Rigid and attenuated filter models: what do they say about attention?

People are constantly subjected to very complex situations in which a large number of stimuli compete for our attention. Although we don’t realize it, we spend a lot of time picking out the relevant from the unnecessary, separating the grain from the chaff.

This is mainly because our resources to process information are very limited, so if we opened the barrage of our attention without any control, we would end up feeling how overwhelmed the ability to understand what is going on around us would be overwhelmed. .

In order to find out how our brains work in situations as frequent as this, a series of assumptions have been postulated throughout the 20th century that would mark the way forward over the years. Among these, the rigid and attenuated filter model was the pioneer.

In this article, we will discuss the postulates of this classic model, with particular emphasis on the different points that information passes through from the moment it is perceived by the senses until it is persistently stored in the body. memory.

    Rigid filter model and attenuated filter model

    The rigid filter model and the attenuated filter model offer a dynamic of the functioning of attention that is distinguished by insertion of a filter or screening mechanism, Thanks to which the complexity of the environment would be purified and the relevant elements would be selected. It includes elements of multi-store memory theory, prior knowledge is fundamental for the proper understanding of these models: sensory storage, short-term memory and long-term memory.

    1. Sensory storage

    Sensory storage is the first stop in information processing, because it is the space in which the sensations of the sensory organs are deposited.

    The perceptual fact, through one of its different modalities (visual, acoustic, olfactory, taste and tactile), needs little time to be picked up by the nervous system, but it requires a little more elaborate analysis to determine its physical properties and its nuances.

    In this warehouse, of very large capacity but of very limited duration, an extraordinary volume of elements settles on the situation in which we find ourselves, even if almost all of them are diluted in a few seconds (without analysis cognitive depth). The information would be transferred from here to short-term memory, after being sifted through the attentional filter, Which will be discussed in detail later.

    2. Short-term memory

    Once the information from the senses has passed through the aforementioned sensory memory, it would be projected into short-term memory. At this moment an abstraction of the sensory image is preserved, A kind of interpretation of the object on which attention has been placed.

    This interpretation is an inaccurate picture, because he underwent a first process of cognitive elaboration in which some of its objective properties may have been altered.

    This memory has a smaller amplitude than sensory memory, but its duration is much longer. Thus, the (now conscious) retention of this data may last a few minutes, but will tend to dissolve if deemed irrelevant by the receiver. In general terms, it is estimated that an individual (under normal circumstances) can retain up to seven single items at this stage of processing, with the normal range being three to eleven.

    Anterograde amnesia provides reliable information about the very existence of this store, and is one of the most common arguments used by supporters of memory compartmentalization. This phenomenon describes the formation of new learnings that only last a few minutes, After which they disappear without consolidating in any case (so they will never enter the warehouse in the long term).

      3. Long-term memory

      When the information has been perceived by the sensory organs, sent to sensory memory and derived from short-term memory, there is a process of conscious analysis of its importance in order to transfer it to the last station: memory to long term. It is in this place where distant declarative memories live, And to which we voluntarily turn when we wish.

      Long-term memory has an indefinite duration and can last a lifetime. Here is stored a declarative crystallization of lived events (episodic), knowledge of the world (semantics) and acquired skills (procedural); all of this is necessary for its emotional relevance and / or adaptive value. There are many brain regions involvedIt is therefore usually affected during the course of dementia processes.

        Filter models

        Once known the different warehouses in which the memory is divided, and after the analysis of its process from the moment when the object is captured by the senses until it is finally stored in a lasting way, it is easier to understand the model. and filter attenuated. These theories were developed in order to understand the way a human being handles complex situations in which a wide variety of information competes to be perceived, processed and stored.

        Thus, he explores the characteristics of selective attention: how to discriminate information from the environment when it is complex, in order to collect relevant and articulated responses appropriate to the context. We will come back here to two pioneering hypotheses on this subject: the rigid filter (Donald Broadbent) and the attenuated filter (Anne Treisman), Being at the same time the theoretical foundation on which would be built the subsequent theoretical elaborations (like the late filter model or others).

        To get a better idea of ​​these models, the most useful is to set an example: imagine meeting a friend in a bar, having a coffee, while telling us an interesting story. How do we draw attention to their words if the atmosphere is awash with other sounds that compete with them (like people talking, dragging cutlery, and even cars driving near us)?

        In order to explore what happens to our brains in everyday situations like this, the authors used an experimental-type procedure called dichotomous listening, And which consists of the simultaneous transmission of two different messages through each of the ear canals (using headphones). The participant would sit down and listen to its content (numbers, words, etc.) and, after the presentation, underline what he thought he had perceived.

        With this simple method, the dynamics of selective attention could be exploredOne of the expressions of this executive function, which consists in the choice of a relevant stimulus and the omission of ignoring it when both are presented at the same time. It is a basic skill for the development of activities of daily living, alongside sustained (or vigilant) and divided attention (effective approach to two or more important tasks at once).

        While it is true that Broadbent and Treisman agreed on the basics, such as the existence of sensory memory and the process of transmitting information from short-term memory to long-term memory, they showed related discrepancies. With the concept of “filter”. In both cases, its existence was considered as a phase of pre-screening of the complexity of the stimulus, But different views related to its degree of permeability have been maintained (as will be seen later).

        1. Rigid filter model

        Using a filter might sound like, in Broadbent’s own words, “the neck of a bottle”. If the stimulation field in which we find ourselves can be very complex, our cognitive capacities only allow us to process and analyze a discrete percentage without exceeding the resources at our disposal. For this purpose, the filter would act as a sieve of environmental diversity to translate it into clear, operational and manageable terms.

        This filter would be localized, according to the author (although it was later questioned under the Deutsch and Late Deutsch filter), just at the end of sensory memory and before short-term memory. In this way, the stimuli would be transformed in series, and never in parallel (which implies that the information is analyzed one at a time and never simultaneously). This filter facilitates a selection of the relevant and the irrelevant, so that the former transcends short-term memory and the latter is drastically omitted.

        According to Broadbent, the selection criterion would be the physical property of the stimulus, Like the tone or volume of the human voice, as well as the unpredictability with which it bursts into the perceptual field. Either way, from these variables, the individual would choose what is relevant to him, while the rest of the elements would be completely ignored without being addressed or understood.

        Broadbent provided empirical evidence through dichotomous listening, through an experimental condition consisting of the emission of a brief list of numbers in each of the assessor’s ears. For example, if you listened to the sequence 947 in your left ear and 246 in your right ear, you would remember only one or the other (but never information combining the two sources or all the elements included in the list. ‘trial). He concluded that each of the ears would function as an independent channel, choosing only one of them and omitting the other altogether.

        2. Attenuated filter model

        The attenuated filter was proposed by Treisman, after his attempts to replicate Broadbent’s findings. Between the proposals of these two authors, there is a fundamental difference, located precisely in the qualities of the filter as an element inserted in the processing of information.

        Treisman considered that there was no absolute blockage of the unattended stimulusBut it was handled in a certain way even though the person was trying to focus on the relevant. Unattended messages would be reduced in importance, but they would not go away.

        Like Broadbent, he used dichotomous listening to test his hypothesis. In this case, verbal messages (meaningful sentences) were used, but dividing the informative segments in a particular way.

        For example, two messages without a logical connection would be read successively through the left ear (like “I caught a coat, we caught 4 fish”), while in the right a sound would be very similar in terms of structure ( “we go fishing because it was cold”). In this case, the person said he heard “I grabbed a coat because it was cold” or “we went fishing and caught 4 fish”, proving that I had listened to both messages at the same time.

        The explanation for this discovery by Treisman was that the filter does not completely replace the unexpected messageBut this is still being processed at some level and may attract attention if it brings congruence to what was perceived up to that point. He also showed, for example, that people remembered basic aspects of ‘ignored’ information, even using Broadbent’s own paradigm (changes in voice volume, timbre, tone or gender of the voice). speaker, as well as the reproduction of the name of the subject being evaluated).

        Thus, certain conditions of the individual (such as his life experience or future expectations) would be responsible for assigning perceptual relevance to the stimulus. In addition, the filter would act by weakening the less relevant messages, but these would not be completely inhibited (as suggested in the hard filter). There would therefore be a basic processing at the semantic level (Pre-categorical type) which would optimize selection tasks without saturating the cognitive system.

        Bibliographical references:

        • Pilot, J. (2001). A selective review of selective care research from the last century. British Journal of Psychology, 92, 53-78.
        • Lee, K. and Choo, H. (2011). A critical examination of selective attention: an interdisciplinary perspective. Journal of Artificial Intelligence, 40 (1), 27-50.

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