Imagine that you’re at the movies, having just watched a new blockbuster hit. As you make your way towards the exit, the smell of buttery popcorn wafts into your nose. Suddenly, it’s all you’re focusing on—you look over to the concession stand and watch the kernels spill over into the popcorn machine. For a fleeting second, all you are thinking of is the smell of popcorn. Even as you step outside the theatre, a faint smell of popcorn seems to remain in your brain. You’d be able to describe it perfectly to someone.

It is thanks to our sensory memory that we are able to collect information from our senses and briefly retain it. Your sensory memory picked up on the smell of popcorn, even in an environment with multiple, diverse stimuli, and allowed you to hold onto that impression as you left the theatre. 

Each of our five senses has a different kind of sensory memory, and depending on the sense, the memory can last anywhere from a quarter of a second to four seconds. Although our sensory memory is extremely short-term, it is what allows us to register the vast amount of information that we encounter in our daily environments. It is an automatic process that causes us to pay attention to specific stimuli within the environment to be able to transfer important information into our short-term memory.¹ 

Echoic Memory: A type of sensory memory related to auditory information. You can remember a sound, somewhat like an echo, even if you weren’t paying attention to it, for about two to four seconds. For example, if you are not paying attention in class but hear the teacher call your name, you can usually access the question they just posed thanks to echoic memory.¹ 

Haptic Memory: A type of sensory memory related to tactile information that lasts around two seconds. For example, you may still be able to feel vibrations on your body after getting up from a massage chair.¹  

Gustatory Memory: A type of sensory memory related to taste information, which lasts for only a second or two. For example, after you take a sip of wine, the taste will linger in your mouth briefly.¹ 

Iconic Memory: A type of sensory memory related to visual information, which only lasts for around a quarter or half of a second. For example, after turning off a flashlight, you may still see light for a fraction of a second.¹

Olfactory Memory: A type of sensory memory related to scent information that lasts for two to four seconds. This kind of sensory memory is what allows you to still remember the smell of popcorn after you leave the movie theater. Although brief, olfactory memory often elicits strong emotional responses and can trigger long-term memories. If you smell pine, it may trigger a memory of you opening presents on Christmas morning with your family.¹ 

Multi-Store Model of Memory: A model of memory developed by cognitive scientist Richard Atkinson and his student, Richard Shiffrin, which suggested memory is composed of three separate memory stores: sensory memory, where information is processed for a few seconds, short-term memory, where information that we are paying attention to is held for 15-30 seconds, and long-term storage, which has a relatively unlimited duration.³ 

In the mid-twentieth century, psychologists were stumped by a problem of perception. Daily, people encounter vast amounts of information. Just consider the room you’re in right now. If you pay attention, how many things can you see, feel, hear, touch, or smell? However, even when you’re not focusing your attention, there are certain pieces of information that you are likely processing, even if later on, you wouldn’t be able to tell someone every sensory stimulus you encountered.  

In 1960, psychologist George Sperling set out to answer this question: Why do people seem to perceive more than they can report? He conducted a study where participants were exposed to a tachistoscopic stimulus—an image or word that is only presented for a few milliseconds—and asked to recall information. Participants were shown a 3x4 grid with twelve letters for around 50 milliseconds. Sperling then asked participants to participate in a “whole report” task, where they were asked to recall the entire grid, or a “partial report” where a tone that played immediately after the grid disappeared indicated whether they should recall the top, middle, or bottom row.

Participants were asked to participate in both the whole and partial reports so that a direct comparison could be made. In the whole report condition, participants remembered approximately 35% of the letters on display, around four letters. However, in the partial report condition, participants were able to reliably remember the entire row, with an accuracy of 75 to 100%. What Sterling inferred from these results was that all, or most, of the information had in fact been perceived, with participants taking in all twelve letters, as they were unaware which row they would have to recall in the partial condition. However, the information rapidly decays, which is why participants struggled to get more than 4 or 5 letters in the whole report.

The rapid decay was confirmed as Sperling conducted further tests, elongating the time between the flashing of the grid and the tone playing. In the initial condition, it was played a ⅓ of a second after the grid disappeared. When it was delayed a bit longer, participants’ ability to recall significantly declined, and when the time delay was over a second, participants virtually remembered nothing. Through this experiment, Sperling gained a better understanding of sensory memory, specifically related to visual stimuli.⁴ 

In 1967, German-American psychologist Ulric Neisser coined the term iconic memory to describe the brief sensory memory store for visual information that Sperling had researched. He also proposed that our brains must have the capacity to very temporarily store information that we hear, introducing the term echoic memory. In later years, researchers used a similar experimental design to Sperling to test whether people have the capacity to retain auditory sensory information and found that it is held in our sensory memory for two to four seconds.⁵

In 1968, cognitive scientists Richard Atkinson and Richard Shiffrin used the research that had been conducted to date on sensory memory to propose a multi-store model of memory. The model divides memory into three separate stores: sensory memory, short-term memory, and long-term memory. Atkinson and Shiffrin suggested that information is temporarily held through our senses in the first store, but for it to move to short-term memory, we must pay attention to it. Information in our short-term memory is held for approximately fifteen to thirty seconds and can then be transferred to long-term memory through rehearsal.³

Other types of sensory memory, each related to a particular sense, have continued to be researched and studied throughout the years, with developments in neuroscience and imaging technologies confirming that different sensory memory types activate different parts of our brain. 

George Sperling

An American psychologist who made significant contributions to our understanding of sensory memory through his experiments on visual memory, which showed that we store most of the information that we see, albeit very briefly, which is why we are able to recall less information than we actually perceive. Sperling had originally proposed the tachistoscope experiment in a student paper while he studied at the University of Michigan, and while he spent a summer working at Bell Laboratories, his supervisor arranged for him to carry out the experiment. His subsequent research focused on how attention impacts our visual perception and memory.⁶

Ulric Neisser

A German-American psychologist who coined the terms iconic and echoic memory in his 1967 book Cognitive Psychology, which discussed perception, attention, and memory. It was a departure from the dominant behaviorist lens at the time, where psychologists were only interested in what they could observe, shifting the focus to what was inside our brains. Neisser also introduced the reappearance hypothesis in this book, which suggested that people are able to recall highly emotional events with impressive accuracy.⁷

Richard Atkinson & Richard Shiffrin

American psychologists whose most impactful contribution to cognitive psychology was their development of the multi-store model of memory, which showed how information transfers between stores, starting with sensory memory and moving in a linear fashion to short-term and then long-term storage.³ Throughout his career, Atkinson was well-known for using mathematical models to explain complex psychological phenomena,⁸ whereas Shiffrin explored how attention impacts memory.

Sensory memory may be brief, but its influence is far-reaching. From improving how we learn to enhancing our experiences with technology and supporting recovery after brain injury, understanding sensory memory has helped shape real-world solutions across multiple fields.

Designing more efficient learning methods

A deeper understanding of sensory memory tells us that we have the capacity to process a lot of information from our senses, but that it decays very quickly if not paid attention to. This knowledge can inform how we teach to make it easier for people to remember information at a later date.

Some of our sensory memory can be encoded with other kinds of information when we learn it. A 1973 study by Akira Thomas and Endel Tulving developed the encoding specificity principle, which suggested that for a retrieval cue to be useful, it has to exist at the moment of encoding as well. If a teacher wants a cue, such as an image of an atom, to prompt students to remember how an atom is divided into electrons, protons, and neutrons, then they should present that iconic cue when teaching the students the information. Sensory memory that is encoded with other information might make that information easier to remember later.⁹ 

Thomas and Tulving’s principle was later supported by a study conducted by British psychologists D.R. Godden and Alan Baddeley, who showed that when the environment is the same during encoding and recall, people remember information better. In one study, divers either learned words on land or underwater and were then asked to recall the information either on land or underwater. The results showed that participants performed best if they learned the words in the same environment in which they were later asked to recall them (e.g., if they learned the words underwater, they recalled the information better when asked to repeat them underwater). 

These studies suggest sensory memory has a role to play in retrieving memory from long-term storage, which can inform the design of learning environments, by maintaining the same setting in which students learn as the one in which they later have to recall the information, such as exam rooms.¹⁰ 

Improving the user experience

Insights into sensory memory, particularly echoic memory, have been instrumental in refining user interface designs and auditory alerts in technology.

A 2024 study showed that echoic memory can improve the user experience. The study explored how better-designed sounds may improve the experience of workers using a warehouse management system, a software that supports workers as they scan inventory, search for items, or ship packages. Normally, simple beeps are used to indicate the success or failure of a task. The researchers designed better echoic feedback systems with more sophisticated sounds that helped workers more easily differentiate between success, failure, or intermediaries like warnings. The updated earcon system matched how our echoic memory works, lasting only about two to four seconds.

The researchers found that the workers who used the improved earcon system also reported having a better experience. It not only improved the success rate and allowed workers to complete tasks on time, but workers also reported a perceived lighter workload and reduced frustration and annoyance when completing tasks.¹¹ 

Designing technology that mimics the way that our senses process and store information can reduce cognitive load, improve performance, and lead to a better user experience. 

Advancing neurological rehabilitation

Research has shown that haptic memory (related to touch) can help in the rehabilitation of people with strokes. Individuals who have strokes often lose the ability to move certain parts of their bodies, but stimulating haptic senses can help to strengthen neural pathways from sensory memory to action, supporting the brain’s ability to relearn and regain motor control after a stroke.

In 2020, researchers developed a wearable stimulation device called a vibrotactile stimulation (VTS) glove that sent vibrations to the hands of stroke survivors. Sixteen stroke survivors who had reduced movement in their hands were asked to either wear the VTS glove for three hours daily over eight weeks, or an identical glove that had the vibration disabled. This control condition was included so the researchers could be sure it was the vibration, which may trigger haptic memory, that led to improved motor use of the hand.

After eight weeks, participants who had worn the VTS glove showed significant improvement in tests that evaluated the use of their hand and arm functions. The researchers concluded that consistent haptic stimulation can reactivate sensory traces in the brain and strengthen neural networks, helping patients to regain their motor skills.¹² 

Although sensory memory is widely accepted as a foundational part of how we process information, scientists continue to debate how it really works. From the role of attention to the independence of our sensory systems, ongoing research challenges traditional assumptions and reveals just how complex this fleeting form of memory may be.

Does attention matter for sensory memory?

Researchers who study memory are often interested in the role that attention plays in our ability to encode and recall information. Research has shown that attention is important for moving sensory information into our short-term memory—we can extend the time that we remember something if we are paying attention to it—but classical theory suggests that sensory memory is passive and does not require attention. However, as most of the studies that demonstrate sensory memory are administered under clinical conditions, it is difficult to say that people remember information without paying attention to it. As experiments occur in controlled lab environments, participants are more likely to be attentive due to the setting and perceived expectations of the researchers.

Additionally, recent research seems to indicate that attention does impact our sensory memory. A 2022 study interested in learning more about the role of memory conducted various experiments to see how distractions affected the amount of visual information participants could remember. In one study, participants were asked to remember visual information while they performed a challenging cognitive task. In another, they were given the same instructions while they were shown irrelevant visual information that served to distract them. In both types of experiments, participants’ iconic memory suffered, suggesting that attention actually does have a role to play in sensory memory.¹³ 

How long does sensory memory last?

Depending on the type of sensory memory, research suggests that it lasts between a fraction of a second and four seconds. However, studies have shown that sometimes sensory memory can be encoded, which improves later recall, begging the question of how long sensory memory really lasts.

While Sperling’s initial study suggested that iconic memory only lasts a quarter of a second, later research suggested there might be an intermediate kind of visual memory that sits between iconic sensory memory and short-term working memory. Researchers have called this intermediate memory fragile visual short-term memory (VSTM). Once again, the role of attention comes into question. Researchers believe that when attention is paid to visual information, it enables people to hold onto it for up to four times longer than iconic memory, as fragile VSTM. Research into fragile VSTM not only challenges our assumptions of the duration of our sensory memory but also the multi-store model of memory, which suggests that there are only three different types of storage.¹⁴

How different are the types of sensory memory? 

While researchers generally agree that each of our senses has a different sensory memory system, there is some debate about how independent, or interconnected, they are. 

Evidence from fMRI scans reveals that different parts of the brain are activated by different senses, suggesting they are independent systems. For example, haptic memory is thought to use the parietal lobe, while echoic memory activates the temporal lobe. Moreover, each type of sensory memory is thought to have a different duration, and some kinds, like olfactory, elicit stronger emotional responses than others.¹⁵ 

On the other hand, case studies of patients with synesthesia, where the experience of one kind of sensory memory triggers another (for example, associating particular sounds with colors), suggest there is some level of interconnectedness between types of sensory memory.¹⁶ Findings from a 2014 study also suggest that the various types of sensory information use a shared pool of memory resources. 

The study asked participants to complete two different types of tasks: iconic and echoic. Participants had to remember visual information like patterns, and/or auditory information like the pitch or length of a sound. The more information they were asked to remember, the worse their sensory memory became. This was true regardless of whether they were asked to remember only visual or only auditory information. This suggests that our brain uses a shared pool of memory resources for sensory information, which means that if we are concentrating on one kind, we have lower capacity for the others.¹⁷ 

The emotional impact of olfactory memory

Have you ever smelled someone’s laundry and vividly remembered what it felt like to hug them? Or smelled a dessert that triggered a memory of your grandma’s blueberry pie? I bet every time you put on sunscreen, it conjures up crystal clear memories of summer fun. 

That’s because olfactory memory—memories related to smell—have the capacity to elicit vivid, emotional memories to a greater extent than other sensory memories. That’s why scent branding (where companies like hotels have signature scents present in all of their destinations) is so popular. Hotels want to elicit certain emotions, like calmness or elegance, during your stay through signature scents that cause you to associate those feelings with the brand.¹⁸ 

The first study to show the link between olfactory memory and emotion was in 1992 by psychologists Rachel Herz and Gerald Cupchik. In the study, 20 female and 20 male participants were divided into two groups. One group underwent the subjective condition, where they were asked to approach a smelling task with an emotional mindset. The other group participated in an objective condition, where they were asked to approach the task with an analytical mindset. All participants were then asked to rate twenty different odors based on pleasantness, familiarity, intensity, arousal, and degree of interest. They were also instructed to try and guess the odor, and if a personal memory came up while smelling it, they were asked to briefly describe the memory.

Herz and Cupchik found that the memories that were evoked were very vivid and specific, especially for the subjective condition. Thirty-two percent of the time, participants had a personal memory attached to the odor without being able to name the scent, showing that a verbal label wasn’t necessary to evoke strong emotion. They also found that women were able to describe memories with more clarity and detail than men.¹⁹ The study provided evidence that odors are triggers for emotionally rich and vivid personal memories, and when compared to studies that researched the affective response to other sensory memories, suggested that olfactory memory can trigger more emotional responses than other senses. 

The man with an “impossible” memory

In 1968, Russian neuropsychologist Alexander Luria wrote about one of his patients, Solomon Shereshevsky, a thirty-four-year-old journalist with an incredible memory. Shereshevsky was able to recall almost every single detail of his life. While at the time, psychologists did not have a word to describe Shereshevsky’s case, we now know that he suffered from hyperthymesia—the ability to remember the vast majority of personal experiences.²⁰ This was first discovered by Shereshevsky’s boss at a Moscow newspaper, after he confronted the journalist for not taking any notes when daily assignments were given. Shereshevsky told his boss he didn’t need to because he remembered everything. Skeptical, his boss asked him to repeat everything that he had read in a newspaper to him. Shereshevsky was able to do it without making a single mistake, prompting his boss to suggest he get his brain examined.²¹ 

What Luria discovered was that Shereshevsky also had a condition called synesthesia, where stimulation of one sensory modality leads to an automatic experience in another. For example, when Shereshevsky saw a number, he also saw an associated color. The cross-modal sensory experience improved his memory retention, highlighting the intricate connections between sensory input and memory storage.

While hyperthymesia might seem like an incredible ability, it actually caused Shereshevsky a great deal of trouble. Shereshevsky could not control his memory, and when one of his senses was activated, it would cause memories to be retrieved spontaneously, which made it difficult to focus on tasks. This constant flow of memories was actually exhausting and made it hard for Shereshevsky to stay focused on the present. However, his case, as well as other cases of hyperthymesia and synesthesia, demonstrate the powerful impact that sensory memory can have on retrieval.²⁰ 

Blue Cars, Robots, and How Your Brain Chooses to See

While classical theory suggests that sensory memory is a passive experience, more recent research has shown that attention has a role to play in determining what information from our environment we store. Often, if we are looking to find particular stimuli, we’re going to pay more attention to it in the environment, which in turn, makes it seem like we’re seeing, hearing, or smelling it with much greater frequency than before. In this article, our writer Preeti Kotamarhi explores the impact of top-down attention and bottom-up attention, which filter the sensory information we encounter, impacting what we notice and what we ignore. 

Episodic Memory

Research has shown that olfactory memory—information that we get from smell—can trigger very intense, emotional memories. It has also been demonstrated that when we experience very emotional events and personal experiences, we can better recall the information. In this article, we explore the nature of episodic memory, which is defined as information about personal experiences that is stored in our long-term memory.

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