The 3 Types Of Sensory Memory: Iconic, Echoic And Haptic
There are many different hypotheses about the functioning of human memory that frequently 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.
Sensory memory allows us retain information obtained through the senses for a short period ; Subsequently, these signals will be discarded or transmitted to other longer-term memory stores, working memory and 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 short record of unlimited and precategorical capacity, that is, prior to the cognitive processing of information and consequently foreign to 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 the conscious processing of the most relevant items.
In its original formulation Neisser considered that there are two types of sensory memory: the iconic, which processes visual information, and the echoic, based on auditory and verbal stimuli. Subsequently, solid evidence has been found in favor of the existence of haptic memory, related to touch and proprioception.
Although it is considered that there are probably short-term memory stores for all the senses, those that have been studied in greater depth are iconic, echoic and haptic memory
1. Iconic memory
The most researched type of sensory memory is iconic, which records visual information. The most relevant contributions to this phenomenon were made by George Sperling in the 50s and 60s, but later authors such as Neisser, Sakkit and Breitmeyer have updated the conception of iconic memory.
Through his pioneering tachistoscope studies, Sperling concluded that people we have the ability to retain 4 or 5 items simultaneously after fixing your gaze for a moment on a broad stimulating set. Other researchers found that iconic memory persists for about 250 milliseconds.
In this case The visual trace is called “icon” that we keep in short-term memory. Currently there is debate about whether this icon is located in the central or peripheral nervous system; In any case, the conception predominates that iconic memory is fundamentally a laboratory artifact without ecological validity.
Most likely, this phenomenon is related to the persistence of neuronal stimulation in photoreceptors located in the retina, that is, the cones and rods. This system could have the function of allowing the processing of visual stimuli by the perceptual system.
2. Echoic memory
In a similar way to iconic memory, echoic memory has been defined as a precategorical record, of short duration and with a very high capacity. It differs from the iconic one in that it processes sound information instead of visual information.
The echoic memory retains auditory stimuli for at least 100 milliseconds, allowing us to discriminate and recognize sounds of all types, including those that make up speech, which can be maintained for up to 2 seconds; Therefore, echoic memory is fundamental in the understanding of language.
It is understood that this type of memory records auditory information in sequence, therefore focusing on its temporal properties. In part, the length of time the echoic trace is retained depends on properties of the stimulus such as complexity, intensity, and pitch.
A notable phenomenon in relation to echoic memory is the recency effect, which is specific to this type of memory. It consists of the fact that we remember the last stimulus (or item) that we have processed better than others that have been presented immediately previously.
Echoic memory has been related to the hippocampus and different areas of the cerebral cortex: the premotor, the left posterior ventrolateral prefrontal, and the left posterior parietal. Lesions in these regions cause deficits in the perception of visual stimuli and the speed of reaction to them.
3. Haptic memory
This concept is used to designate a memory store that works with tactile information, and therefore with sensations such as pain, heat, itching, tingling pressure or vibration.
Haptic memory has a capacity of 4 or 5 items, like the iconic memory, although the footprint is maintained for longer, 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 stimulation of the skin, and on the other hand the proprioceptive or kinesthetic, related 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 about this type of sensory memory is more limited than that which exists about the other two that we have described.
haptic memory depends on the somatosensory cortex, especially from regions located in the superior parietal lobe, which store tactile information. Likewise, the prefrontal cortex, essential for movement planning, also seems involved in this function.
