Behavioral Contagion (04:03)

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Cognitive Neuroscientist Sophie Scott studies human voice. She uses a Skype Laughter Chain to illicit response, testing impulsiveness of behavior. When laughing, air flows from the lungs through the larynx in contractive bursts.

Instinctual and Cognitive (04:55)

Prof. Robert Provine observes laughter in public places and learns that it follows rhythmic patterns, is typically not preceded by humorous conversation, and is a social behavior. He distinguishes laughter types; some encourages bonding and others send interpretive signals.

Involuntary and Controlled Sorts (05:31)

Prof. Carolyn McGettigan researches whether brains differentiate spontaneous and social laughing; she plays a recording for children who accurately identify both. MRI scans show laughter types trigger different neural areas. Humans have evolved specific motor systems for controlling vocalizations.

Maternal Instinct (05:51)

Susan Lingle tests the responses of animal mothers to babies crying; she believes mammal caregivers are hardwired to answer. She plays recordings of different species in distress; mule deer run to the rescue while trying to determine the source.

Ancient Reaction (04:37)

Provine believes laughter evolved from primate ancestor's labored breathing during rough games. Biologist Marine Davila-Ross finds primates vocalize when tickled. She reconstructs the evolution of sounds and determines laughter is at least 13-million-years-old and an invitation for play.

Developing a Sense of Humor (04:59)

Prof. Gina Mireault researches how babies determine what is funny, establishing the Laughing Baby Lab to test social and cognitive theories. Experiments show that infants as young as five months laugh at absurd events without cues.

Trained Response (05:51)

Newborns spend two hours a day wailing. Prof. David Haley studies how infants impact their parents' brains. Mothers wear electroencephalography caps and undergo concentration tests in silence, with baby laughter, and crying. When a caregiver successfully soothes their child, dopamine releases.

Adult Crying (07:07)

Basal and reflex tears are functional. Professor Ad Vingerhoets attempts to determine the purpose of crying. He sets up a chamber to test whether hypoxia triggers a response and concludes that oxygen deprivation impacts emotionality, but feelings of powerlessness are the true cause.

Instinctive Vocalizations (07:39)

Only humans produce emotional tears. Marc Baker studies individuals prone to the behavior. He quantifies facial response with a thermal imaging camera, observing biological reactions. Scientists discuss health benefits of crying and laughing.

Credits: Laughing and Crying (00:32)

Credits: Laughing and Crying