Sensory memory is the brief physiological storage of information that comes from one of the five senses. It processes external stimuli automatically and does not require conscious effort.
Sensory memory is sometimes referred to as the sensory register or sensory store.
It can include the memorization of inputs from touch, taste, hearing, sight, and smell.
Sensory Memory Definition and Overview
Sensory memory is defined as:
“A type of ‘neural’ memory that holds different sensory modalities of information automatically for approximately two seconds because of neural impulses still being relayed to the brain.” (Nicholas, 2008)
Each sensory modality has a sensory register. This is the first step in perception, but only lasts for a very brief period of time, depending on the specific sensory store.
For example, visual information will only be stored in the iconic sensory store for approximately 250 milliseconds. However, auditory information can be stored in the echoic sensory store for several seconds.
Sensory memory is not controlled by higher-order cognitive processes, for example by affecting its capacity or duration.
It is also not possible for an individual to control what information is stored in sensory memory.
However, attentional control can specify which aspects of sensory information is processed further.
Types of Sensory Memory
There are five types of sensory memory, one for each sensory modality.
1. Iconic memory
The iconic sensory store processes visual images. It has a large amount of storage but limited duration, lasting for less than a second as stated above.
The brighter the visual image, the longer the duration of staying in iconic memory.
2. Echoic memory
This memory store processes auditory information. Whatever a person hears is processed in the echoic sensory store.
The duration of echoic memory lasts for several seconds. This is why it is possible to repeat what someone has said to you, even though you were not being attentive when they first said.
As a person asks for someone to repeat what they said, they might actually hear it in their mind, sort of like rewinding a recording and playing it again.
3. Haptic memory
The sense of touch is initially processed through the haptic sensory store. It includes sensations such as pressure, pain, itching, or the processing of textures such smooth or rough.
Haptic sensory nerves are located all over the body.
4. Olfactory memory
This memory store processes odors. Once odor molecules enter the nasal cavity, a chain of neurophysiological events occur which processes the odor.
Olfactory sensory memory is also linked with long-term memory. Experiences and semantic information can be associated with olfactory stimuli and improve long-term retention and recall.
Olfactory sensory memory also plays a crucial role in the perception of taste. Molecules from chewed food substances enter the nasal cavity and are involved in the perceptual process.
5. Gustatory memory
This sensory store is associated with taste and linked to the olfactory store as stated above.
It primarily involves taste receptors on the tongue that are impacted by food molecules and activate various physiological sensations that are associated with the five basic flavors: salty, sweet, bitter, sour, and umami.
Sensory Memory Examples
- Fourth of July Sparklers (Visual): If you light a sparkler and look at it for a few seconds, then close your eyes, you can see an afterimage. The afterimage is a function of bright visual stimuli lasting longer in sensory memory.
- The Coffee Connoisseur (Gustatory): Some people just seem to be born with the taste receptors of a gustatory sensory store that are naturally fine-tuned to particular coffee profiles (the expensive ones).
- Learning a Tonal Language (Echoic): Having a sensitive echoic sensory memory may facilitate learning how to speak a foreign language, especially if it is a tonal language.
- Touch Tablets for Babies (Haptic): One particular Montessori toy is designed to exercise haptic sensory memory and perception of surface roughness. It contains different sandpaper gradients and looks like this.
- The Phi Phenomenon (Iconic)) Discovered by Max Wertheimer in 1912, when lights in close proximity to each other are blinked on and off sequentially, it creates an optical illusion of movement that is often utilized in road signs directing traffic. Although it utilizes iconic sensory memory, it is actually a perception-based phenomenon.
- Asking Someone to Repeat What They Said (Echoic): Sometimes when not paying attention to someone talking, we might ask them to “say that again.” But right as we do, our echoic sensory store automatically rewinds and replays what they said. We can actually hear it, like a recording.
- Pressure Cylinders (Haptic): This Montessori toy is specially designed to build a child’s sense of pressure by exercising their haptic sensory register and related perceptual processes.
- Olfactory Sensory Memory and Semantic Recall (Olfactory): Studying in a room with an essential oils diffuser can improve recall of encoded information when smelling the same aroma as when we studied.
- Cartoon Animation (Iconic): Cartoons used to be made by drawing thousands of pictures on paper and then rapidly showing them sequentially, thus creating the illusion of movement. The history of animation starts in 1832. Although the iconic sensory store is certainly involved, the illusion is a perceptual one based on how the images are processed in the cerebral cortex.
- Great Chefs (Gustatory): A great chef not only has an incredibly sensitive gustatory sensory memory, but their olfactory sensory store is also especially receptive.
Four Fundamental Characteristics of Sensory Memory
Although each type of sensory memory is different in terms of duration and capacity, there are some common features.
- Outside of Conscious Control: The formation of a sensory memory trace is outside of conscious control.
- Specific to Sensory Modality: Information stored in sensory memory is specific to the sensory modality. For example, auditory information is only stored in echoic memory, not any of the other sensory stores.
- Depth of Storage: Each sensory memory store can hold a large amount of detailed information. For instance, the iconic sensory store, although short-lived, holds a great deal of visual stimuli in incredible detail.
- Limited Duration: Each sensory store has very limited duration. The sensory memory trace decays rapidly, and once gone, it cannot be recreated through higher-order cognitive processes.
Research Case Study: The Sperling Paradigm
George Sperling (1960) is credited with identifying the limited duration of the iconic sensory register (lasting approximately 1/3rd second).
In one study, participants were asked to recall as many letters as possible. Most participants could recall 3-4 letters, but then the image faded from their iconic sensory store.
“The fact that observers commonly assert that they can see more than they can report suggests that memory sets a limit on a process that is otherwise rich in available information” (p. 26).
In other studies, Sperling presented a tone 1/3rd of a second or longer after the stimulus card disappeared.
Sperling instructed the participants to recall letters on the top, middle, or bottom rows, depending on the tone they heard. As long as the tone was presented within 1/3rd of a second, participants could name the letters on any row.
However, the longer the delay in the tone, the greater the decline in recall. These findings suggest “Short-term information storage has been tentatively identified with the persistence of sensation…that of a rapidly fading visual image of the stimulus” (p. 26).
Applications of Sensory Memory
1. In Driving and Autonomous Vehicles (AVs)
Research has indicated that 85%–95% of the sensory cues in driving are visual (Malfetti & Winter, 1986).
This is of particular concern when considering older populations because of age-related changes in sensory functions, especially visual and auditory (see Yang & Coughlin, 2014).
The accumulated knowledge in iconic sensory memory and related perceptual processes of humans has been fundamental to the development of autonomous driving vehicles. Image sensors are designed to process visual images in the driving environment that is derived from research studying similar systems in human beings (Ignatious & Khan, 2022).
Research on the haptic sensory memory has also been explored as an information input mechanism to improve driver safety in AVs. For instance, Chiossi et al. (2022) suggest using “on-body tactile displays” can improve situational awareness.
Borojeni et al. (2017) suggest incorporating vibro-tactile stimulation to steering wheels to indicate the need for the driver to resume control of the vehicle. Kern et al. (2009) showed that tactile feedback can improve driving performance, while Enriquez et al. (2001) demonstrated that tactile feedback can decrease reaction times in identifying problems.
2. In Aviation
Pilots and air traffic controllers are required to process vast amounts of visual stimuli.
For example, the cockpit of an airplane displays an incredible amount of visual stimuli. Pilots must process that visual stimuli accurately and efficiently, particularly during take-off and landing procedures, which are the most dangerous points in flying.
Much of our understanding of factors that affect sensory encoding of visual stimuli and subsequent perceptual processes comes from the work of Christopher Wickens.
Wickens, et al. (1986) utilized the Sternberg paradigm as a way to assess pilot workload. Wickens et al. (1988) found that stress can affect performance in scenarios that require the processing of spatial working memory, but not knowledge stored in long-term memory.
As Martins (2016, p. 67) explains, the Multiple Resources Theory developed by Wickens “is one of the most influential theories to address…” issues in high workload dual-task situations.
See Wickens (2008) for more detailed information regarding human factor design considerations in task or system configuration.
There are five types of sensory memory, each corresponding to the five senses. Although each one operates according to specific parameters, there are some commonalities in terms of limited duration and capacity.
At a fundamental level, each sensory memory store is our way of detecting the environment and allowing us to navigate our surroundings.
Even though it is possible to isolate a discussion on each specific store, it is important to keep in mind that each one is connected to a complex perceptual process located in various regions of the cerebral cortex.
Knowledge regarding the iconic sensory memory has been fundamental to the development of computer-based image processing systems found in AVs, in addition to understanding the enormity of processing cockpit stimuli.
Haptic sensory memory has been investigated as a tool for improving driver safety in AVs by providing another mechanism for informing the driver of dangers or the need to take control of the vehicle.
Chiossi, F., Villa, S., Hauser, M., Welsch, R., & Chuang, L. (2022, June). Design of on-body tactile displays to enhance situation awareness in automated vehicles. In 2022 IEEE 9th International Conference on Computational Intelligence and Virtual Environments for Measurement Systems and Applications (CIVEMSA) (pp. 1-6). IEEE.
Borojeni, S. S., Wallbaum, T., Heuten, W., & Boll, S. (2017, September). Comparing shape-changing and vibro-tactile steering wheels for take-over requests in highly automated driving. In Proceedings of the 9th International Conference on Automotive user Interfaces and Interactive Vehicular Applications (pp. 221-225).
Enriquez, M., Afonin, O., Yager, B., & Maclean, K. (2001, November). A pneumatic tactile alerting system for the driving environment. In Proceedings of the 2001 Workshop on Perceptive user Interfaces (pp. 1-7).
Ignatious, H. A., & Khan, M. (2022). An overview of sensors in Autonomous Vehicles. Procedia Computer Science, 198, 736-741.
Kern, D., Marshall, P., Hornecker, E., Rogers, Y., & Schmidt, A. (2009, May). Enhancing Navigation Information with Tactile Output Embedded into the Steering Wheel. In Pervasive (Vol. 9, No. 7, pp. 42-58).
Malfetti, J. L. and Winter, D. J. (1986). Drivers 55 plus: Test your own performance. AAA Foundation for Traffic Safety, Washington, DC.
Martins, A. P. (2016). A review of important cognitive concepts in aviation. Aviation, 20(2), 65-84.
Nicholas, L. (2008). Introduction to Psychology. Cape Town: UCT Press.
Sperling, G. (1960). The information available in brief visual presentations. Psychological monographs: General and applied, 74(11), 1.
Wickens, C. D., Hyman, F., Dellinger, J., Taylor, H., & Meador, M. (1986). The Sternberg memory search task as an index of pilot workload. Ergonomics, 29(11), 1371-1383.
Wickens, C. D. (1980). The structure of attentional resources, in R. Nickerson (Ed.). Attention and performance VIII. (pp. 239–257). Hillsdale, NJ: Erlbaum.
Wickens, C. D. 2008. Multiple resources and mental workload. Human Factors 50(3): 449–455.
Winkler, I., & Cowan, N. (2005). From sensory to long-term memory: evidence from auditory memory reactivation studies. Experimental Psychology, 52(1), 3-20.
Yang, J., & Coughlin, J. F. (2014). In-vehicle technology for self-driving cars: Advantages and challenges for aging drivers. International Journal of Automotive Technology, 15, 333-340.
Dr. Chris Drew is the founder of the Helpful Professor. He holds a PhD in education and has published over 20 articles in scholarly journals. He is the former editor of the Journal of Learning Development in Higher Education. [Image Descriptor: Photo of Chris]