Kosslyn Computational Model

Kosslyn’s model goes and meets Paivio’s model in many ways. According to Kosslyn, our mind possessess two permanent information storages: images and propositions.

Via the images storage you will find information about the object’s form (through images) and through the propositional one, you’ll find the object’s meaning. These two types of representation are separated, however, they must join up in order for us to be able to represent the object in our minds.

For Kosslyn, images are represented in a spacial medium, with a limited capacity. It provides us the ability to deal with spatial relationships and object rotation, but the information depends on some perspectives.

For example, in a 1975 study, Kosslyn asked the subjects to imagine a rabbit and an elephant. Then, he asked them to imagine a rabbit and a fly. The rabbit had way more details in the second condition, because it’s the larger animal and our representation acts accordingly to that fact.

Two levels of image representation

According to Kosslyn, the image representation has two components, a superficial representation and a deep one.

The deeper representation is the stored information in Long-term Memory, from which the superficial representations branch out. These ones happen at visual level in the active memory.

In deep representation, the images could be subdivided in literal or perceptive appearance of the object and the list of propositions describing the object.

In conclusion, looking at a practical example: an image of the country’s president implies both the existence of an image and a proposition, in this case the presidency.


Paivio’s theory of dual coding

According Paivio’s theory, people use two systems of Mental Representation. They are independent from each other, yet connected. They are the verbal system and the non-verbal system and this is the basic assumption of Dual Coding Theory.

Each one of these systems has different types of information. Paivio defended that the non-verbal system deals with images and its equivalents in other sensory organs, while the verbal system dealt with the language processing. But, as I stated above, theses two systems are connected and each and any concept is associated to other concepts, in both systems, at the same time.

In 1971, a memory test was made in order to support this theory and provide some answers about this dual coding system. A long list of words and photos was given to the test subjects for memorizing. The results were unanimous: the subjects always recalled more photos than words.

In order to understand these results, some comparisons and analysis were required. First off, it was necessary to compare the verbalizable photographs with the non-verbalizable ones, as well as, the words that were more or less imagetic.

The differences between the subjects who were told to build a mental image for any presented word and the ones who were not instructed in that way were also analyzed.


General Conclusions

Cognitive performance is mediated by two interrelated systems which are different in structure, organization and information representation. In the verbal system (logogens) the information is represented in an abstract, logical and sequential manner, while in the non-verbal system, the representation is made through images in a concrete and analogical manner.


Coding Redundancy

Paivio studies’ show that the mnesic performance increases directly with the quantity of alternative codes in memory, which means, that if you can make the subject memorize a piece of information in the two systems of representation, the probability of him recalling it increases.

Although, these studies also show that if you give the test subject the information in a single code and ask him to create a second one, it will interfere with his memory capacity, which hypothesizes that sometimes, dual coding some sort of information can just be redundant.


Some modern neurocognitive studies support this theory.

What is Imagery?

A concept born with Aristotle, imagery can be defined imagery as an internal ability to represent images. However, in truth, imagery is much more than that. It’s a way of thinking which involves your senses in your thought process. It’s the ability of creating an image in your mind that you can see, hear, feel, smell or taste.


It’s an implicit system of codification that you use as an instrument in order to recover information about physical properties and relationships among different objects.

There are several different areas of investigation in regards to imagery. Scientists have long been focused on: imagery as a material’s property or attribute, as a cognitive process, as a personal experience (due to the fact that the vivacity of the internal images differs from person to person) and even imagery as a mental representation.

You need former experiences to produce internal images from external stimuli and those will allow you to describe the object or place. Maybe even allow you to describe a more complex scene that you’re seeing in your mind.

But, since we’re talking about something so subjective, the data must of course be obtained through verbal reports from the study subjects.

This whole concept of imagery includes two types of representation: analogical and propositional. In analogical representation we’re talking about the perception, or in other words, the image that arrives at your retina with all of its sensory qualities. The propositional representation however, includes no perception, being the images’ descriptions of the different visual scenes.

Marr’s Theory of Vision

David Marr (1945-1980), British neuroscientist and physiologist, developed one of the most known theories about the way our vision works. According to him, we receive an input in a similar way to an image in our retina, and this will then be processed by our brain in three different steps.

Primal Sketch

When you first receive an image of an object, your retina makes a simple register of the light intensity in each point of said image. That’s when you start detecting the vertices, the boundaries between objects, shapes, spots of union… Resuming, you get the fundamental points of the object, but not the depth or textures yet. This primal sketch is totally dependent on which perspective the object is presented to you at.

The 2.5D Sketch

The second step is still dependent on the perspective in which the object is presented to you at, yet, now you have more information to work with, such as the textures as well as depth and you can start to see how the visible surfaces of said object relate to each another.

3D Model

In this last step, you’ll be able to get the information which is not dependant on the perspective. These representations are built from the visual inputs and compared with the representations stored in your Long-term Memory. At this point is where object recognition will take place.


Marr’s theory is able to tie together the initial vision and the eventual object recognition, providing us a theory that can explain the whole system of recognition and identification of objects and patterns visually presented to us.

Perception: What you see and what you think you see

Perception is the significance you give to what you see or feel, the stimuli you receive from your senses, the significance you give to the objects, the way you see or feel them and the way you put them into space.

Vision is a very important sense for most of the people, it’s through your eyes that you’ll recognize the world and receive information. However, you must be able to represent this information or it won’t be enough.

In order to recognize an object, there are a lot of systems working closely together in your mind and, sometimes, all it takes is a change in perspective for you not to be able to recognize a once familiar object. So, what makes you recognize the objects and the world around you?

Perception refers to a representation of stimuli based on a pattern, it will provide us the possibility of recognizing an object and detect its location in the space. It’s an active process of our mind, where our former knowledge and information are used for the recognition of other object and entities.


Visual Cognition

The visual recognition is, as you might imagine, quite complex, so what are the cognitive processes involved in it?

There are three major theories that try to explain the way our brain makes these recognitions: Template-matching Theory, Conceptual Categories and Structural Models.

According with the Template-matching Theory, you have images from all objects in your mind and when you receive any new stimuli, you’ll search your memory for an image that matches with the current one. As you see it’s a very simple theory (too simple) and because of that, it raises a lot of questions. It cannot explain how you recognize an object given a specifically unfamiliar perspective or how you process such a large amount of information so quickly. It’s inflexible and inherently flawed.

The Conceptual Categories Theory talks about concepts that will be mental representations of the objects. According to this theory, our brain will group the concepts into categories, which can be subordinated from one another. The subordinated categories will inherit the properties of superordinate categories and have some new properties of their own.

This theory isn’t free of problems and one of the major ones is the lack of formal definition from some of its concepts and the very thin lines and frail differences between some of the aforementioned conceptual categories.

In regards to Structural Models, there are two main theories here, the Geon Theory and the Recognition-by-Components Theory, both by Biederman. The Geon Theory defends that there are primitive forms which are regrouped according to specific rules and the object is the spacial arrangement of its geons, as you can see in the image below. It’s a very simple theory and, because of that, reductive in its nature.

So, Biederman elaborated the Recognition-by-Components Theory (RBC), according to which, our brain will detect the non-accidental properties (the ones that do not change much, even given different perspectives) of the object and its concavities. From these two elements, the human brain will be able to determine the components which will be compared to the object representations in our memory.

Long-term Memory

Long-term Memory is the one that makes it possible for you to recall a face, a place or your own pet, when you see them. The information stored in here, remains for a life-time and its storage capacity is endless.


Working with Long-term Memory

Long-term memory is the most complex of all memory types. There are different forms of working with it, for it and within it.

Repetition, for example, is a way of getting Long-term memory and short-term memory to interact with each other. It will allow the information’s transference from Short-term to Long-term, at the same time that it also helps the Long-term storage information to be able to also have a place and remain in the Short-term where it’s easily accessed.

Another way of working with it is through coding, which basically equates to giving some meaning to the pieces of information in order to make them easier to remember. This will help the recuperation process which is, according to some authors, the component which is truly responsible for our inability to recall certain memories.

Different Memories in one Memory?

But, speaking about Long-term Memory isn’t that simple, and different authors have presented different theories. Long-term Memory allows us to be who we are, it’s a permanent storage of knowledge and information, and it will have a great impact in the way we perceive the world around us.

There are many theories around Long-term Memory, but the one which seems to be the most widely accepted is the one that divided Long-term Memory into two separated sections: declarative memory and procedural memory.


Declarative Memory

Declarative memory refers to facts and situations that can be recalled, as in, we can say what happened or took place, how something looks or feels like… It’s something conscious and that gives us the possibility of expressing it. This can, by itself, be divided into episodic memory and semantic memory.

Episodic memory refers to particular events and specific episodes we lived and we’re now able to remember with surprising detail. It’s linked to an event or specific occasion.

Semantic memory is more about knowledge and the significance that we attributed to something. Here, the knowledge is stored under a form of words and symbols, and it contains general knowledge about the world, about facts and not particular events.

Procedural Memory

Also known as implicit memory, procedural memory doesn’t really imply an active and conscious effort from us. It’s related to motor or cognitive skills that are automatically brought up in order to do or achieve something, like playing a guitar or driving a car.

It also reflects, for example, grammar acquisition. You can speak correctly without being able to explain why it is indeed correct. The classical conditioning is associated to procedural memory too, since you can’t, for example, consciously explain why you fear elevators.

This kind of memory can be affected by abnormally high levels of stress. In these occasions we seem to forget, temporarily, how to do something that we’re usually able to do very easily.


So, if it lasts a life-time, why can’t you remember everything?

As you may be thinking right now, you can’t remember everything you want to, at least, not exactly as it happened. There are some gaps here or there. Well, that’s totally normal.

There are many diseases that can affect long-term memory, such as Alzheimer’s, Dementia, Schizophrenia or Parkinson’s, but even a perfectly normal and healthy adult can’t recall anything he or she wanted. For example, it’s quite normal for an adult to remember with more intensity and details, events that occurred during adolescence that those during his middle-age. Maybe because, teenagers live everything with amplified intensity and when you are older you give less and less importance to some situations and they kind of fade away in your memory.


Flashbulb Memory Theory

Brown and Kulik (1977) developed some investigation in this area, regarding episodic memory, where they tried to prove that emotions could indeed affect our memory.

They centered their investigation in specific historical events and asked people how they remembered it (the most famous experiment being how they remembered the news about John Kennedy’s death). These memories were too vivid and had many details, but they weren’t accurate…

The fact is, that a vivid and detailed memory doesn’t mean a correct description of the event, because memories (specially the older ones) are thought of, repeated and elaborated by our mind, especially if they had a great emotional impact. Our brain will mix what really happened with what we think happened and what we think should had happened.

So, most of the time, these memories are very far-off from the reality of the described event. They are like flashes of a camera that pops up in our mind and we interpret them accordingly with the importance and distinctiveness of the event, its consequences, how surprised we were and the proximity and personal involvement with the event.

Short-term Memory

Short-term memory refers to memories which remain for around 20-30 seconds. It’s a very short time-frame and there’s limits to the amount of them as well. Some experiments performed by Petersen and Petersen (1959) suggest that the maximum capacity of Short-term memory is around 7(+/- 2) chunks of information (also called The Seven Plus or Minus Two Theory).

However, this is something really difficult to measure, due to the significance that an information may or may not have for a person. For example, four random numbers can be four pieces of information, but they could also be a date which might mean something for a specific person, so it will become just one piece of information for such an individual, and so, theoretically, that person would be able to remember more pieces of information that another one, for whom the numbers didn’t get memorized as a date, since it didn’t mean anything to them.



Based on this information, scientists determined chunking as a method to improve our Short-term Memory capacity. Giving some meaning to the information, as well as a favorable context of learning, a subject would be able to retain a somewhat larger amount of information.

In the same way, giving some tips to the subject, would improve his or her ability to recall the information.


Serial Position Effect

There are a lot of circumstances that can affect our Short-term memory capacity and the serial position is definitely one of them.

Some experiments revealed that when some words are presented in a row, or sequence, the subject tends to remember more efficiently the first ones (primacy effect) and last ones (recency effect), while the ones in the middle of the series are frequently forgotten.

This can have some practical implications, as, for example, it could be the explanation for the fact that the first impressions you have, regarding other people, can have such a great impact on your perception of them.