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=                           Communication                            =
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                             Introduction                             
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Communication is commonly defined as the transmission of information.
Its precise definition is disputed and there are disagreements about
whether unintentional or failed transmissions are included and whether
communication not only transmits meaning but also creates it. Models
of communication are simplified overviews of its main components and
their interactions. Many models include the idea that a source uses a
coding system to express information in the form of a message. The
message is sent through a channel to a receiver who has to decode it
to understand it. The main field of inquiry investigating
communication is called communication studies.

A common way to classify communication is by whether information is
exchanged between humans, members of other species, or non-living
entities such as computers. For human communication, a central
contrast is between verbal and non-verbal communication. Verbal
communication involves the exchange of messages in linguistic form,
including spoken and written messages as well as sign language.
Non-verbal communication happens without the use of a linguistic
system, for example, using body language, touch, and facial
expressions. Another distinction is between interpersonal
communication, which happens between distinct persons, and
intrapersonal communication, which is communication with oneself.
Communicative competence is the ability to communicate well and
applies to the skills of formulating messages and understanding them.

Non-human forms of communication include animal and plant
communication. Researchers in this field often refine their definition
of communicative behavior by including the criteria that observable
responses are present and that the participants benefit from the
exchange. Animal communication is used in areas like courtship and
mating, parent-offspring relations, navigation, and self-defense.
Communication through chemicals is particularly important for the
relatively immobile plants. For example, maple trees release so-called
volatile organic compounds into the air to warn other plants of a
herbivore attack. Most communication takes place between members of
the same species. The reason is that its purpose is usually some form
of cooperation, which is not as common between different species.
Interspecies communication happens mainly in cases of symbiotic
relationships. For instance, many flowers use symmetrical shapes and
distinctive colors to signal to insects where nectar is located.
Humans engage in interspecies communication when interacting with pets
and working animals.

Human communication has a long history and how people exchange
information has changed over time. These changes were usually
triggered by the development of new communication technologies.
Examples are the invention of writing systems, the development of mass
printing, the use of radio and television, and the invention of the
internet. The technological advances also led to new forms of
communication, such as the exchange of data between computers.


                             Definitions                              
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The word ' has its root in the Latin verb , which means  or .
Communication is usually understood as the transmission of
information: a message is conveyed from a sender to a receiver using
some medium, such as sound, written signs, bodily movements, or
electricity. Sender and receiver are often distinct individuals but it
is also possible for an individual to communicate with themselves. In
some cases, sender and receiver are not individuals but groups like
organizations, social classes, or nations. In a different sense, the
term 'communication' refers to the message that is being communicated
or to the field of inquiry studying communicational phenomena.

The precise characterization of communication is disputed. Many
scholars have raised doubts that any single definition can capture the
term accurately. These difficulties come from the fact that the term
is applied to diverse phenomena in different contexts, often with
slightly different meanings. The issue of the right definition affects
the research process on many levels. This includes issues like which
empirical phenomena are observed, how they are categorized, which
hypotheses and laws are formulated as well as how systematic theories
based on these steps are articulated.

Some definitions are broad and encompass unconscious and non-human
behavior. Under a broad definition, many animals communicate within
their own species and flowers communicate by signaling the location of
nectar to bees through their colors and shapes. Other definitions
restrict communication to conscious interactions among human beings.
Some approaches focus on the use of symbols and signs while others
stress the role of understanding, interaction, power, or transmission
of ideas. Various characterizations see the communicator's intent to
send a message as a central component. In this view, the transmission
of information is not sufficient for communication if it happens
unintentionally. A version of this view is given by philosopher Paul
Grice, who identifies communication with actions that aim to make the
recipient aware of the communicator's intention. One question in this
regard is whether only successful transmissions of information should
be regarded as communication. For example, distortion may interfere
with and change the actual message from what was originally intended.
A closely related problem is whether acts of deliberate deception
constitute communication.

According to a broad definition by literary critic I. A. Richards,
communication happens when one mind acts upon its environment to
transmit its own experience to another mind. Another interpretation is
given by communication theorists Claude Shannon and Warren Weaver, who
characterize communication as a transmission of information brought
about by the interaction of several components, such as a source, a
message, an encoder, a channel, a decoder, and a receiver. The
transmission view is rejected by transactional and constitutive views,
which hold that communication is not just about the transmission of
information but also about the creation of meaning. Transactional and
constitutive perspectives hold that communication shapes the
participant's experience by conceptualizing the world and making sense
of their environment and themselves. Researchers studying animal and
plant communication focus less on meaning-making. Instead, they often
define communicative behavior as having other features, such as
playing a beneficial role in survival and reproduction, or having an
observable response.


                       Models of communication                        
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Models of communication are conceptual representations of the process
of communication. Their goal is to provide a simplified overview of
its main components. This makes it easier for researchers to formulate
hypotheses, apply communication-related concepts to real-world cases,
and test predictions. Due to their simplified presentation, they may
lack the conceptual complexity needed for a comprehensive
understanding of all the essential aspects of communication. They are
usually presented visually in the form of diagrams showing the basic
components and their interaction.

Models of communication are often categorized based on their intended
applications and how they conceptualize communication. Some models are
general in the sense that they are intended for all forms of
communication. Specialized models aim to describe specific forms, such
as models of mass communication.

One influential way to classify communication is to distinguish
between linear transmission, interaction, and transaction models.
Linear transmission models focus on how a sender transmits information
to a receiver. They are 'linear' because this flow of information only
goes in a single direction. This view is rejected by interaction
models, which include a feedback loop. Feedback is needed to describe
many forms of communication, such as a conversation, where the
listener may respond to a speaker by expressing their opinion or by
asking for clarification. Interaction models represent the process as
a form of two-way communication in which the communicators take turns
sending and receiving messages. Transaction models further refine this
picture by allowing representations of sending and responding at the
same time. This modification is needed to describe how the listener
can give feedback in a face-to-face conversation while the other
person is talking. Examples are non-verbal feedback through body
posture and facial expression. Transaction models also hold that
meaning is produced during communication and does not exist
independently of it.

All the early models, developed in the middle of the 20th century, are
linear transmission models. Lasswell's model, for example, is based on
five fundamental questions: "Who?", "Says what?", "In which channel?",
"To whom?", and "With what effect?". The goal of these questions is to
identify the basic components involved in the communicative process:
the sender, the message, the channel, the receiver, and the effect.
Lasswell's model was initially only conceived as a model of mass
communication, but it has been applied to other fields as well. Some
communication theorists, like Richard Braddock, have expanded it by
including additional questions, like "Under what circumstances?" and
"For what purpose?".

The Shannon-Weaver model is another influential linear transmission
model. It is based on the idea that a source creates a message, which
is then translated into a signal by a transmitter. Noise may interfere
with and distort the signal. Once the signal reaches the receiver, it
is translated back into a message and made available to the
destination. For a landline telephone call, the person calling is the
source and their telephone is the transmitter. The transmitter
translates the message into an electrical signal that travels through
the wire, which acts as the channel. The person taking the call is the
destination and their telephone is the receiver. The Shannon-Weaver
model includes an in-depth discussion of how noise can distort the
signal and how successful communication can be achieved despite noise.
This can happen by making the message partially redundant so that
decoding is possible nonetheless. Other influential linear
transmission models include Gerbner's model and Berlo's model.

The earliest interaction model was developed by communication theorist
Wilbur Schramm. He states that communication starts when a source has
an idea and expresses it in the form of a message. This process is
called 'encoding' and happens using a code, i.e. a sign system that is
able to express the idea, for instance, through visual or auditory
signs. The message is sent to a destination, who has to decode and
interpret it to understand it. In response, they formulate their own
idea, encode it into a message, and send it back as a form of
feedback. Another innovation of Schramm's model is that previous
experience is necessary to be able to encode and decode messages. For
communication to be successful, the fields of experience of source and
destination have to overlap.

The first transactional model was proposed by communication theorist
Dean Barnlund in 1970. He understands communication as "the production
of meaning, rather than the production of messages". Its goal is to
decrease uncertainty and arrive at a shared understanding. This
happens in response to external and internal cues. Decoding is the
process of ascribing meaning to them and encoding consists in
producing new behavioral cues as a response.


                                Human                                 
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There are many forms of human communication. A central distinction is
whether language is used, as in the contrast between verbal and
non-verbal communication. A further distinction concerns whether one
communicates with others or with oneself, as in the contrast between
interpersonal and intrapersonal communication. Forms of human
communication are also categorized by their channel or the medium used
to transmit messages. The field studying human communication is known
as anthroposemiotics.


 Verbal 
========
Verbal communication is the exchange of messages in linguistic form,
i.e., by means of language. In colloquial usage, verbal communication
is sometimes restricted to oral communication and may exclude writing
and sign language. However, in academic discourse, the term is usually
used in a wider sense, encompassing any form of linguistic
communication, whether through speech, writing, or gestures. Some of
the challenges in distinguishing verbal from non-verbal communication
come from the difficulties in defining what exactly 'language' means.
Language is usually understood as a conventional system of symbols and
rules used for communication. Such systems are based on a set of
simple units of meaning that can be combined to express more complex
ideas. The rules for combining the units into compound expressions are
called grammar. Words are combined to form sentences.

One hallmark of human language, in contrast to animal communication,
lies in its complexity and expressive power. Human language can be
used to refer not just to concrete objects in the here-and-now but
also to spatially and temporally distant objects and to abstract
ideas. Humans have a natural tendency to acquire their native language
in childhood. They are also able to learn other languages later in
life as second languages. However, this process is less intuitive and
often does not result in the same level of linguistic competence. The
academic discipline studying language is called 'linguistics'. Its
subfields include semantics (the study of meaning), morphology (the
study of word formation), syntax (the study of sentence structure),
pragmatics (the study of language use), and phonetics (the study of
basic sounds).

A central contrast among languages is between natural and artificial
or constructed languages. Natural languages, like English, Spanish,
and Japanese, developed naturally and for the most part unplanned in
the course of history. Artificial languages, like Esperanto, Quenya,
C++, and the language of first-order logic, are purposefully designed
from the ground up. Most everyday verbal communication happens using
natural languages. Central forms of verbal communication are speech
and writing together with their counterparts of listening and reading.
Spoken languages use sounds to produce signs and transmit meaning
while for writing, the signs are physically inscribed on a surface.
Sign languages, like American Sign Language and Nicaraguan Sign
Language, are another form of verbal communication. They rely on
visual means, mostly by using gestures with hands and arms, to form
sentences and convey meaning.

Verbal communication serves various functions. One key function is to
exchange information, i.e. an attempt by the speaker to make the
audience aware of something, usually of an external event. But
language can also be used to express the speaker's feelings and
attitudes. A closely related role is to establish and maintain social
relations with other people. Verbal communication is also utilized to
coordinate one's behavior with others and influence them. In some
cases, language is not employed for an external purpose but only for
entertainment or personal enjoyment. Verbal communication further
helps individuals conceptualize the world around them and themselves.
This affects how perceptions of external events are interpreted, how
things are categorized, and how ideas are organized and related to
each other.


 Non-verbal 
============
Non-verbal communication is the exchange of information through
non-linguistic modes, like facial expressions, gestures, and postures.
However, not every form of non-verbal behavior constitutes non-verbal
communication. Some theorists, like Judee Burgoon, hold that it
depends on the existence of a socially shared coding system that is
used to interpret the meaning of non-verbal behavior. Non-verbal
communication has many functions. It frequently contains information
about emotions, attitudes, personality, interpersonal relations, and
private thoughts.

Non-verbal communication often happens unintentionally and
unconsciously, like sweating or blushing, but there are also conscious
intentional forms, like shaking hands or raising a thumb. It often
happens simultaneously with verbal communication and helps optimize
the exchange through emphasis and illustration or by adding additional
information. Non-verbal cues can clarify the intent behind a verbal
message. Using multiple modalities of communication in this way
usually makes communication more effective if the messages of each
modality are consistent. However, in some cases different modalities
can contain conflicting messages. For example, a person may verbally
agree with a statement but press their lips together, thereby
indicating disagreement non-verbally.

There are many forms of non-verbal communication. They include
kinesics, proxemics, haptics, paralanguage, chronemics, and physical
appearance. Kinesics studies the role of bodily behavior in conveying
information. It is commonly referred to as body language, even though
it is, strictly speaking, not a language but rather non-verbal
communication. It includes many forms, like gestures, postures,
walking styles, and dance. Facial expressions, like laughing, smiling,
and frowning, all belong to kinesics and are expressive and flexible
forms of communication. Oculesics is another subcategory of kinesics
in regard to the eyes. It covers questions like how eye contact, gaze,
blink rate, and pupil dilation form part of communication. Some
kinesic patterns are inborn and involuntary, like blinking, while
others are learned and voluntary, like giving a military salute.

Proxemics studies how personal space is used in communication. The
distance between the speakers reflects their degree of familiarity and
intimacy with each other as well as their social status. Haptics
examines how information is conveyed using touching behavior, like
handshakes, holding hands, kissing, or slapping. Meanings linked to
haptics include care, concern, anger, and violence. For instance,
handshaking is often seen as a symbol of equality and fairness, while
refusing to shake hands can indicate aggressiveness. Kissing is
another form often used to show affection and erotic closeness.

Paralanguage, also known as vocalics, encompasses non-verbal elements
in speech that convey information. Paralanguage is often used to
express the feelings and emotions that the speaker has but does not
explicitly stated in the verbal part of the message. It is not
concerned with the words used but with how they are expressed. This
includes elements like articulation, lip control, rhythm, intensity,
pitch, fluency, and loudness. For example, saying something loudly and
in a high pitch conveys a different meaning on the non-verbal level
than whispering the same words. Paralanguage is mainly concerned with
spoken language but also includes aspects of written language, like
the use of colors and fonts as well as spatial arrangement in
paragraphs and tables. Non-linguistic sounds may also convey
information; crying indicates that an infant is distressed, and
babbling conveys information about infant health and well-being.

Chronemics concerns the use of time, such as what messages are sent by
being on time versus late for a meeting. The physical appearance of
the communicator, such as height, weight, hair, skin color, gender,
clothing, tattooing, and piercing, also carries information.
Appearance is an important factor for first impressions but is more
limited as a mode of communication since it is less changeable. Some
forms of non-verbal communication happen using such artifacts as
drums, smoke, batons, traffic lights, and flags.

Non-verbal communication can also happen through visual media like
paintings and drawings. They can express what a person or an object
looks like and can also convey other ideas and emotions. In some
cases, this type of non-verbal communication is used in combination
with verbal communication, for example, when diagrams or maps employ
labels to include additional linguistic information.

Traditionally, most research focused on verbal communication. However,
this paradigm began to shift in the 1950s when research interest in
non-verbal communication increased and emphasized its influence. For
example, many judgments about the nature and behavior of other people
are based on non-verbal cues. It is further present in almost every
communicative act to some extent and certain parts of it are
universally understood. These considerations have prompted some
communication theorists, like Ray Birdwhistell, to claim that the
majority of ideas and information is conveyed this way. It has also
been suggested that human communication is at its core non-verbal and
that words can only acquire meaning because of non-verbal
communication. The earliest forms of human communication, such as
crying and babbling, are non-verbal. Some basic forms of communication
happen even before birth between mother and embryo and include
information about nutrition and emotions. Non-verbal communication is
studied in various fields besides communication studies, like
linguistics, semiotics, anthropology, and social psychology.


 Interpersonal 
===============
Interpersonal communication is communication between distinct people.
Its typical form is dyadic communication, i.e. between two people, but
it can also refer to communication within groups. It can be planned or
unplanned and occurs in many forms, like when greeting someone, during
salary negotiations, or when making a phone call. Some communication
theorists, like Virginia M. McDermott, understand interpersonal
communication as a fuzzy concept that manifests in degrees. In this
view, an exchange varies in how interpersonal it is based on several
factors. It depends on how many people are present, and whether it
happens face-to-face rather than through telephone or email. A further
factor concerns the relation between the communicators: group
communication and mass communication are less typical forms of
interpersonal communication and some theorists treat them as distinct
types.

Interpersonal communication can be synchronous or asynchronous. For
asynchronous communication, the parties take turns in sending and
receiving messages. This occurs when exchanging letters or emails. For
synchronous communication, both parties send messages at the same
time. This happens when one person is talking while the other person
sends non-verbal messages in response signaling whether they agree
with what is being said. Some communication theorists, like Sarah
Trenholm and Arthur Jensen, distinguish between content messages and
relational messages. Content messages express the speaker's feelings
toward the topic of discussion. Relational messages, on the other
hand, demonstrate the speaker's feelings toward their relation with
the other participants.

Various theories of the function of interpersonal communication have
been proposed. Some focus on how it helps people make sense of their
world and create society. Others hold that its primary purpose is to
understand why other people act the way they do and to adjust one's
behavior accordingly. A closely related approach is to focus on
information and see interpersonal communication as an attempt to
reduce uncertainty about others and external events. Other
explanations understand it in terms of the needs it satisfies. This
includes the needs of belonging somewhere, being included, being
liked, maintaining relationships, and influencing the behavior of
others. On a practical level, interpersonal communication is used to
coordinate one's actions with the actions of others to get things
done. Research on interpersonal communication includes topics like how
people build, maintain, and dissolve relationships through
communication. Other questions are why people choose one message
rather than another and what effects these messages have on the
communicators and their relation. A further topic is how to predict
whether two people would like each other.


 Intrapersonal 
===============
Intrapersonal communication is communication with oneself. In some
cases this manifests externally, like when engaged in a monologue,
taking notes, highlighting a passage, and writing a diary or a
shopping list. But many forms of intrapersonal communication happen
internally in the form of an inner exchange with oneself, like when
thinking about something or daydreaming. Closely related to
intrapersonal communication is communication that takes place within
an organism below the personal level, such as exchange of information
between organs or cells.

Intrapersonal communication can be triggered by internal and external
stimuli. It may happen in the form of articulating a phrase before
expressing it externally. Other forms are to make plans for the future
and to attempt to process emotions to calm oneself down in stressful
situations. It can help regulate one's own mental activity and outward
behavior as well as internalize cultural norms and ways of thinking.
External forms of intrapersonal communication can aid one's memory.
This happens, for example, when making a shopping list. Another use is
to unravel difficult problems, as when solving a complex mathematical
equation line by line. New knowledge can also be internalized this
way, like when repeating new vocabulary to oneself. Because of these
functions, intrapersonal communication can be understood as "an
exceptionally powerful and pervasive tool for thinking."

Based on its role in self-regulation, some theorists have suggested
that intrapersonal communication is more basic than interpersonal
communication. Young children sometimes use egocentric speech while
playing in an attempt to direct their own behavior. In this view,
interpersonal communication only develops later when the child moves
from their early egocentric perspective to a more social perspective.
A different explanation holds that interpersonal communication is more
basic since it is first used by parents to regulate what their child
does. Once the child has learned this, they can apply the same
technique to themselves to get more control over their own behavior.


 Channels 
==========
For communication to be successful, the message has to travel from the
sender to the receiver. The 'channel' is the way this is accomplished.
It is not concerned with the meaning of the message but only with the
technical means of how the meaning is conveyed. Channels are often
understood in terms of the senses used to perceive the message, i.e.
hearing, seeing, smelling, touching, and tasting. But in the widest
sense, channels encompass any form of transmission, including
technological means like books, cables, radio waves, telephones, or
television. Naturally transmitted messages usually fade rapidly
whereas some messages using artificial channels have a much longer
lifespan, as in the case of books or sculptures.

The physical characteristics of a channel have an impact on the code
and cues that can be used to express information. For example, typical
telephone calls are restricted to the use of verbal language and
paralanguage but exclude facial expressions. It is often possible to
translate messages from one code into another to make them available
to a different channel. An example is writing down a spoken message or
expressing it using sign language.

The transmission of information can occur through multiple channels at
once. For example, face-to-face communication often combines the
auditory channel to convey verbal information with the visual channel
to transmit non-verbal information using gestures and facial
expressions. Employing multiple channels can enhance the effectiveness
of communication by helping the receiver better understand the subject
matter. The choice of channels often matters since the receiver's
ability to understand may vary depending on the chosen channel. For
instance, a teacher may decide to present some information orally and
other information visually, depending on the content and the student's
preferred learning style. This underlines the role of a media-adequate
approach.


 Communicative competence 
==========================
Communicative competence is the ability to communicate effectively or
to choose the appropriate communicative behavior in a given situation.
It concerns what to say, when to say it, and how to say it. It further
includes the ability to receive and understand messages. Competence is
often contrasted with performance since competence can be present even
if it is not exercised, while performance consists in the realization
of this competence. However, some theorists reject a stark contrast
and hold that performance is the observable part and is used to infer
competence in relation to future performances.

Two central components of communicative competence are effectiveness
and appropriateness. Effectiveness is the degree to which the speaker
achieves their desired outcomes or the degree to which preferred
alternatives are realized. This means that whether a communicative
behavior is effective does not just depend on the actual outcome but
also on the speaker's intention, i.e. whether this outcome was what
they intended to achieve. Because of this, some theorists additionally
require that the speaker be able to give an explanation of why they
engaged in one behavior rather than another. Effectiveness is closely
related to efficiency, the difference being that effectiveness is
about achieving goals while efficiency is about using few resources
(such as time, effort, and money) in the process.

Appropriateness means that the communicative behavior meets social
standards and expectations. Communication theorist Brian H. Spitzberg
defines it as "the perceived legitimacy or acceptability of behavior
or enactments in a given context". This means that the speaker is
aware of the social and cultural context in order to adapt and express
the message in a way that is considered acceptable in the given
situation. For example, to bid farewell to their teacher, a student
may use the expression "Goodbye, sir" but not the expression "I gotta
split, man", which they may use when talking to a peer. To be both
effective and appropriate means to achieve one's preferred outcomes in
a way that follows social standards and expectations. Some definitions
of communicative competence put their main emphasis on either
effectiveness or appropriateness while others combine both features.

Many additional components of communicative competence have been
suggested, such as empathy, control, flexibility, sensitivity, and
knowledge. It is often discussed in terms of the individual skills
employed in the process, i.e. the specific behavioral components that
make up communicative competence. Message production skills include
reading and writing. They are correlated with the reception skills of
listening and reading. There are both verbal and non-verbal
communication skills. For example, verbal communication skills involve
the proper understanding of a language, including its phonology,
orthography, syntax, lexicon, and semantics.

Many aspects of human life depend on successful communication, from
ensuring basic necessities of survival to building and maintaining
relationships. Communicative competence is a key factor regarding
whether a person is able to reach their goals in social life, like
having a successful career and finding a suitable spouse. Because of
this, it can have a large impact on the individual's well-being. The
lack of communicative competence can cause problems both on the
individual and the societal level, including professional, academic,
and health problems.

Barriers to effective communication can distort the message. They may
result in failed communication and cause undesirable effects. This can
happen if the message is poorly expressed because it uses terms with
which the receiver is not familiar, or because it is not relevant to
the receiver's needs, or because it contains too little or too much
information. Distraction, selective perception, and lack of attention
to feedback may also be responsible. Noise is another negative factor.
It concerns influences that interfere with the message on its way to
the receiver and distort it. Crackling sounds during a telephone call
are one form of noise. Ambiguous expressions can also inhibit
effective communication and make it necessary to disambiguate between
possible interpretations to discern the sender's intention. These
interpretations depend also on the cultural background of the
participants. Significant cultural differences constitute an
additional obstacle and make it more likely that messages are
misinterpreted.


                            Other species                             
======================================================================
Besides human communication, there are many other forms of
communication found in the animal kingdom and among plants. They are
studied in fields like biocommunication and biosemiotics. There are
additional obstacles in this area for judging whether communication
has taken place between two individuals. Acoustic signals are often
easy to notice and analyze for scientists, but it is more difficult to
judge whether tactile or chemical changes should be understood as
communicative signals rather than as other biological processes.

For this reason, researchers often use slightly altered definitions of
communication to facilitate their work. A common assumption in this
regard comes from evolutionary biology and holds that communication
should somehow benefit the communicators in terms of natural
selection. The biologists Rumsaïs Blatrix and Veronika Mayer define
communication as "the exchange of information between individuals,
wherein both the signaller and receiver may expect to benefit from the
exchange". According to this view, the sender benefits by influencing
the receiver's behavior and the receiver benefits by responding to the
signal. These benefits should exist on average but not necessarily in
every single case. This way, deceptive signaling can also be
understood as a form of communication. One problem with the
evolutionary approach is that it is often difficult to assess the
impact of such behavior on natural selection. Another common pragmatic
constraint is to hold that it is necessary to observe a response by
the receiver following the signal when judging whether communication
has occurred.


 Animals 
=========
Animal communication is the process of giving and taking information
among animals. The field studying animal communication is called
zoosemiotics. There are many parallels to human communication. One is
that humans and many animals express sympathy by synchronizing their
movements and postures. Nonetheless, there are also significant
differences, like the fact that humans also engage in verbal
communication, which uses language, while animal communication is
restricted to non-verbal (i.e. non-linguistic) communication. Some
theorists have tried to distinguish human from animal communication
based on the claim that animal communication lacks a referential
function and is thus not able to refer to external phenomena. However,
various observations seem to contradict this view, such as the warning
signals in response to different types of predators used by vervet
monkeys, Gunnison's prairie dogs, and red squirrels. A further
approach is to draw the distinction based on the complexity of human
language, especially its almost limitless ability to combine basic
units of meaning into more complex meaning structures. One view states
that recursion sets human language apart from all non-human
communicative systems. Another difference is that human communication
is frequently linked to the conscious intention to send information,
which is often not discernable for animal communication. Despite these
differences, some theorists use the term "animal language" to refer to
certain communicative patterns in animal behavior that have
similarities with human language.

Animal communication can take a variety of forms, including visual,
auditory, tactile, olfactory, and gustatory communication. Visual
communication happens in the form of movements, gestures, facial
expressions, and colors. Examples are movements seen during mating
rituals, the colors of birds, and the rhythmic light of fireflies.
Auditory communication takes place through vocalizations by species
like birds, primates, and dogs. Auditory signals are frequently used
to alert and warn. Lower-order living systems often have simple
response patterns to auditory messages, reacting either by approach or
avoidance. More complex response patterns are observed for higher
animals, which may use different signals for different types of
predators and responses. For example, some primates use one set of
signals for airborne predators and another for land predators. Tactile
communication occurs through touch, vibration, stroking, rubbing, and
pressure. It is especially relevant for parent-young relations,
courtship, social greetings, and defense. Olfactory and gustatory
communication happen chemically through smells and tastes,
respectively.

There are large differences between species concerning what functions
communication plays, how much it is realized, and the behavior used to
communicate. Common functions include the fields of courtship and
mating, parent-offspring relations, social relations, navigation,
self-defense, and territoriality. One part of courtship and mating
consists in identifying and attracting potential mates. This can
happen through various means. Grasshoppers and crickets communicate
acoustically by using songs, moths rely on chemical means by releasing
pheromones, and fireflies send visual messages by flashing light. For
some species, the offspring depends on the parent for its survival.
One central function of parent-offspring communication is to recognize
each other. In some cases, the parents are also able to guide the
offspring's behavior.

Social animals, like chimpanzees, bonobos, wolves, and dogs, engage in
various forms of communication to express their feelings and build
relations. Communication can aid navigation by helping animals move
through their environment in a purposeful way, e.g. to locate food,
avoid enemies, and follow other animals. In bats, this happens through
echolocation, i.e. by sending auditory signals and processing the
information from the echoes. Bees are another often-discussed case in
this respect since they perform a type of dance to indicate to other
bees where flowers are located. In regard to self-defense,
communication is used to warn others and to assess whether a costly
fight can be avoided. Another function of communication is to mark and
claim territories used for food and mating. For example, some male
birds claim a hedge or part of a meadow by using songs to keep other
males away and attract females.

Two competing theories in the study of animal communication are nature
theory and nurture theory. Their conflict concerns to what extent
animal communication is programmed into the genes as a form of
adaptation rather than learned from previous experience as a form of
conditioning. To the degree that it is learned, it usually happens
through imprinting, i.e. as a form of learning that only occurs in a
certain phase and is then mostly irreversible.


 Plants, fungi, and bacteria 
=============================
Plant communication refers to plant processes involving the sending
and receiving of information. The field studying plant communication
is called phytosemiotics. This field poses additional difficulties for
researchers since plants are different from humans and other animals
in that they lack a central nervous system and have rigid cell walls.
These walls restrict movement and usually prevent plants from sending
and receiving signals that depend on rapid movement. However, there
are some similarities since plants face many of the same challenges as
animals. For example, they need to find resources, avoid predators and
pathogens, find mates, and ensure that their offspring survive. Many
of the evolutionary responses to these challenges are analogous to
those in animals but are implemented using different means. One
crucial difference is that chemical communication is much more
prominent in the plant kingdom in contrast to the importance of visual
and auditory communication for animals.

In plants, the term 'behavior' is usually not defined in terms of
physical movement, as is the case for animals, but as a biochemical
response to a stimulus. This response has to be short relative to the
plant's lifespan. Communication is a special form of behavior that
involves conveying information from a sender to a receiver. It is
distinguished from other types of behavior, like defensive reactions
and mere sensing. Like in the field of animal communication, plant
communication researchers often require as additional criteria that
there is some form of response in the receiver and that the
communicative behavior is beneficial to sender and receiver. Biologist
Richard Karban distinguishes three steps of plant communication: the
emission of a cue by a sender, the perception of the cue by a
receiver, and the receiver's response. For plant communication, it is
not relevant to what extent the emission of a cue is intentional.
However, it should be possible for the receiver to ignore the signal.
This criterion can be used to distinguish a response to a signal from
a defense mechanism against an unwanted change like intense heat.

Plant communication happens in various forms. It includes
communication within plants, i.e. within plant cells and between plant
cells, between plants of the same or related species, and between
plants and non-plant organisms, especially in the root zone. A
prominent form of communication is airborne and happens through
volatile organic compounds (VOCs). For example, maple trees release
VOCs when they are attacked by a herbivore to warn neighboring plants,
which then react accordingly by adjusting their defenses. Another form
of plant-to-plant communication happens through mycorrhizal fungi.
These fungi form underground networks, colloquially referred to as the
Wood-Wide Web, and connect the roots of different plants. The plants
use the network to send messages to each other, specifically to warn
other plants of a pest attack and to help prepare their defenses.

Communication can also be observed for fungi and bacteria. Some fungal
species communicate by releasing pheromones into the external
environment. For instance, they are used to promote sexual interaction
in several aquatic fungal species. One form of communication between
bacteria is called quorum sensing. It happens by releasing
hormone-like molecules, which other bacteria detect and respond to.
This process is used to monitor the environment for other bacteria and
to coordinate population-wide responses, for example, by sensing the
density of bacteria and regulating gene expression accordingly. Other
possible responses include the induction of bioluminescence and the
formation of biofilms.


 Interspecies 
==============
Most communication happens between members within a species as
intraspecies communication. This is because the purpose of
communication is usually some form of cooperation. Cooperation happens
mostly within a species while different species are often in conflict
with each other by competing over resources. However, there are also
some forms of interspecies communication. This occurs especially for
symbiotic relations and significantly less for parasitic or
predator-prey relations.

Interspecies communication plays a key role for plants that depend on
external agents for reproduction. For example, flowers need insects
for pollination and provide resources like nectar and other rewards in
return. They use communication to signal their benefits and attract
visitors by using distinctive colors and symmetrical shapes to stand
out from their surroundings. This form of advertisement is necessary
since flowers compete with each other for visitors. Many fruit-bearing
plants rely on plant-to-animal communication to disperse their seeds
and move them to a favorable location. This happens by providing
nutritious fruits to animals. The seeds are eaten together with the
fruit and are later excreted at a different location. Communication
makes animals aware of where the fruits are and whether they are ripe.
For many fruits, this happens through their color: they have an
inconspicuous green color until they ripen and take on a new color
that stands in visual contrast to the environment. Another example of
interspecies communication is found in the ant-plant relation. It
concerns, for instance, the selection of seeds by ants for their ant
gardens and the pruning of exogenous vegetation as well as plant
protection by ants.

Some animal species also engage in interspecies communication, like
apes, whales, dolphins, elephants, and dogs. For example, different
species of monkeys use common signals to cooperate when threatened by
a common predator. Humans engage in interspecies communication when
interacting with pets and working animals. For instance, acoustic
signals play a central role in communication with dogs. Dogs can learn
to react to various commands, like "sit" and "come". They can even be
trained to respond to short syntactic combinations, like "bring X" or
"put X in a box". They also react to the pitch and frequency of the
human voice to detect emotions, dominance, and uncertainty. Dogs use a
range of behavioral patterns to convey their emotions to humans, for
example, in regard to aggressiveness, fearfulness, and playfulness.


                               Computer                               
======================================================================
Computer communication concerns the exchange of data between computers
and similar devices. For this to be possible, the devices have to be
connected through a transmission system that forms a network between
them. A transmitter is needed to send messages and a receiver is
needed to receive them. A personal computer may use a modem as a
transmitter to send information to a server through the public
telephone network as the transmission system. The server may use a
modem as its receiver. To transmit the data, it has to be converted
into an electric signal. Communication channels used for transmission
are either analog or digital and are characterized by features like
bandwidth and latency.

There are many forms of computer networks. The most commonly discussed
ones are LANs and WANs. 'LAN' stands for 'local area network', which
is a computer network within a limited area, usually with a distance
of less than one kilometer. This is the case when connecting two
computers within a home or an office building. LANs can be set up
using a wired connection, like Ethernet, or a wireless connection,
like Wi-Fi. 'WANs', on the other hand, are 'wide area networks' that
span large geographical regions, like the internet. Their networks are
more complex and may use several intermediate connection nodes to
transfer information between endpoints. Further types of computer
networks include PANs (personal area networks), CANs (campus area
networks), and MANs (metropolitan area networks).

For computer communication to be successful, the involved devices have
to follow a common set of conventions governing their exchange. These
conventions are known as the communication protocol. They concern
various aspects of the exchange, like the format of messages and how
to respond to transmission errors. They also cover how the two systems
are synchronized, for example, how the receiver identifies the start
and end of a signal. Based on the flow of informations, systems are
categorized as simplex, half-duplex, and full-duplex. For simplex
systems, signals flow only in one direction from the sender to the
receiver, like in radio, cable television, and screens displaying
arrivals and departures at airports. Half-duplex systems allow two-way
exchanges but signals can only flow in one direction at a time, like
walkie-talkies and police radios. In the case of full-duplex systems,
signals can flow in both directions at the same time, like regular
telephone and internet. In either case, it is often important for
successful communication that the connection is secure to ensure that
the transmitted data reaches only the intended destination and is not
intercepted by an unauthorized third party. This can be achieved by
using cryptography, which changes the format of the transmitted
information to make it unintelligible to potential interceptors.

Human-computer communication is a closely related field that concerns
topics like how humans interact with computers and how data in the
form of inputs and outputs is exchanged. This happens through a user
interface, which includes the hardware used to interact with the
computer, like a mouse, a keyboard, and a monitor, as well as the
software used in the process. On the software side, most early user
interfaces were command-line interfaces in which the user must type a
command to interact with the computer. Most modern user interfaces are
graphical user interfaces, like Microsoft Windows and macOS, which are
usually much easier to use for non-experts. They involve graphical
elements through which the user can interact with the computer,
commonly using a design concept known as skeumorphism to make a new
concept feel familiar and speed up understanding by mimicking the
real-world equivalent of the interface object. Examples include the
typical computer folder icon and recycle bin used for discarding
files. One aim when designing user interfaces is to simplify the
interaction with computers. This helps make them more user-friendly
and accessible to a wider audience while also increasing productivity.


                        Communication studies                         
======================================================================
Communication studies, also referred to as 'communication science', is
the academic discipline studying communication. It is closely related
to semiotics, with one difference being that communication studies
focuses more on technical questions of how messages are sent,
received, and processed. Semiotics, on the other hand, tackles more
abstract questions in relation to meaning and how signs acquire it.
Communication studies covers a wide area overlapping with many other
disciplines, such as biology, anthropology, psychology, sociology,
linguistics, media studies, and journalism.

Many contributions in the field of communication studies focus on
developing models and theories of communication. Models of
communication aim to give a simplified overview of the main components
involved in communication. Theories of communication try to provide
conceptual frameworks to accurately present communication in all its
complexity. Some theories focus on communication as a practical art of
discourse while others explore the roles of signs, experience,
information processing, and the goal of building a social order
through coordinated interaction. Communication studies is also
interested in the functions and effects of communication. It covers
issues like how communication satisfies physiological and
psychological needs, helps build relationships, and assists in
gathering information about the environment, other individuals, and
oneself. A further topic concerns the question of how communication
systems change over time and how these changes correlate with other
societal changes. A related topic focuses on psychological principles
underlying those changes and the effects they have on how people
exchange ideas.

Communication was studied as early as Ancient Greece. Early
influential theories were created by Plato and Aristotle, who stressed
public speaking and the understanding of rhetoric. According to
Aristotle, for example, the goal of communication is to persuade the
audience. The field of communication studies only became a separate
research discipline in the 20th century, especially starting in the
1940s. The development of new communication technologies, such as
telephone, radio, newspapers, television, and the internet, has had a
big impact on communication and communication studies.

Today, communication studies is a wide discipline. Some works in it
try to provide a general characterization of communication in the
widest sense. Others attempt to give a precise analysis of one
specific form of communication. Communication studies includes many
subfields. Some focus on wide topics like interpersonal communication,
intrapersonal communication, verbal communication, and non-verbal
communication. Others investigate communication within a specific
area. Organizational communication concerns communication between
members of organizations such as corporations, nonprofits, or small
businesses. Central in this regard is the coordination of the behavior
of the different members as well as the interaction with customers and
the general public. Closely related terms are business communication,
corporate communication, and professional communication. The main
element of marketing communication is advertising but it also
encompasses other communication activities aimed at advancing the
organization's objective to its audiences, like public relations.
Political communication covers topics like electoral campaigns to
influence voters and legislative communication, like letters to a
congress or committee documents. Specific emphasis is often given to
propaganda and the role of mass media.

Intercultural communication is relevant to both organizational and
political communication since they often involve attempts to exchange
messages between communicators from different cultural backgrounds.
The cultural background affects how messages are formulated and
interpreted and can be the cause of misunderstandings. It is also
relevant for development communication, which is about the use of
communication for assisting in development, like aid given by
first-world countries to third-world countries. Health communication
concerns communication in the field of healthcare and health promotion
efforts. One of its topics is how healthcare providers, like doctors
and nurses, should communicate with their patients.


                               History                                
======================================================================
Communication history studies how communicative processes evolved and
interacted with society, culture, and technology. Human communication
has a long history and the way people communicate has changed
considerably over time. Many of these changes were triggered by the
development of new communication technologies and had various effects
on how people exchanged ideas. New communication technologies usually
require new skills that people need to learn to use them effectively.

In the academic literature, the history of communication is usually
divided into ages based on the dominant form of communication in that
age. The number of ages and the precise periodization are disputed.
They usually include ages for speaking, writing, and print as well as
electronic mass communication and the internet. According to
communication theorist Marshall Poe, the dominant media for each age
can be characterized in relation to several factors. They include the
amount of information a medium can store, how long it persists, how
much time it takes to transmit it, and how costly it is to use the
medium. Poe argues that subsequent ages usually involve some form of
improvement of one or more of the factors.

According to some scientific estimates, language developed around
40,000 years ago while others consider it to be much older. Before
this development, human communication resembled animal communication
and happened through a combination of grunts, cries, gestures, and
facial expressions. Language helped early humans to organize
themselves and plan ahead more efficiently. In early societies, spoken
language was the primary form of communication. Most knowledge was
passed on through it, often in the form of stories or wise sayings.
This form does not produce stable knowledge since it depends on
imperfect human memory. Because of this, many details differ from one
telling to the next and are presented differently by distinct
storytellers. As people started to settle and form agricultural
communities, societies grew and there was an increased need for stable
records of ownership of land and commercial transactions. This
triggered the invention of writing, which is able to solve many
problems that arose from using exclusively oral communication. It is
much more efficient at preserving knowledge and passing it on between
generations since it does not depend on human memory. Before the
invention of writing, certain forms of proto-writing had already
developed. Proto-writing encompasses long-lasting visible marks used
to store information, like decorations on pottery items, knots in a
cord to track goods, or seals to mark property.

Most early written communication happened through pictograms.
Pictograms are graphical symbols that convey meaning by visually
resembling real-world objects. The use of basic pictographic symbols
to represent things like farming produce was common in ancient
cultures and began around 9000 BCE. The first complex writing system
including pictograms was developed around 3500 BCE by the Sumerians
and is called cuneiform. Pictograms are still in use today, like
no-smoking signs and the symbols of male and female figures on
bathroom doors. A significant disadvantage of pictographic writing
systems is that they need a large amount of symbols to refer to all
the objects one wants to talk about. This problem was solved by the
development of other writing systems. For example, the symbols of
alphabetic writing systems do not stand for regular objects. Instead,
they relate to the sounds used in spoken language. Other types of
early writing systems include logographic and ideographic writing
systems. A drawback of many early forms of writing, like the clay
tablets used for cuneiform, was that they were not very portable. This
made it difficult to transport the texts from one location to another
to share information. This changed with the invention of papyrus by
the Egyptians around 2500 BCE and was further improved later by the
development of parchment and paper.

Until the 1400s, almost all written communication was hand-written,
which limited the spread of written media within society since copying
texts by hand was costly. The introduction and popularization of mass
printing in the middle of the 15th century by Johann Gutenberg
resulted in rapid changes. Mass printing quickly increased the
circulation of written media and also led to the dissemination of new
forms of written documents, like newspapers and pamphlets. One side
effect was that the augmented availability of written documents
significantly improved the general literacy of the population. This
development served as the foundation for revolutions in various
fields, including science, politics, and religion.

Scientific discoveries in the 19th and 20th centuries caused many
further developments in the history of communication. They include the
invention of telegraphs and telephones, which made it even easier and
faster to transmit information from one location to another without
the need to transport written documents. These communication forms
were initially limited to cable connections, which had to be
established first. Later developments found ways of wireless
transmission using radio signals. They made it possible to reach wide
audiences and radio soon became one of the central forms of mass
communication. Various innovations in the field of photography enabled
the recording of images on film, which led to the development of
cinema and television. The reach of wireless communication was further
enhanced with the development of satellites, which made it possible to
broadcast radio and television signals to stations all over the world.
This way, information could be shared almost instantly everywhere
around the globe. The development of the internet constitutes a
further milestone in the history of communication. It made it easier
than ever before for people to exchange ideas, collaborate, and access
information from anywhere in the world by using a variety of means,
such as websites, e-mail, social media, and video conferences.


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Original Article: http://en.wikipedia.org/wiki/Communication