The 3 types of sensory memory: iconic, echoic and haptic.

The brain has different processes that make it possible to memorize specific aspects of the environment.

There are many different hypotheses about how human memory works and they often overlap with each other. In recent years, research has clarified key aspects of sensory memory, one of the oldest concepts in the field of scientific psychology applied to this basic process.

In this article we will define the characteristics of the three main types of sensory memory that have been described to date: iconic, echoic and haptic memory, which work with visual, sound and tactile stimuli, respectively.

What is sensory memory?

Sensory memory allows us to retain information obtained through the senses for a short period of time.Later, these signals will be discarded or transmitted to other memory stores of longer duration, the working memory and the long-term memory, through which immediate stimuli can be operated on.

The concept "sensory memory" was coined by Ulric Gustav Neisser in 1967. His model was based on basic research and defined sensory memory as a register of short durationIt is a record of unlimited capacity and pre-categorical, i.e., prior to cognitive processing of information and therefore beyond conscious control.

Previously, in 1958, Donald Eric Broadbent had proposed the existence of a perceptual system through which all sensory stimuli would pass before reaching short-term memory and being filtered for conscious processing of the most relevant items.

In his original formulation Neisser considered that there are two kinds of sensory memoryThe iconic, which processes visual information, and the echoic, based on auditory and verbal stimuli. Subsequently, strong evidence has been found in favor of the existence of haptic memory, related to touch and proprioception.

Types of sensory memory

Although it is considered that there are probably short-lived mnemic stores for all the senses, those that have been studied in greater depth are iconic, echoic and haptic memory..

Iconic memory

The most researched type of sensory memory is iconic memory, which records visual information. The most relevant contributions on this phenomenon were made by George Sperling in the 1950s and 1960s, but later authors such as Neisser, Sakkit and Breitmeyer have updated the conception of iconic memory.

Through his pioneering studies with tachistoscope, Sperling concluded that people have the ability to simultaneously retain 4 or 5 items after gazing for a moment after gazing for an instant at a large stimulus set. Other researchers found that iconic memory persists for about 250 milliseconds.

In this case the visual trace that we retain in our short term memory that we retain in short-term memory is called an "icon". There is currently debate as to whether this icon is located in the central nervous system or in the peripheral nervous system; in either case, the prevailing view is that iconic memory is primarily a laboratory artifact with no ecological validity.

Most likely, this phenomenon is related to the persistence of neural stimulation in the photoreceptors. neuronal stimulation in the photoreceptors located in the retina, i.e., in the located in the retina, i.e., the cones and rods. This system could have the function of allowing the processing of visual stimuli by the perceptual system.

2. echoic memory

Similar to iconic memory, echoic memory has been defined as a pre-categorical register, of short duration and with a very high capacity. It differs from iconic memory in that it processes sound information instead of visual information.

Echoic memory retains auditory stimuli for at least 100 milliseconds, allowing us to discriminate and recognize them.It allows us to discriminate and recognize sounds of all kinds, including those that make up speech, which can be retained for up to 2 seconds; therefore, echoic memory is fundamental in language comprehension.

It is understood that this type of memory records auditory information in the form of a sequence, thus focusing on its temporal properties. In part, the length of time the echoic trace is retained depends on stimulus properties such as complexity, intensity and pitch.

A remarkable phenomenon in relation to echoic memory is the recency effect, which is specific to this type of memory. It consists in the fact that we remember better the last stimulus (or item) that we have processed than others that have been presented immediately before.

Echoic memory has been related to the hippocampus and to different areas of the cerebral cortex: premotor, left posterior ventrolateral ventrolateral prefrontal and left posterior parietal. Lesions in these regions cause deficits in the perception of visual stimuli and in the speed of reaction to them.

Haptic memory

This concept is used to designate a mnemonic store that works with tactile information, and therefore with sensations such as pain, heat, itching, tingling, tingling, etc.The haptic memory has a capacity of 4 or 5 items, like the iconic one.

The haptic memory has a capacity of 4 or 5 items, like the iconic memory, although the trace is maintained for a longer time, about 8 seconds in this case. This type of sensory memory allows us to examine objects by touch and interact with them, for example to pick them up or move them appropriately.

It is believed that there are two subsystems that make up haptic memory. On the one hand we find the cutaneous system, which detects skin stimulation, and on the other the proprioceptive or kinestheticrelated to muscles, tendons and joints. It is important to distinguish proprioception from interoception, which involves the internal organs.

Haptic memory has been defined more recently than iconic and echoic memory, so the scientific evidence available for this type of sensory memory is more limited than for the other two described above.

Haptic memory depends on the somatosensory cortexespecially regions located in the superior parietal lobe, which store tactile information. The prefrontal cortex, which is essential for movement planning, also seems to be involved in this function.