A contiguity is a series of things in contact or in proximity, or the state of being such a mass or series.
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Biology
A cluster of genes which are close to one another at a chromosome locus are called contiguous. Contiguous gene disorders result from deletions or duplications of a chromosome segment that cause a contiguous gene imbalance. Also, Contiguity refers to the way Taxonomy is ordered and formed after Charles Darwin wrote Theory of the Origins of Species in 1859. Before then, scientists used a more strict taxonomy based upon an organism's locomotion and mobility. Now science bases taxonomy on contiguity, tracking changes in an organism's anatomy over eons to show contiguous shaping over time.
Computer science
Memory elements are contiguous if adjacent and apparently connected (but they may, in fact, be disconnected). A computer file or other data stored on a mass storage system, particularly hard disk-based, is said to be contiguous—sometimes, ungrammatically, to be composed of one fragment—if the file data is in one continuous region without intervening extraneous data. A non-contiguous file is said to be fragmented, and can usually be defragmented with a software utility.
Geography
Political or geographical land divisions that, as a group, are not interrupted by other land or water are contiguous. In the United States, for example, the "48 contiguous states" excludes Hawaii and Alaska, which do not share borders with other U.S. states.
Other examples of geographical contiguity might include the "contiguous European Union" excluding member states such as the United Kingdom, Ireland, Sweden, Finland and Cyprus (these being non-contiguous), or the "contiguous United Kingdom" referring to all parts of the country excepting Northern Ireland (it being geographically non-contiguous).
Two or more contiguous municipalities can be consolidated into one, or one municipality can consist of many noncontiguous elements. For example, the Financially Distressed Municipalities Act allows the commonwealth of Pennsylvania to merge contiguous municipalities to reduce financial distress.
Geographic contiguity is important in biology, especially animal ranges. For a particular species, its habitat may be a 'contiguous range', or it might be broken, requiring periodic, typically seasonal migrations; (see: Disjunct distribution). The same concept of contiguous range is true for human transportation studies in an attempt to understand census geography. It also comes into play with electoral geography and politics.
Interaction design
Contiguous data is recognized by the fact that it must be in a particular order to keep its meaning. If you scramble letters or words in a text, meaning is lost.
Mathematics
The ideas of closeness are inherent in the concept of a contiguity space or proximity space. See also Law of Continuity. In addition, the Law of Continuity can be applied to conceptual computational abstract ideas.
Philosophy
Philosophers speak of contiguity when they assume two events or objects lying directly side by side in space and time without being connected by causality or any other principle.
Physics
Contiguity is a metallurgical property used to characterize microstructure of materials. It is computed by finding the ratio of solid–solid length to the sum of solid–solid and solid–liquid length of the microstructure.
Probability theory
The contiguity of a pair of sequences of probability measures is a property that relates to the commonality of the sets that have zero measure as the index in the sequence increases. See Contiguity (probability theory).
Psychology
Association by contiguity is the principle that ideas, memories, and experiences are linked when one is frequently experienced with the other. For example, if you constantly see a knife and a fork together they become linked (associated). The more these two items (stimuli) are perceived together the stronger the link between them. When one of the memories becomes activated later on, the linked (contiguously associated) memory becomes temporarily more activated and thus easier to be called into working memory. This process is called priming, and the initial memory that primed the other is called the retrieval cue.
Association by contiguity is the root of association by similarity. Association by similarity is the idea that one memory primes another through their common property or properties. Thus, an apple may prime a memory of a rose through the common property of red. These two become associated even though you may have never experienced an apple and a rose together (consistent with association by contiguity).
In the study of human memory, the contiguity effect has been found in studies of free recall. Analyses of free recall data indicates that there tends to be the greatest number of +/- 1 transitions between words, suggesting that a person is more likely to recall words together that are closer together in a list. This is shown in a graph of conditional response probability as a function of lag as originated by Dr. Michael Kahana. The probability of recall (y-axis) is plotted against the lag, or separation between subsequently recalled words. For example, if two items A and B are learned together, when cued with B, A is retrieved and vice versa due to their temporal contiguity, although there will be a stronger forward association (when cued with A, B is recalled).
The contiguity effect appears relatively constant, and has been predicted to have long-term effects according to the temporal context model proposed by Howard and Kahana. This model explains the contiguity effect in the following manner: when an item is presented, it activates the temporal context that was active when the item was originally studied. Since contexts of neighboring items overlap, and that overlap increases with decreasing lag between items, a contiguity effect results. The contiguity effect has even been found between items in different lists, although it has been speculated that these items could simply be intrusions.
When one associated memory, a group of associated memories, or a whole line of associated memories becomes primed, this is known as spreading activation.
In conditioning, contiguity refers to how associated a reinforcer is with behaviour. The higher the contiguity between events the greater the strength of the behavioural relationship.
Edwin Ray Guthrie's contiguity theory deals with patterned movements.