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ACP Article SummaryWEEK 1
Lecture 2: Fundamentals
Information Processing (Chapter 5) - Wickens & Carswell - 2012 - Article
Introduction
In many situations, humans interact with systems. During these interactions, the operator
must perceive information and transform information into different forms. Sometimes these
transformations lead to errors. Understanding these transformations and thus understanding
information processing, is important for predicting and modeling human-system interactions.
Three approaches to information processing
There are three distinct approaches to information processing: the classic stage-based
approach; the ecological approach and cognitive engineering or ergonomics.
The classic stage-based approach
In this approach, the digital computer is used as a metaphor to human behaviour.
Information is seen as passing through a number of discrete stages. So, there is a distinction
between a perceptual stage and a stage of execution and action, which is based on the
morphological distinctions between perceptual and motor cortex. Proof for this approach
comes from the fact that different tasks and environmental factors have a different influence
on different stages. Within this approach, processing does not always start at stage 1:
sometimes processing starts when someone gives a response.
The ecological approach
This approach places more emphasis on the integrated flow of information through the
human rather than making a distinction between stages. It also emphasises the interaction
between humans and the environment. This approach is most relevant to describing human
behaviour in interaction with the natural environment, so it is used most when designing
controls and displays that mimic characteristics of the natural environment.
The cognitive engineering approach
This approach is a hybrid of the stage-based and ecological approach. On the one hand, it is
based on a very careful understanding of the environment and task constraints within which
an operator works. On the other hand, this approach places great emphasis on modelling
and understanding the knowledge structures that expert operators have of the domain.
,Selection information
Broadbent's book lead to that human information processing is now seen as part of a filtering
process. This filtering happens through mechanisms of human attention. Attention has three
different modes: selective attention, focused attention and divided attention.
Selective attention
Selective attention refers to how attention is focused on a particular object in the
environment for a certain period of time. It is influenced by four factors: salience, effort,
expectancy and value. So, selective attention dictates where attention is given to.
Focused attention
Focused attention is used to maintain processing of the desired sources and avoid the
distracting influence of potentially competing stimuli.
Divided attention
This is the ability to process more than one attribute or element of the environment at a
given time.
Visual search
When people are looking for something in a cluttered environment (for instance when they
are looking for a sign by the roadway), they use selective and focused attention as well as
discrimination. Visual search models are used to predict the time that is required to find a
target. These predictions can be very important for safety and productivity.
The most simple model of visual search is the serial self-terminating model. In this model, it
states that search space is filled with items of which most are non targets (so, distractors).
The mean time to find a target is modelled to be RT = NT/2. N is the number of items in the
space and T is the time that is needed to examine each item and determine that it is not a
target before moving on to the next. This model is influenced by three factors: bottom-up
parallel processing, top-down processing and target familiarity. Bottom-up processing is
about that for example all targets are 'highlighted', so that searching for these targets is
easier. Top-down processing is about how the operator's knowledge or expectations
influence the information processing. For example, location expectancy will create search
strategies that scan the most likely locations first. Another influence is the expectancy of
whether a target will be present or not. This is called the 'target prevalence rate'. A third
factor that influences visual search is target familiarity: this means that repeated exposures
to the same consistent target can speed the search for that target and reduce the likelihood
that the target may be missed.
,Perception and data interpretation
The Signal Detection Theory
When designing displays, it is very important that critical targets must be detectable in the
environment. However, assuring this detectability can be difficult. It is often the case that
changes in a scene are missed. However, sometimes it is also the case that people respond
as if they saw something, while there was no target. This is called a false alarm. The SDT
provides a framework for describing the processes that can lead to both types of errors.
Expectancy, context and identification
Prior knowledge can also influence the ability to identify enormous numbers of objects. For
example, it seems that objects and attributes are recognized more quickly when they are
embedded in consistent contexts, rather than when they are presented alone or in different,
inconsistent contexts. For example, words are more easily identified when they are
embedded in sentences, compared to when words are presented alone.
Judgments of Two-Dimensional Position and Extent
Spatial judgments that are required to read even everyday graphs, are prone to systematic
distortions. A few examples of these distortions are that people overestimate the values that
are represented in bar graphs; perceptual flattening of line graphs with respect to the y-axis,
which results in larger underestimations of the represented data as the reader follows the
line from its origin; cyclic patterns of bias in estimations of part-whole relationships that are
dependent on the number of available reference points on the graphs; distance distortions
between cursor locations and target/icon locations induced by the shape of the cursor.
Judgments of Distance and Size in Three-Dimensional Space
There are five kinds of cues that help during perception:
When making judgments in spaces, human perception depends on different cues that
provide information about the relative or absolute distance from the viewer. Many of these
cues are called pictorial cues, because they cues can be used to generate the impression of
depth in 2D pictures.
Next to pictorial cues, there are five cues that have to do with characteristics of the viewer:
Motion parallax: this refers to that objects moving at a constant speed across the frame will
appear to move an greater amount if they are closer to an observer than they would if they
were at a greater distance. Binocular disparity: this refers to the difference in viewpoint of the
two eyes. Stereopsis: this is the use of binocular disparity to perceive depth (think about 3D
displays). Accommodation and binocular convergence: these cues result from the natural
adjustment of the eyes that is needed to focus on specific objects at different distances.
, Comprehension and cognition
Working Memory limitations
There is a limited number of ideas, sounds and images that we can maintain and use in our
mind. For example, the items in the working memory are lost when they are not repeated.
This is called the memory span. Baddeley developed a four-part model of the working
memory, which includes two temporary storage systems: the phonological loop and
visuospatial sketchpad. These subsystems are used by a central executive, which
manipulates the information in these stores and creates multimodal representations of
coherent objects. These representations are then held in an episodic buffer.
Knowledge about the working memory has some implications for design:
Whenever possible, try to avoid codes that are too long for the memory capacity; when it is
necessary to use codes that exceed this limits, use methods such as parsing material into
lower units (chunking); because information from working memory is lost after a few
seconds, systems should be designed in such a way that they can use the information (think
about voice menu systems: in these cases, the users should be able to make a choice
immediately); the need to scan should be minimized if a person must hold spatial information
in the sketchpad; avoid the need to transfer information from one subsystem into the other
before further transformations or integrations can be made; if working memory subsystems
are updated too rapidly, old information may interfere with new; interference in working
memory is most likely when-to-be remember information is similar in either meaning or
sound; the capacity of working memory varies between people.
Planning and problem solving
In contrast with cognitive activities that are heavily driven by information about the
environment, the information-processing tasks of planning and problem solving are more
dependent on the interplay between information that is available in the long-term memory
and information-processing transformations carried out in working memory.
Schedule
Planning can depend on two types of cognitive operations: planners may depend on scripts
that they have stored in their long-term memory which are based on past experience;
planning may involve guess work and some level of mental stimulation of future activities.
Problem solving, diagnosis and troubleshooting
These three activities are related to each other: they all have in common that there is a goal
to be obtained by the human operator, that information to achieve that goal is currently
missing and that some physical action or mental operation must be taken to seek these
entities.
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