in this lecture Iordanis Kavathatzopoulos provides a brief description of the main characteristics of perception theories. The purpose is that you should get an understanding of the basics of perception and the research in the area, and how the results can be applied in IT design.
Perception is the basics of all our knowledge about the surrounding world. Our perception comprises our abilities to take in information through our senses. Without these abilities we would not be able to perceive what happens in the outside world. Perception is also one of the basics of human-computer interaction. By means of our perceptual system, we take in the information provided by the IT system and use that to interact with the system. However, the matter is not so simple. We cannot take in all the information that is presented on the screen and available in the surroundings. Our perception is flexible, but also limited in some ways. For instance, we can discern objects when light is poor, and we are able to perceive rapid movements in our peripheral field of vision. On the other hand, our ability to perceive small changes, e.g. events that evolve very slowly, is limited. Nor can we perceive all the colours in the colour spectrum. Therefore, it is essential to conduct research on our perceptual processes so that they can be explained and understood. Information from the outside is, for instance, not directly perceived and understood. We have internal structures that process the perceived information and make it comprehensible to us.
We have to identify and analyse the perceptual structures in order to understand what information will be perceived and how. That knowledge is necessary when designing the presentation of information in IT systems, so that the users perceive it correctly. There are a number of different theories regarding these structures. Are they, for instance, innate or acquired, i.e. do we have them at birth, or are they created subsequently. Is it possible to influence these structures (in users) to change them to better fit the IT system? Do these structures perceive the information, or do they process it and restructure it? We do not know, and there are different theories providing different explanations and models of these structures.
Our different sense organs perceive different types of input in accordance with the structure and complexity of the organ. We perceive auditory input through the ears, and visual input through the eyes. There is, however, also a certain limited degree of inter-modality. We can, for instance, "see" softness or "hear" hardness. Nevertheless, the different sense organs are tuned into and optimised for a certain type of input.
The internal psychological structures also control our attention and the interpretation of the information we perceive. There are, for instance, numerous examples of witnesses recounting the same event in widely different ways, each one interpreting the event in his/her own way.
People use different cognitive styles to direct their attention.
We are constantly surrounded by great amounts of sensory input. For instance, right now, you are reading these lines, at the same time you may hear a car pass by outside your window, you may be aware of the chair you are sitting on, you may be aware of the colours used on this web page, etc. The amount of sensory input is infinitely large. And you select that input to which you want to pay attention. All the sensory input is there, always, regardless of whether or not we pay attention to it. But we pick out a minor part of it and attend to that. Our attention is thus highly selective. Having a non-selective attention would make life impossible. We would drown in information.
We can use different cognitive styles for directing our attention. Either, we can passively perceive or receive the input from the surroundings. Or we can actively seek out and take in the information we need for a particular purpose or for solving a particular problem. A captain of a ship, for instance, can either choose to look at the beautiful archipelago passing by or actively check out the wave height, the shoreline and navigation marks.
Attention involves a mental and physiological activation of the organism. The heart rate, brainwaves, skin resistance and pupil size all change when attention is activated. Mentally, attention involves an increased readiness for information processing.
However, at sudden events our orientation is automatically directed toward the event and our attention is triggered almost instinctively by the event. In such cases, attention is not a result of a conscious effort. At other times, we want direct our attention to a particular event or object. We want to avoid distractions and irrelevant information. If we are successful at this, things move on smoothly, we become absorbed in what we are doing. But, often it takes an effort to concentrate on and direct the attention at what we are doing.
Attention is selective. We continuously select the information input on which we want to focus. One example of selective attention is the cocktail party phenomenon. At a cocktail party there are lots of people and lots of talking and laughing, but yet we can listen to and have a conversation with somebody at the other side of the room. This is possible, since we select that particular voice and direct our attention to it. However, if the physical differences between the different voices were eliminated, we would not be able to single out one particular voice and pay attention to that. There are numerous psychological experiments that show that if we eliminate the physical differences between, different stimuli, we can no longer tell them apart. At the cocktail party we would not be able to listen to and talk to the person at the other side of the room. The differences in tone, cadence, loudness, etc, are a prerequisite for our ability to single out a particular voice from other voices.
Some processes are automatic, i.e. we do not need to be aware of the stimuli in order to perceive it. On the other hand, if we come across new situations or events, or when we are learning something new, we have to pay conscious attention to what we are doing. Such processes cannot be automatic. Driving a car and reading are two examples that illustrate the difference between automatic and conscious processes. Reading is automatic, it takes no conscious effort to read. We read letters, syllables, words and sentences without being aware of the reading process and without having to direct our attention to it. Learning to read is an entirely different matter that takes a lot of conscious effort. You have to look closely at each separate letter. You have to learn the syllables and the words and you must pay attention to every little detail in the text. Driving a car is also automatic, once you know how to do it. You do not have to direct conscious attention at what you are doing, e.g. changing gears or looking in the rear-view mirror. The relevant stimuli are selected and processed automatically as part of the decision making process. But, while learning how to drive, we have to consciously direct our attention at the relevant stimuli.
Constructivism holds that the perception process is an active process that creates a model of the world by combining information input from the outside world with stored knowledge. The Gestalt Laws provide an example of the constructivist approach. The Gestalt Laws describe a set of principles that we use to process and group visual information input in meaningful ways. The principles are: proximity, similarity, closure, good continuation and symmetry. This means that the information presented in a user interface should be grouped or not grouped in accordance with these principles depending on how we want the user to perceive the information (as belonging to the same category or to different categories). The same applies to constructivist theories in general, i.e. that the user interface design must take into account the knowledge structures stored in the human cognitive system.
According to the ecological perception theory, we pick up information from the surrounding world and understand it without any further processing. The perception process is immediate but also active. We pick up the information in the outside world by means of active exploration of it. The perceptual information, affordance, is present in the objects in the outside world. Inter-modality provides an example of affordance. We can, for instance, "see" or "hear" softness. Softness is a characteristic in an object, and it is brought forth or "radiated" as an affordance. We can perceive the softness affordance, irrespective of the modality we use to perceive it - vision, hearing, touch, etc. Thus, ecological theory proposes that the surrounding world and the objects in it hold the characteristics that we can perceive immediately and without any intermediate processing steps.
This means that user interfaces must be designed so that the appropriate affordances of different interface objects are immediately obvious to the users. Door handles, for instance, may "radiate" a "push" or "pull" affordance, i.e. a flat surface that invites you to push the door away from you or a handle that invites you to pull the door towards you.
The above provides a brief introduction to perception and some theories of perception. In order to complete the picture you should read the literature and visit the links listed below.
The Gestalt Laws: