Heuristic

# Heuristic

Overview
Heuristic refers to experience-based techniques for problem solving, learning, and discovery. Heuristic methods are used to speed up the process of finding a satisfactory solution, where an exhaustive search is impractical. Examples of this method include using a "rule of thumb
Rule of thumb
A rule of thumb is a principle with broad application that is not intended to be strictly accurate or reliable for every situation. It is an easily learned and easily applied procedure for approximately calculating or recalling some value, or for making some determination...

", an educated guess, an intuitive judgment, or common sense
Common sense
Common sense is defined by Merriam-Webster as, "sound and prudent judgment based on a simple perception of the situation or facts." Thus, "common sense" equates to the knowledge and experience which most people already have, or which the person using the term believes that they do or should have...

.
Discussion
 Ask a question about 'Heuristic' Start a new discussion about 'Heuristic' Answer questions from other users Full Discussion Forum

Encyclopedia
Heuristic refers to experience-based techniques for problem solving, learning, and discovery. Heuristic methods are used to speed up the process of finding a satisfactory solution, where an exhaustive search is impractical. Examples of this method include using a "rule of thumb
Rule of thumb
A rule of thumb is a principle with broad application that is not intended to be strictly accurate or reliable for every situation. It is an easily learned and easily applied procedure for approximately calculating or recalling some value, or for making some determination...

", an educated guess, an intuitive judgment, or common sense
Common sense
Common sense is defined by Merriam-Webster as, "sound and prudent judgment based on a simple perception of the situation or facts." Thus, "common sense" equates to the knowledge and experience which most people already have, or which the person using the term believes that they do or should have...

.

In more precise terms, heuristics are strategies using readily accessible, though loosely applicable, information to control problem solving
Problem solving
Problem solving is a mental process and is part of the larger problem process that includes problem finding and problem shaping. Consideredthe most complex of all intellectual functions, problem solving has been defined as higher-order cognitive process that requires the modulation and control of...

in human beings and machines.

## Example

The most fundamental heuristic is trial and error
Trial and error
Trial and error, or trial by error, is a general method of problem solving, fixing things, or for obtaining knowledge."Learning doesn't happen from failure itself but rather from analyzing the failure, making a change, and then trying again."...

, which can be used in everything from matching nuts and bolts
Nut (hardware)
A nut is a type of hardware fastener with a threaded hole. Nuts are almost always used opposite a mating bolt to fasten a stack of parts together. The two partners are kept together by a combination of their threads' friction, a slight stretch of the bolt, and compression of the parts...

to finding the values of variables in algebra problems.

Here are a few other commonly used heuristics, from George Pólya
George Pólya
George Pólya was a Hungarian mathematician. He was a professor of mathematics from 1914 to 1940 at ETH Zürich and from 1940 to 1953 at Stanford University. He made fundamental contributions to combinatorics, number theory, numerical analysis and probability theory...

's 1945 book, How to Solve It
How to Solve It
How to Solve It is a small volume by mathematician George Pólya describing methods of problem solving.- Four principles :How to Solve It suggests the following steps when solving a mathematical problem:...

:

## Psychology

In psychology
Psychology
Psychology is the study of the mind and behavior. Its immediate goal is to understand individuals and groups by both establishing general principles and researching specific cases. For many, the ultimate goal of psychology is to benefit society...

, heuristics are simple, efficient rules, hard-coded by evolutionary processes or learned, which have been proposed to explain how people make decisions, come to judgments, and solve problems, typically when facing complex problems or incomplete information. These rules work well under most circumstances, but in certain cases lead to systematic errors or cognitive bias
Cognitive bias
A cognitive bias is a pattern of deviation in judgment that occurs in particular situations. Implicit in the concept of a "pattern of deviation" is a standard of comparison; this may be the judgment of people outside those particular situations, or may be a set of independently verifiable...

es.

Although much of the work of discovering heuristics in human decision-makers was done by Amos Tversky
Amos Tversky
Amos Nathan Tversky, was a cognitive and mathematical psychologist, a pioneer of cognitive science, a longtime collaborator of Daniel Kahneman, and a key figure in the discovery of systematic human cognitive bias and handling of risk. Much of his early work concerned the foundations of measurement...

and Daniel Kahneman
Daniel Kahneman
Daniel Kahneman is an Israeli-American psychologist and Nobel laureate. He is notable for his work on the psychology of judgment and decision-making, behavioral economics and hedonic psychology....

, the concept was originally introduced by Nobel laureate Herbert Simon
Herbert Simon
Herbert Alexander Simon was an American political scientist, economist, sociologist, and psychologist, and professor—most notably at Carnegie Mellon University—whose research ranged across the fields of cognitive psychology, cognitive science, computer science, public administration, economics,...

. Gerd Gigerenzer
Gerd Gigerenzer
Gerd Gigerenzer is a German psychologist who has studied the use of bounded rationality and heuristics in decision making, especially in medicine...

focuses on how heuristics can be used to make judgments that are in principle accurate, rather than producing cognitive biases – heuristics that are "fast and frugal".

In 2002, Daniel Kahneman and Shane Frederick
Shane Frederick
Shane Frederick is an associate professor at Yale University's School of Management. He earlier worked at Massachusetts Institute of Technology. He is the creator of the "Cognitive Reflection Test", or CRT, a form of intelligence test that tests how "rational" testees are...

proposed that cognitive heuristics work by a process called attribute substitution
Attribute substitution
Attribute substitution is a psychological process thought to underlie a number of cognitive biases and perceptual illusions. It occurs when an individual has to make a judgment that is computationally complex, and instead substitutes a more easily calculated heuristic attribute...

which happens without conscious awareness. According to this theory, when somebody makes a judgment (of a target attribute) which is computationally complex, a rather easier calculated heuristic attribute is substituted. In effect, a cognitively difficult problem is dealt with by answering a rather simpler problem, without being aware of this happening. This theory explains cases where judgments fail to show regression toward the mean
Regression toward the mean
In statistics, regression toward the mean is the phenomenon that if a variable is extreme on its first measurement, it will tend to be closer to the average on a second measurement, and—a fact that may superficially seem paradoxical—if it is extreme on a second measurement, will tend...

. Heuristics can be considered to reduce the complexity of clinical judgements in healthcare.

#### Well known

• Anchoring and adjustment
• Availability heuristic
Availability heuristic
The availability heuristic is a phenomenon in which people predict the frequency of an event, or a proportion within a population, based on how easily an example can be brought to mind....

• Representativeness heuristic
Representativeness heuristic
The representativeness heuristic is a psychological term describing a phenomenon wherein people judge the probability or frequency of a hypothesis by considering how much the hypothesis resembles available data as opposed to using a Bayesian calculation. While often very useful in everyday life, it...

• Naïve diversification
Naive diversification
Naïve diversification is a choice heuristic . Its first demonstration was made by Itamar Simonson in marketing in the context of consumption decisions by individuals. It was subsequently shown in the context of economic and financial decisions. Simonson showed that when people have to make...

• Escalation of commitment
Escalation of commitment
Escalation of commitment was first described by Barry M. Staw in his 1976 paper, "Knee deep in the big muddy: A study of escalating commitment to a chosen course of action"...

#### Less well known

• Affect heuristic
Affect heuristic
The affect heuristic is a heuristic in which current affect influences decisions. Simply put, it is a "rule of thumb" instead of a deliberative decision...

• Contagion heuristic
Contagion heuristic
The contagion heuristic is a psychological heuristic leading people to avoid contact with people or objects viewed as "contaminated" by previous contact with someone or something viewed as bad—or, less often, to seek contact with objects that have been in contact with people or things considered good...

• Effort heuristic
Effort heuristic
In psychology, an effort heuristic is a rule of thumb in which the value of an object is assigned based on the amount of perceived effort that went into producing the object. An example of this would be the comparison of \$100 earned, and \$100 found...

• Familiarity heuristic
Familiarity heuristic
In psychology, a mental heuristic is a rule of thumb in which current behavior is judged to be correct based on how similar it is to past behavior and its outcomes. Individuals assume that the circumstances underlying the past behavior still hold true for the present situation and that the past...

• Fluency heuristic
Fluency heuristic
A fluency heuristic in psychology is a mental heuristic where, if one out of two objects is processed more fluently, faster, or more smoothly, the mind infers that this object has the higher value with respect to what question is being considered. . See processing fluency...

• Gaze heuristic
Gaze heuristic
The gaze heuristic is a heuristic employed by people when trying to catch a ball. Experimental studies have shown that people do not act as though they were solving a system of differential equations that describe the forces acting on the ball while it is in the air and then run to the place at...

• Peak-end rule
Peak-end rule
According to the peak-end rule, we judge our past experiences almost entirely on how they were at their peak and how they ended. Other information is not lost, but it is not used. This includes net pleasantness or unpleasantness and how long the experience lasted.In one experiment, one group of...

• Recognition heuristic
Recognition heuristic
The recognition heuristic has been used as a model in the psychology of judgment and decision making and as a heuristic in artificial intelligence. It states: :...

• Scarcity heuristic
Scarcity heuristic
In human psychology, the scarcity heuristic is a mental heuristic in which the mind values something based on how easily it may lose it, especially to competitors....

• Similarity heuristic
Similarity heuristic
The similarity heuristic is a lesser-known psychological heuristic pertaining to how people make judgments based on similarity. More specifically, the similarity heuristic is used to account for how people make judgments based on the similarity between current situations and other situations or...

• Simulation heuristic
Simulation heuristic
The simulation heuristic is a psychological heuristic, or simplified mental strategy, according to which people determine the likelihood of an event based on how easy it is to picture the event mentally. Partially as a result, people regret more missing outcomes that had been easier to imagine,...

• Social proof
Social proof
Social proof, also known as informational social influence, is a psychological phenomenon where people assume the actions of others reflect correct behavior for a given situation...

• Take-the-best heuristic
Take-the-best heuristic
According to the take-the-best heuristic, when making a judgment based on multiple criteria, the criteria are tried one at a time according to their cue validity, and a decision is made based on the first criterion which discriminates between the alternatives....

## Philosophy

In philosophy
Philosophy
Philosophy is the study of general and fundamental problems, such as those connected with existence, knowledge, values, reason, mind, and language. Philosophy is distinguished from other ways of addressing such problems by its critical, generally systematic approach and its reliance on rational...

, especially in Continental European philosophy, the adjective
In grammar, an adjective is a 'describing' word; the main syntactic role of which is to qualify a noun or noun phrase, giving more information about the object signified....

"heuristic" (or the designation "heuristic device") is used when an entity X exists to enable understanding of, or knowledge concerning, some other entity Y. A good example is a model
Model (physical)
A physical model is a smaller or larger physical copy of an object...

which, as it is never identical with what it models, is a heuristic device to enable understanding of what it models. Stories, metaphors, etc., can also be termed heuristic in that sense. A classic example is the notion of utopia
Utopia
Utopia is an ideal community or society possessing a perfect socio-politico-legal system. The word was imported from Greek by Sir Thomas More for his 1516 book Utopia, describing a fictional island in the Atlantic Ocean. The term has been used to describe both intentional communities that attempt...

as described in Plato
Plato
Plato , was a Classical Greek philosopher, mathematician, student of Socrates, writer of philosophical dialogues, and founder of the Academy in Athens, the first institution of higher learning in the Western world. Along with his mentor, Socrates, and his student, Aristotle, Plato helped to lay the...

's best-known work, The Republic. This means that the "ideal city" as depicted in The Republic is not given as something to be pursued, or to present an orientation-point for development; rather, it shows how things would have to be connected, and how one thing would lead to another (often with highly problematic results), if one would opt for certain principles and carry them through rigorously.

"Heuristic" is also often commonly used as a noun
Noun
In linguistics, a noun is a member of a large, open lexical category whose members can occur as the main word in the subject of a clause, the object of a verb, or the object of a preposition .Lexical categories are defined in terms of how their members combine with other kinds of...

to describe a rule-of-thumb, procedure, or method. Philosophers of science have emphasized the importance of heuristics in creative thought and constructing scientific theories. (See The Logic of Scientific Discovery
The Logic of Scientific Discovery
The Logic of Scientific Discovery is a 1934 book by Karl Popper. It was originally written in German and titled Logik der Forschung. Then Popper reformulated his book in English and republished it in 1959. This forms the rare case of a major work to appear in two languages, both written and one...

, and philosophers such as Imre Lakatos
Imre Lakatos
Imre Lakatos was a Hungarian philosopher of mathematics and science, known for his thesis of the fallibility of mathematics and its 'methodology of proofs and refutations' in its pre-axiomatic stages of development, and also for introducing the concept of the 'research programme' in his...

, Lindley Darden
Lindley Darden
Lindley Darden is a contemporary philosopher of science, with a research focus on the philosophy of biology. She received her Ph.D. from the University of Chicago in 1974 and B.A. in 1968 from Rhodes College, and is currently Distinguished Scholar Teacher at the University of...

, William C. Wimsatt
William C. Wimsatt is a professor in the Department of Philosophy, the Committee on Conceptual and Historical Studies of Science , and the Committee on Evolutionary Biology at the University of Chicago...

, and others.)

## Law

In legal theory, especially in the theory of law and economics
Law and economics
The economic analysis of law is an analysis of law applying methods of economics. Economic concepts are used to explain the effects of laws, to assess which legal rules are economically efficient, and to predict which legal rules will be promulgated.-Relationship to other disciplines and...

, heuristics are used in the law
Law
Law is a system of rules and guidelines which are enforced through social institutions to govern behavior, wherever possible. It shapes politics, economics and society in numerous ways and serves as a social mediator of relations between people. Contract law regulates everything from buying a bus...

when case-by-case analysis would be impractical, insofar as "practicality" is defined by the interests of a governing body.

For instance, in all states in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

the legal drinking age
Legal drinking age
Laws about the legal drinking age cover a wide range of issues and behaviours, addressing when and where alcohol can be consumed. The minimum age alcohol can be legally consumed can be different to the age when it can be purchased. These laws vary among different countries and many laws have...

is 21, because it is argued that people need to be mature enough to make decisions involving the risks of alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....

consumption. However, assuming people mature at different rates, the specific age of 21 would be too late for some and too early for others. In this case, the somewhat arbitrary deadline is used because it is impossible or impractical to tell whether an individual is sufficiently mature for society to trust them with that kind of responsibility. Some proposed changes, however, have included the completion of an alcohol education course rather than the attainment of 21 years of age as the criterion for legal alcohol possession. This would put youth alcohol policy more on a case-by-case basis and less on a heuristic one, since the completion of such a course would presumably be voluntary and not uniform across the population.

The same reasoning applies to patent law. Patent
Patent
A patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....

s are justified on the grounds that inventors need to be protected in order to have incentive to invent. It is therefore argued that, in society's best interest, inventors should be issued a temporary government-granted monopoly
Monopoly
A monopoly exists when a specific person or enterprise is the only supplier of a particular commodity...

on their product, so that they can recoup their investment costs and make economic profit for a limited period. In the United States the length of this temporary monopoly is 20 years from the date the application for patent was filed, though the monopoly does not actually begin until the application has matured into a patent. However, like the drinking-age problem above, the specific length of time would need to be different for every product in order to be efficient; a 20-year term is used because it is difficult to tell what the number should be for any individual patent. More recently, some, including University of North Dakota
University of North Dakota
The University of North Dakota is a public university in Grand Forks, North Dakota, USA. Established by the Dakota Territorial Assembly in 1883, six years before the establishment of the state of North Dakota, UND is the oldest and largest university in the state and enrolls over 14,000 students. ...

law professor Eric E. Johnson, have argued that patents in different kinds of industries – such as software patent
Software patent
Software patent does not have a universally accepted definition. One definition suggested by the Foundation for a Free Information Infrastructure is that a software patent is a "patent on any performance of a computer realised by means of a computer program".In 2005, the European Patent Office...

s – should be protected for different lengths of time.

## Mass communication

In the study of media effects, judgmental heuristics have been shown to play an active role in the simplifying of news and political communication. Use of these cues and other signals from elites allow average people the opportunity to achieve a modest level of rationality in reaching a decision. This can be accomplished without having to devote any significant measure of cognitive effort normally required to arrive at thoughtful and considered choices. The limited capacity theory model and other information processing models have been influential in the study of how people encode, store and retrieve political information. Most people maintain a minimum level of interest in public affairs, and therefore employ simplifying shortcuts to arrive at political judgments. Common examples include referring to the complex military and intelligence activities by NATO forces in the Middle East simply as “the war on terror,” a reversal of a specific policy or position as a “flip-flop,” and the homogenization of any type of broad government assistance program as “socialism.”

Risk assessment of new technologies offers another example of how ordinary citizens seek shortcuts to expediently arrive at judgments. Most people maintain a low level of interest in issues that are not center to their daily lives, such as developments in the various fields of science and technology. Media frames can produce powerful heuristics that can have significant impact on public opinion about a given new technology. Research has shown media frames that suggest high risk often lead to strong negative perceptions and possible rejection of a technology. An example is the casting of genetically modified foods as “Frankenfoods” and using illustrations containing visual cues to Frankenstein’s monster.

## Computer science

In computer science
Computer science
Computer science or computing science is the study of the theoretical foundations of information and computation and of practical techniques for their implementation and application in computer systems...

, a heuristic is a technique designed to solve a problem that ignores whether the solution can be proven to be correct, but which usually produces a good solution or solves a simpler problem that contains or intersects with the solution of the more complex problem. Most real-time, and even some on-demand, anti-virus scanners
Antivirus software
Antivirus or anti-virus software is used to prevent, detect, and remove malware, including but not limited to computer viruses, computer worm, trojan horses, spyware and adware...

use heuristic signatures to look for specific attributes and characteristics for detecting viruses
Computer virus
A computer virus is a computer program that can replicate itself and spread from one computer to another. The term "virus" is also commonly but erroneously used to refer to other types of malware, including but not limited to adware and spyware programs that do not have the reproductive ability...

and other forms of malware
Malware
Malware, short for malicious software, consists of programming that is designed to disrupt or deny operation, gather information that leads to loss of privacy or exploitation, or gain unauthorized access to system resources, or that otherwise exhibits abusive behavior...

.

Heuristics are intended to gain computational performance or conceptual simplicity, potentially at the cost of accuracy or precision
Accuracy and precision
In the fields of science, engineering, industry and statistics, the accuracy of a measurement system is the degree of closeness of measurements of a quantity to that quantity's actual value. The precision of a measurement system, also called reproducibility or repeatability, is the degree to which...

.

In their Turing Award
Turing Award
The Turing Award, in full The ACM A.M. Turing Award, is an annual award given by the Association for Computing Machinery to "an individual selected for contributions of a technical nature made to the computing community. The contributions should be of lasting and major technical importance to the...

acceptance speech, Herbert Simon
Herbert Simon
Herbert Alexander Simon was an American political scientist, economist, sociologist, and psychologist, and professor—most notably at Carnegie Mellon University—whose research ranged across the fields of cognitive psychology, cognitive science, computer science, public administration, economics,...

and Allen Newell
Allen Newell
Allen Newell was a researcher in computer science and cognitive psychology at the RAND corporation and at Carnegie Mellon University’s School of Computer Science, Tepper School of Business, and Department of Psychology...

discuss the Heuristic Search Hypothesis: a physical symbol system will repeatedly generate and modify known symbol structures until the created structure matches the solution structure.

That is, each successive iteration depends upon the step before it, thus the heuristic search learns what avenues to pursue and which ones to disregard by measuring how close the current iteration is to the solution. Therefore, some possibilities will never be generated as they are measured to be less likely to complete the solution.

A heuristic method can accomplish its task by using search trees. However, instead of generating all possible solution branches, a heuristic selects branches more likely to produce outcomes than other branches. It is selective at each decision point, picking branches that are more likely to produce solutions.

In human-computer interaction, heuristic evaluation
Heuristic evaluation
A heuristic evaluation is a discount usability inspection method for computer software that helps to identify usability problems in the user interface design. It specifically involves evaluators examining the interface and judging its compliance with recognized usability principles...

is a usability-testing
Usability testing
Usability testing is a technique used in user-centered interaction design to evaluate a product by testing it on users. This can be seen as an irreplaceable usability practice, since it gives direct input on how real users use the system...

technique devised by expert usability consultants. In heuristic evaluation, the user interface
User interface
The user interface, in the industrial design field of human–machine interaction, is the space where interaction between humans and machines occurs. The goal of interaction between a human and a machine at the user interface is effective operation and control of the machine, and feedback from the...

is reviewed by experts and its compliance to usability heuristics (broadly stated characteristics of a good user interface, based on prior experience) is assessed, and any violating aspects are recorded.

## Software interface design

In software development, the use of a heuristic approach can facilitate a well-designed user interface
User interface
The user interface, in the industrial design field of human–machine interaction, is the space where interaction between humans and machines occurs. The goal of interaction between a human and a machine at the user interface is effective operation and control of the machine, and feedback from the...

, enabling users to navigate complex systems intuitively and without difficulty. The interface may guide the user when necessary using tooltips, help buttons, invitations to chat with support, etc., providing help when needed. However, in practice, the designer of the user interface may not find it easy to strike the optimum balance for assistance of the user.

Software developers and targeted end-users alike disregard heuristics at their own peril. End users often need to increase their understanding of the basic framework that a project entails (so that their expectations are realistic), and developers often need to push to learn more about their target audience (so that their learning styles can be judged). Business rules crucial to the organization are often so obvious to the end-user that they are not conveyed to the developer, who may lack domain knowledge
Domain knowledge
Domain knowledge is that valid knowledge used to refer to an area of human endeavour, an autonomous computer activity, or other specialized discipline.Specialists and experts use and develop their own domain knowledge...

in the particular field of endeavor the application is meant to serve.

A proper Software Requirements Specification
Software Requirements Specification
-Organization of an SRS:A Software Requirements Specification – a requirements specification for a software system – is a complete description of the behavior of a system to be developed. It includes a set of use cases that describe all the interactions the users will have with the software. In...

(SRS) models the heuristics of how a user will process the information being rendered on-screen. An SRS is ideally shared with the end-user well before the actual Software Design
Software design
Software design is a process of problem solving and planning for a software solution. After the purpose and specifications of software are determined, software developers will design or employ designers to develop a plan for a solution...

Specification (SDS) is written and the application is developed, so users' feedback about their experience can be used to adapt the design of the application. This saves much time in the Software Development Life Cycle (SDLC). Unless heuristics are adequately considered, the project will likely suffer many implementation problems and setbacks.

## Engineering

In engineering
Engineering
Engineering is the discipline, art, skill and profession of acquiring and applying scientific, mathematical, economic, social, and practical knowledge, in order to design and build structures, machines, devices, systems, materials and processes that safely realize improvements to the lives of...

, a heuristic is an experience-based method that can be used as an aid to solve process design problems, varying from size of equipment to operating conditions. By using heuristics, time can be reduced when solving problems. There are several methods which are available to engineers. These include Failure mode and effects analysis
Failure mode and effects analysis
A failure modes and effects analysis is a procedure in product development and operations management for analysis of potential failure modes within a system for classification by the severity and likelihood of the failures...

and Fault tree analysis
Fault tree analysis
Fault tree analysis is a top down, deductive failure analysis in which an undesired state of a system is analyzed using boolean logic to combine a series of lower-level events...

. The former relies on a group of qualified engineers to evaluate problems, rank them in order of importance and then recommend solutions. The methods of forensic engineering
Forensic engineering
Forensic engineering is the investigation of materials, products, structures or components that fail or do not operate or function as intended, causing personal injury or damage to property. The consequences of failure are dealt with by the law of product liability. The field also deals with...

are an important source of information for investigating problems, especially by elimination of unlikely causes and using the weakest link principle.

Because heuristics are fallible, it is important to understand their limitations. They are intended to be used as aids in order to make quick estimates and preliminary process designs.

## Pitfalls of heuristics

Heuristic algorithm
Algorithm
In mathematics and computer science, an algorithm is an effective method expressed as a finite list of well-defined instructions for calculating a function. Algorithms are used for calculation, data processing, and automated reasoning...

s are often employed because they may be seen to "work" without having been mathematically proven to meet a given set of requirements. One common pitfall in implementing a heuristic method to meet a requirement comes when the engineer or designer fails to realize that the current data set does not necessarily represent future system states.

While the existing data can be pored over and an algorithm can be devised to successfully handle the current data, it is imperative to ensure that the heuristic method employed is capable of handling future data sets. This means that the engineer or designer must fully understand the rules that generate the data and develop the algorithm to meet those requirements and not just address the current data sets.

Statistical analysis should be conducted when employing heuristics to estimate the probability of incorrect outcomes.

If one seeks to use a heuristic as a means of solving a search
Search problem
In computational complexity theory and computability theory, a search problem is a type of computational problem represented by a binary relation...

or knapsack
Knapsack problem
The knapsack problem or rucksack problem is a problem in combinatorial optimization: Given a set of items, each with a weight and a value, determine the count of each item to include in a collection so that the total weight is less than or equal to a given limit and the total value is as large as...

problem, then one must be careful to make sure that the heuristic function which one is choosing to use is an admissible heuristic
In computer science, specifically in algorithms related to Pathfinding, a heuristic function is said to be admissible if it is no more than the lowest-cost path to the goal. In other words, a heuristic is admissible if it never overestimates the cost of reaching the goal...

. Given a heuristic function labeled as:

which is meant to approximate the true optimal distance to the goal node in a directed graph containing total nodes or vertexes labeled .

"Admissible" means that for all where .

If a heuristic is not admissible, it might never find the goal, by ending up in a dead end of graph or by skipping back and forth between two nodes and where .

• Algorithm
Algorithm
In mathematics and computer science, an algorithm is an effective method expressed as a finite list of well-defined instructions for calculating a function. Algorithms are used for calculation, data processing, and automated reasoning...

• Behavioral economics
• Daniel Kahneman
Daniel Kahneman
Daniel Kahneman is an Israeli-American psychologist and Nobel laureate. He is notable for his work on the psychology of judgment and decision-making, behavioral economics and hedonic psychology....

• Failure mode and effects analysis
Failure mode and effects analysis
A failure modes and effects analysis is a procedure in product development and operations management for analysis of potential failure modes within a system for classification by the severity and likelihood of the failures...

• Problem solving
Problem solving
Problem solving is a mental process and is part of the larger problem process that includes problem finding and problem shaping. Consideredthe most complex of all intellectual functions, problem solving has been defined as higher-order cognitive process that requires the modulation and control of...

• Teachable moment
Teachable moment
A teachable moment, in education, is the time at which learning a particular topic or idea becomes possible or easiest.-In education:The concept was popularized by Robert Havighurst in his 1952 book, Human Development and Education. In the context of education theory, Havighurst explained,The...

• List of cognitive biases
• HAL 9000#Origin of name
• Bias
Bias
Bias is an inclination to present or hold a partial perspective at the expense of alternatives. Bias can come in many forms.-In judgement and decision making:...