processes echoic memory.
The brain processes auditory information from echoic memory in the primary auditory cortex (PAC). The PAC of the left ear stores sounds heard with the right ear and vice versa. Sounds heard with both ears are stored in bilateral PACs.
The purpose of echoic memory is to store audio information as the brain processes the sound. It also holds bits of audio information, which gives meaning to the overall sound.
When you hear something, your auditory nerve sends the sound to your brain. It does this by transmitting electrical signals. At this point, the sound is “raw” and unprocessed audio information. Echoic memory occurs when this information is received and held by the brain. Specifically, it’s stored in the primary auditory cortex (PAC), which is found in both hemispheres of the brain.
The information is held in the PAC opposite of the ear that heard the sound. For instance, if you hear a sound in your right ear, the left PAC will hold the memory. But if you hear a sound through both ears, both the left and right PAC will retain the information. After a few seconds, the echoic memory moves into your short-term memory. This is where your brain processes the information and gives meaning to the sound.
The process of echoic memory is automatic. This means audio information enters your echoic memory even if you don’t purposely try to listen. In fact, your mind is constantly forming echoic memories.
Iconic memory is sensory memory from visual input. A recent study examined the hypothesis that iconic memory comprises fine-grained and coarse-grained memory traces (Cappiello & Zhang, 2016). Close your eyes for one minute, and hold your hand about 25cm from your face ad then open and close your eyes.
Sensory memory, also called the sensory register, holds information from the senses. It can be further broken down into three types: Iconic memory, or visual sensory memory, handles visual information. Haptic memory retains information from your sense of touch. Echoic memory holds audio information from your sense of hearing.
But iconic memory is much shorter. It lasts for less than half a second. That’s because images and sounds are processed in different ways. Since most visual information doesn’t immediately disappear, you can repeatedly view an image. Plus, when you look at something, you can process all the visual images together.
Echoic memory is longer, which is useful because sound waves are time sensitive. They can’t be reviewed unless the actual sound is repeated. Also, sound is processed by individual bits of information. Each bit gives meaning to the previous bit, which then gives meaning to the sound. As a result, the brain needs more time to store audio information.
The duration of information in sensory memory varies based on the type of sensory input. Iconic (visual) memory lasts about 100-200 milliseconds, echoic (auditory) memory can last up to 3-4 seconds, while haptic (touch), olfactory (smell), and gustatory (taste) memories have less defined durations but are generally considered brief.
Echoic memory lasts three to four seconds before the information disappears. If someone wishes to remember the brief burst of information in their echoic memory, they must consciously transfer the auditory information into their short-term memory. Long-term memory allows someone to recall a melody or recognize bird songs that were heard years ago.
Olfactory sensory memory involves the brief retention of smell stimuli. Gustatory sensory memory is the temporary storage and recall of taste information.
Examples of Sensory Memory
Examples of sensory memory include:
- Echoic memory: The melody of your favorite song continuing even after the song finished playing
- Haptic memory: Continuing to feel the grasp after someone lets go of your hand
- Gustatory memory: The taste of dinner remaining after you’ve finished your meal
- Iconic memory: Seeing the color of fireworks after they’ve faded
- Olfactory memory: Continuing to smell bread after walking out of a bakery
Here are a few everyday examples of echoic memory:
- Talking to another person Spoken language is a common example. When someone talks, your echoic memory retains each individual syllable. Your brain recognizes words by connecting each syllable to the previous one. Each word is also stored in echoic memory, which allows your brain to understand a full sentence.
- Listening to music Your brain uses echoic memory when you listen to music. It briefly recalls the previous note and connects it to the next one. As a result, your brain recognizes the notes as a song. Echoic memory allows the brain to interpret individual notes into a recognizable song. Notes played on a piano are stored in echoic memory long enough for the brain to process the notes into a recognizable song or melody.
- Asking someone to repeat themselves When someone talks to you while you’re busy, you might not fully hear what they say. If they repeat what they said, it will sound familiar because your echoic memory heard them the first time. When someone is distracted and asks a friend, "What did you say?" Echoic memory is the reason that they immediately recognize the words even when they weren't actively listening to the conversation. The person's echoic memory retained the words even though it was not done consciously. Echoic memory allows the recall of words that were spoken when not listening.
This brief duration means your brain can make many echoic memories throughout the day.
A Funny Example: Think back to the last time you heard someone tell you a funny joke. After you finished laughing, you probably either repeated it out loud, or at minimum, replayed what you just heard over again in your head. Chances are that if you were asked to repeat the joke word for word immediately after you heard it, assuming it wasn't too long, you would do pretty well. So, how does auditory information, or using the example above, the variety of sound qualities emanating from the joke teller's mouth (pitch, volume, and tone) make its way to our brain when so much is going on around us in our environments? As you might have guessed, it has a lot to do with echoic memory.
When testing echoic memory, someone is given a series of spoken letters or numbers. They are less able to give a whole report and recall all of the spoken letters. If asked to recall a specific portion of the spoken letters, the partial recall is much higher and accurate. Partial reporting surpasses accuracy when compared to the whole reporting.
Afterward, Sperling ran a second, slightly different experiment using the partial report technique. The individuals managed to recall the letters if the tone was sounded within 1/3rd of a second following the display of the letters (Sperling, 1960). Sperling hypothesized that the participants had forgotten this information while attempting to recall it. In other words, Sperling held that all of the nine letters were, in fact, stored in the participants’ memory for a very short time, but that this memory had faded away.
The process that transfers information from sensory memory to short-term memory is known as attention.
fMRI studies suggest that certain neurons within the prefrontal cortex engage in motor preparation and sensory memory.
Factors Influencing Echoic Memory
All humans have echoic memory. However, various factors can influence how well someone has this type of memory. Possible factors include:
- age
- neurological disorders, such as Alzheimer’s disease
- psychiatric disorders, such as schizophrenia
- substance use
- hearing loss or impairment
- language disorders
We all forget things sometimes. It’s also normal to experience some memory loss as we get older. But if you’re having serious memory issues, it’s important to see a doctor.
Seek medical help if you have memory problems, such as:
- getting lost in familiar places
- forgetting how to say common words
- repeatedly asking questions
- taking longer to do familiar activities
- forgetting names of friends and family
Depending on your specific issues, a doctor might refer you to a specialist, like a psychologist or neurologist.
Though we all have echoic memory, factors like age and neurological disorders can affect how well you recall sounds. It’s also normal for memory to decline with age.
