question: How do babies know how to laugh?
comment: I think it is hardwired into us. [Tommy Edison]( URL_0 ) explains it better.
passages: Laughter researcher said: "Laughter is a mechanism everyone has; laughter is part of universal human vocabulary. There are thousands of languages, hundreds of thousands of dialects, but everyone speaks laughter in pretty much the same way." Babies have the ability to laugh before they ever speak. Children who are born blind and deaf still retain the ability to laugh.
   Beginning at birth, newborns have the capacity to signal generalized distress in response to unpleasant stimuli and bodily states, such as pain, hunger, body temperature, and stimulation. They may smile, seemingly involuntarily, when satiated, in their sleep, or in response to pleasant touch. Infants begin using a “social smile,” or a smile in response to a positive social interaction, at approximately 2 to 3 months of age, and laughter begins at 3 to 4 months. Expressions of happiness become more intentional with age, with young children interrupting their actions to smile or express happiness to nearby adults at 8–10 months of age, and with markedly different kinds of smiles (e.g., grin, muted smile, mouth open smile) developing at 10 to 12 months of age.
   Laughter might be thought of as an audible expression or appearance of excitement, an inward feeling of joy and happiness. It may ensue from jokes, tickling, and other stimuli completely unrelated to psychological state, such as nitrous oxide. One group of researchers speculated that noises from infants as early as 16 days old may be vocal laughing sounds or laughter, however the weight of the evidence supports its appearance at 15 weeks to four months of age.
   Provine argues that "Laughter is primitive, an unconscious vocalization." Provine argues that it probably is genetic. In a study of the "Giggle Twins", two happy twins who were separated at birth and only reunited 43 years later, Provine reports that "until they met each other, neither of these exceptionally happy ladies had known anyone who laughed as much as they did." They reported this even though they both had been brought together by their adoptive parents, who they indicated were "undemonstrative and dour." He indicates that the twins "inherited some aspects of their laugh sound and pattern, readiness to laugh, and maybe even taste in humor."
   Infants' emotional exchanges with caregivers begin with purely emotional exchanges, such as smiling or cooing back and forth, or more physical interactions such as when a baby happily responds to hugging, bouncing, or tickling (Bodrova & Leong 2007). Caregivers generally take the initiative in establishing emotional rapport with infants, and infants move from being relatively passive participants to taking increasingly active roles in these dialogues. It has been found that around the beginning of the second month of life, infants begin smiling in response to their caregivers' smile and voice (Zaporozhets & Markova 1983).
   The initial goal of research by Jaak Panksepp and Jeff Burgdorf was to track the biological origins of how the brain processes emotions and social behavior. They compared rat vocalizations during social interactions to the joy and laughter commonly experienced by children in social play. They concluded that the 50-kHz rat vocalizations might reflect positive affective states (feelings or emotions), analogous to those experienced by children laughing during social play.
   Section::::The development of mental processes.:Language.
  
  From birth, babies are learning to communicate. The communication begins with crying and then begins to develop into cooing and babbling. Infants develop their speech by mimicking those around them. Gestures and facial expressions are all part of language development. 
   Instances in which non-human primates have expressed joy have been reported. One study analyzed and recorded sounds made by human infants and bonobos when they were tickled. Although the bonobos' laugh was at a higher frequency, the laugh was found to follow a spectrographic pattern similar to that of human babies.
  
  Section::::Distribution and habitat.
   Crying and vegetative sounds are controlled by the brain stem, which matures earlier than the cortex. Neurological development of higher brain structures coincides with certain developments in infants’ vocalizations. For example, the onset of cooing at 6 to 8 weeks happens as some areas of the limbic system begin to function. The limbic system is known to be involved in the expression of emotion, and cooing in infants is associated with a feeling of contentedness. Further development of the limbic system might be responsible for the onset of laughter around 16 weeks of age. The motor cortex, finally, which develops later than the abovementioned structures may be necessary for canonical babbling, which start around 6 to 9 months of age.
   Section::::Development.:Early age.:Mirth response test.
   There are a few main regions of the human brain associated with humor and laughter. The production of laughter involves two primary brain pathways, one for involuntary and one for voluntary laughter (i.e., Duchenne and non-Duchenne laughter). Involuntary laughter is usually emotionally driven and includes key emotional brain areas such as the amygdala, thalamic areas, and the brainstem. Voluntary laughter, however, begins in the premotor opercular area in the temporal lobe and moves to the motor cortex and pyramidal tract before moving to the brainstem. Wild et al. (2003) propose that the generation of laughter is mostly influenced by neural pathways that go from the premotor and motor cortex to the ventral side of the brainstem through the cerebral peduncles. It is also suggested that real laughter is not produced from the motor cortex, but that the normal inhibition of cortical frontal areas stops during laughter.
   The Laughing Baby video, which was shot by a Swedish man in his kitchen in 2006, has a running time of 1:40, and involves a fixed camera situated on William Nilsson, a blond-haired, blue eyed baby, who laughs after brief interjections from a voice in the background (presumably his father, Kjell-Åke Andersson). The video opens with the Swedish text: "kan man ha roligare" which translates as "Can you have any more fun?"
  
  Section::::The video.:Comments.
   Before even producing a sound, infants imitate facial expressions and movements. Around 7 months of age, infants start to experiment with communicative sounds by trying to coordinate producing sound with opening and closing their mouths.
   These earliest vocalizations include crying and vegetative sounds such as breathing, sucking or sneezing. For these vegetative sounds, infants’ vocal cords vibrate and air passes through their vocal apparatus, thus familiarizing infants with processes involved in later speech production.
  
  Section::::Prelinguistic development (birth – 1 year).:Production.:Stages of pre-speech vocal development.:6-16 weeks: Cooing and laughter.
  
  Infants produce cooing sounds when they are content. Cooing is often triggered by social interaction with caregivers and resembles the production of vowels.
  
  Section::::Prelinguistic development (birth – 1 year).:Production.:Stages of pre-speech vocal development.:16-30 weeks: Vocal play.
   It was once believed that babies could not imitate actions until the latter half of the first year. However a number of studies now report that infants as young as seven days can imitate simple facial expressions. By the latter half of their first year, 9-month-old babies can imitate actions hours after they first see them. As they continue to develop, toddlers around age two can acquire important personal and social skills by imitating a social model.
   Section::::Background.:Scientific approach.:Vocalizations.
  
  From at least the time of Darwin, it has been known that chimpanzees and other great apes also perform a laugh-like vocalization.
   First, infants, even ones that seem vulnerable, are highly capable when they are born. "A newborn already has nine months of experience when she is born," Dr. Brazelton notes. "She is capable of controlling her behavior in order to respond to her new environment."
  
  Second, babies "communicate" through their behavior, which, although it may not always seem like it, is a rational language. Not only do infants respond to cues around them, like their parents' faces, but they also take steps to control their environment, such as crying to get a response from their caregivers.
   Section::::Setting.
  
  In Barrie's 1902 novel "The Little White Bird", in which he introduced the mythos of Peter Pan and the fairies, he wrote, "When the first baby laughed for the first time, his laugh broke into a million pieces, and they all went skipping about. That was the beginning of fairies." The "Disney Fairies" are based on a similar idea: every time a newborn baby laughs for the first time, that laugh travels out into the world, and those that make their way to Never Land turn into a Never fairy.
   Infants are able to imitate facial expressions as soon as their first few days of life according to results retrieved from experiments performed at the Mailman Centre for Child Development at the University of Miami Medical School. 74 newborn babies (with a mean age of 36 hours) were tested to see if they were able to imitate a smile, a frown and a pout, and a wide-open mouth and eyes. An observer stood behind the experimenter (so he/she couldn't see what facial expressions were being made by the experimenter) and watched only the babies' facial expressions, recording their results. Just by looking only at the babies' faces, the observer was more often able to correctly guess what facial expression was being presented to the child by the experimenter. After the results were calculated, "the researchers concluded that...babies have an innate ability to compare an expression they see with their own sense of muscular feedback from making the movements to match that expression."
   The next morning Annie tries to talk to Esther, but the walkie-talkie issues only a faint hiss. She wanders the countryside, checking the walkie-talkie, but no matter where she goes the walkie-talkie is silent. Annie brings drinks and bananas for Esther, tossing the food into the well, but there's still no response from Esther.
   Section::::Behaviour.
  
  Kookaburras occupy woodland territories (including forests) in loose family groups, and their laughter serves the same purpose as a great many other bird calls—to mark territorial borders. Most species of kookaburras tend to live in family units, with offspring helping the parents hunt and care for the next generation of offspring.
  
  Section::::Behaviour.:Breeding.
   Circumstantial evidence supporting the social pre-wiring hypothesis can be revealed when examining newborns' behaviour. Newborns, not even hours after birth, have been found to display a preparedness for social interaction. This preparedness is expressed in ways such as their imitation of facial gestures. This observed behaviour cannot be attributed to any current form of socialization or social construction. Rather, newborns most likely inherit to some extent social behaviour and identity through genetics.
   In 1973, Chapman ran an experiment and found that levels of laughter among 7–8 year-old children were highest when two children listened to funny material together (coaction condition). Furthermore, levels of laughter were higher when one child listened to funny material in the presence of another child (audience condition) than when one child listened to the funny material alone (alone condition). These results indicate that laughter is also socially facilitated.
  
  Section::::Major empirical findings.:Prejudice.
   Another recent study was that of mirror neurons, neurons that fire when mimicking or observing another animal or person that is making some sort of expression, movement, or gesture. This study was again one where neuroscientists used the observations of psychologists to create a model for how the observation worked. The initial observation was that newborn infants mimicked facial expressions that were expressed to them. Scientists were not certain that newborn infants were developed enough to have complex neurons that allowed them to mimic different people and there was something else that allowed them to mimic expressions. Neuroscientists then provided a model for what was occurring and concluded that infants did in fact have these neurons that fired when watching and mimicking facial expressions.
   Section::::Description.
  
  The model provides a graphic representation of the Synactive Theory of development, as applied to both fetal and newborn stages. It focuses upon the infant's within-organism, four subsystems of functioning, and their continuous interaction with each other and with the environment across time (i.e., “together in action,” or synaction). The four subsystems include the:
  
  Autonomic Subsystem: Expressed in the pattern of respiration (e.g., fast, slow, pauses) color changes (e.g., pink, pale, red), neurological indicators (e.g., seizures, tremulousness), and visceral or gut signals such as bowel movements, gagging, and hiccoughing;
  