Decision Making, Attention & Workload
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Features and Classes of Decision Making Decisions typically presents a many to one mapping- there is a lot of information, but only some is evaluated to make a decision. 4 major factors: 1. Uncertainty- should the pilot continue although the weather could be bad? 2. Familiarity and Expertise 3. Time, e.g. time pressure and stress 4. Classes of Decision making: 1. Rational and Normative Decision Making-e.g. to minimize loss 2. Naturalistic Decision Making
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What is good decision-making? It is no surprise that many errors happen in the decision making. It is however difficult to define good decision making. There are three characteristics of a good decision making: 1.
2.
3.
Expected value of a decision - this is the gold mark - the ‘normative school’ but difficult to agree on values. Should one minimize the maximum possible loss (buy another insurance ) or should one maximize long-term gain, or…? Different person thinks differently. Good decision produce good outcomes. But decisions produce bad outcomes – Example, the decision to launch Challenger. But in probabilistic world it is difficult to be predict what will happen. Concept of expertise. Some experts make good decisions (chess players physics experts) But experts do not necessarily do better than novices.
When all 3 characteristics converge, we probably have a good decision.
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Diagnosis and Situation Awareness in Decision Making. To make an effective choice he must understand the situation. Situation Awareness is one of the most important components in effective decision-making. We can distinguish four information processing components, • perception of the estimate cues, • attention for selecting and integrating information provided by the cues • the role of long-term memory in providing background knowledge to establish hypotheses • the role of the working memory as the work bench for updating and revising beliefs and hypotheses.
Given the iterative nature in how these interact this no single appropriate starting point –a Loop
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Situation Awareness “Situation awareness is the perception of the elements in an environment within a volume of time and space, the comprehension of their meaning, and the projection of their status in the near future.� Endsley (1995) - difficult to measure - different from regular information processing model. - Some people tend to have better Situation awareness because they are expert and they learned how to master the situation.
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Situation Awareness
The main features of situation awareness. Adapted from Endsley (1995)
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Evidence Accumulation: Cue Seeking and Hypothesis Formation Hypothesis Belief H1 H2
From Cues, many cues are presented. How should they be processed. First there must be attention. Second cue must be integrated.
(1) Diagnosticity (D)
0-1
H2 (2) Realiability [0-1] (R) (3) Physical features (salience) Cues
H1
H2
Info value [RxD]
H1
To visual Features with Salience. Salience is important for Attention To reliability or credibility assessment. Any eye witness to a crime makes a report, but he may lie? To Diagnosticity (and Info Value). Do dark clouds mean that it will be raining? To beliefs and Hypotheses. The medical doctor may think of a tumor as benign or malign.
Truth (True state of the world)
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Expectation in Diagnosis. The role of LTM LTM is important for 2 reasons: 1. Discover the correlations between cues that support RPD. 2. Discover frequent decisions Following are 2 Decision Heuristics (for discussion):
Representativeness People are supposed to diagnose a problem, chose a problem, choose a hypothesis and evaluate the cues to see if they match the hypothesis. A trouble shooter will hence observe a set of cues (light off, warning red, etc) and match them against a number of possibilities. If a match is made, a state is chosen. This is typical of RPD. For example a physician who observes 4 symptons out of 5, is likely to accept disease X- even though it may be a very uncommon disease. But physicians remain unaware of the disease rate when making the decision.
Availability Heuristic Availability refers to what is available in your mind- and the ease by which scenarios and modes of responding can surface in ones mind (Tversky and Kahneman, 1974). This heuristic could represent the probability of various decisions: People entertain several available hypotheses. An operator may have encountered a problem recently and decides that it is the same problem again. He may decide on a hypothesis that is easy to represent in memory- eg a single failure rather than a double failure will be chosen. People look for simple solutions- not complex.
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Recognition Primed Decision (RPD) The recognition-primed decision (RPD) model describes how people use their experience in the form of a repertoire of patterns (Klein, Calderwood, & ClintonCirocco, 1986). These patterns describe the primary causal factors operating in the situation. The patterns highlight the most relevant cues, provide expectancies, identify plausible goals, and suggest typical types of reactions in that type of situation.
If the correlation between cues is poor, then the decision maker should abandon the RPD style.
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Recognition Primed Decision (RPD) In RPD, there are 3 different decision situations: 1. The first situation where operators recognize a situation and act like they have acted before 2. Sometimes the situation may be a little different from past situations, and the operator will then go through a mental simulation of what could happen if he decide to act according to the familiar pattern. Only then may he decide to accept the common routine action. 3. An operator simulate the action again, but decides that a routine action no longer appropriate.
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Recognition Primed Decision (RPD) •In RPD, decision makers needs to make a decision they can quickly match the situation to the patterns they have learned. •find a clear match, they can carry out the most typical course of action. •make extremely rapid decisions, especially during a critical situation •make good decisions without comparing options. •use reliable heuristics and in most cases are correct, Klein (1989) •Has features of both Simon’s Satisficizing criteria (1969) and Rasmussen’s decision ladder
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Naturalistic Decision Making (NDM) Naturalistic decision making as defined in Wickens, Gordon & Liu (1998) is, “the way people use their experience to make decisions in field settings”. In the real world environment, tasks that involves decision making tend to have the following characteristics: •Ill structured problems. •Uncertain, Dynamic environment. •Information-rich environments where situational cues may change rapidly. •Cognitive processing that proceeds in iterative action/feedback loops. •Multiple shifting and/ or competing individual and organised goals. •Time constraints or time stress •High risk •Multiple persons somehow involved in the decision. (Wickens et al 1998. P.196-197).
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Rasmussen’s model This model describes 3 different levels of cognitive activity during task performance and decision making. 1. Skill Based Level: Skill based behavior is based on the sensory-motor performance and is operated without conscious control (or automated). Performance and decision making is at the subconscious level and is more of an automatic response to a particular situation. People who usually make skill based decisions are very experienced with the task at hand.
2. Rule Based Level: Rule based behavior is based on stored procedures (or induced by experience), it is also known as taught problem solving/planning. People will operate on this level when they are familiar enough with the task but do not have enough experience and will look for cues or rules that they may recognise from past experience to make a decision.
3. Knowledge Based Level: Knowledge based behavior occurs when user is in unfamiliar situations which requires explicit thinking. When the task at hand is novel and when people do not have any rules stored from past experiences, people will resort to analytical processing using conceptual information which involves problem definition, solution generation and determining the best course of action or planning before making a decision. (Wickens et al., 1998, p.198)
According to this model, a person may operate in one, two or even all three levels depending on the task and how experienced the person is. MA4847 Human Factor Engineering
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Rasmussen’s model
Rasmussen’s model of skill-based, and krule-based, nowledge-based behavior MA4847 Human Factor Engineering
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Norman’s Gulf of Execution and Evaluation This model is used extensively in Human Computer Interaction. Considerations when designing a system: • The system state and the alternatives are visible • There is a good conceptual model with a consistent system image • The interface has useful mapping that reveal relationship between stages • The user received continuous feedback on his action
Evaluation
The gulfs of evaluation and execution (Norman, 1988).
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Signal Detection Theory Signal Detection Theory is used to model certain types of events with information. E.g A radiologist examines an x-ray to determine if a tumor is malignant (signal) or benign (noise) Two stages of information processing are hypothesized 1. Accumulation of sensory evidence to judge the presence or absence of a signal 2. Decision if the accumulated evidence constitutes a signal or not.
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Signal Detection Theory
Signal-noise detection theory. There are two distribution curves of noise intensity and of signal intensity. The horizontal axis is the signal strength, and the operator will decide on a cut-off point at a location β. Values to the right represent a signal, and values to the left represent noise. The sensitivity d’ measures the distance between the two curves.
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Human Information Processing
Adapted from Wickens, C.D., Engineering Psychology and Human Performance, Harper Collins, New York, 1992.
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Attention • Attention is the process which the mind chooses from among the stimuli that strikes the senses at any given moment. • Allow only some information to enter into consciousness.
• Attention focus is voluntary or invoultary • Factors affecting attention focus include meaningfulness, structure of display, use of colour/intensity, use of modalities, etc.
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Types of Attention Focused attention: is commonly thought of as attentiveness. It is our ability to focus on one thing while excluding other things in our environment.
Sustained attention: This refers to the ability to maintain a consistence behavior response during continuous and repetitive activity.
Selective attention: This level of attention refers to the capacity to maintain a behavior al or cognitive set in the face of distracting or competing stimuli.
Divided attention: also known as multitasking, which is our ability to respond simultaneously to multiple tasks.
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Guidelines for Focused Attention •Make the competing channels as distinct as possible from the channel to which the person is to attend •Separate, in physical space, the competing channels from the channel of interest •Reduce the number of competing channels •Make the channel of interest larger, brighter, louder, or more centrally located than the competing channels.
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Guidelines for Sustained Attention •Provide appropriate work-rest schedules & task variation •Increase the conspicuousness of the signal and reduce the ambiguity of the signal •Have artificial signals & provide feedback on the performance with these artificial signals •Improve motivation •Provide training on the actual nature of signals •Maintain optimal environmental conditions
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Vigilance Level
Vigilance and Sustained Attention
Minutes
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Guidelines for Selective Attention •Use as few channels or sources of information as possible •Provide information on the relative importance of each channel •Reduce overall levels of stress •Provide a preview of where the information is likely to occur •Provide training for optimal scanning patterns •For visual channels reduce proximity to reduce scanning distance •For auditory channels avoid masking, i.e. avoid having two channels presenting information simultaneously. •For stimuli requiring responses separate temporally and present at a rate to allow for individual responses
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Guidelines for Divided Attention •Minimise the number of potential sources of information •provide information on the relative priorities of tasks to facilitate the optimal strategy for dividing attention •Make an effort to keep the difficulty levels of tasks as low as possible •Make tasks as dissimilar as possible in terms of input and output modalities and codes •Make learning on manual tasks as great as possible as they will have less of an effect on memory and sensory capabilities
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Multiple Resource Theory In the multiple resource theory individuals are viewed as having several different capacities of resources, these resources are differentiated according to information processing stages (encoding and central processing or responding), perceptual modality (auditory or visual) and processing codes (spatial or verbal). These multiple resources were represented by Wickens (1992) as follows:
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Multiple Resource Theory Wickens’ theory allows system designers to predict when: •Tasks can be performed concurrently. •Tasks will interfere with each other. •Increases in the difficulty of one task will result in a loss of performance of another task.
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Assessing Mental Workload In 1970, there was a landmark decision to reduce the crew size on medium-range jet aircraft by eliminating the flight engineers’ position. The Federal Aviation Administration required certification in terms of workload measures. •Workload measures are also of interest for: •Equipment design •Assess if resource demand exceeds supply •To identify performance bottleneck •Assessing operator performance •Identify training needs •Selection instrument to recruit operators
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Criteria for workload assessment Measures Workload assessment techniques vary along a number of dimension s, which may affect their validity and limit their use. 1. Sensitivity, Can the measure detect changes in the levels of workload imposed by a task? Identify a workload measure with the sensitivity required to meet the assessment objectives. 2. Diagnositicity. Can the measure be used to identify the factors of concern? 3. Selectivity. It is the techniques sensitive only to factors related to mental workload and information processing ability. 4. Obtrusiveness. Does the measure degrade primary task performance? Safety considerations can preclude the use of a technique that would degrade primary task performance. 5. Reliability. Does the measure provide repeatable values? 6. Implementability, Is the measure easy to implement?- Practical constraints dealing with measurement procedures and appratus and issues of operator training have to be considered. 7. Operator Acceptance. Is the operator willing to follow instructions and utilize a technique. Techniques perceived as intrusive or artificial could be ignored or performed at substandard levels. MA4847 Human Factor Engineering
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Subjective Measures Subject workload assessment techniques (SWAT)
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Subjective Measures NASA Task Load Index (TLX)
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End
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