Iconic Memory vs. Echoic Memory: Understanding Sensory Memory
Sensory memory is a brief collection of information from your senses. This includes your hearing, touch, smell, taste and vision. Sensory memory allows individuals to retain impressions of sensory information for a brief time after the original stimulus has ceased.
Your sensory memory gathers information at the highest resolution - it’s taking a quick, detailed picture of your environment. Then, it sends that information to your short-term memory. You can’t regulate how long these memories last, but they usually only stay for a couple of seconds. This helps you better understand small nuances about your environment.
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. Information first attains meaning in short-term memory, also known as working memory. This is where the conscious processing of information occurs.
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. The process that transfers information from sensory memory to short-term memory is known as attention.
Sensory memory is an automatic response considered to be outside of cognitive control. 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.
There are many different parts of your brain involved in sensory memory. Each sense follows a pathway. Memories are not stored as exact replicas of experiences; instead, they are modified and reconstructed during retrieval and recall. Memory storage is achieved through the process of encoding, through either short- or long-term memory.
It has been well documented that dual-task performance is more accurate when each task is based on a different sensory modality. It is also well documented that the memory for each sense has unequal durations, particularly visual (iconic) and auditory (echoic) sensory memory. Let's delve deeper into iconic and echoic memory.
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
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
Iconic Memory
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 memory refers to briefly retaining visual information, lasting about 100-200 milliseconds.
A recent study examined the hypothesis that iconic memory comprises fine-grained and coarse-grained memory traces (Cappiello & Zhang, 2016).
Echoic Memory
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. On the other hand, echoic memory relates to auditory information, maintaining sounds for a slightly longer duration, approximately 3-4 seconds.
It enables us to combine a series of touch sensations and to play a role in identifying objects we can’t see. fMRI studies suggest that certain neurons within the prefrontal cortex engage in motor preparation and sensory memory.
Duration of Sensory Memory
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.
Here is a table summarizing the duration of different types of sensory memory:
| Type of Sensory Memory | Duration |
|---|---|
| Iconic (Visual) | 100-200 milliseconds |
| Echoic (Auditory) | 3-4 seconds |
| Haptic (Touch) | Brief, less defined |
| Olfactory (Smell) | Brief, less defined |
| Gustatory (Taste) | Brief, less defined |
How Sensory Memory Works
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.