Hauser+and+Fitch+-+What+are+the+Uniquely+Human+Components+of+the+Language+Faculty?


 * 9.1 Introduction
 * Language
 * Present in almost all humans.
 * Affected by neural circuitry.
 * Exhibits development.
 * Is constrained and has parameters.
 * Language is an adaptation, therefore it can be studied.
 * No fossils to study (organs don't fossilize well).
 * No living species are similar enough to humans to study.
 * Must study language through two approaches.
 * Phylogenetic Approach: Creating a timeline of human language evolution.
 * Comparative Approach: Comparing data studied in other species in order to learn about human language development.
 * Hauser and Fitch
 * Believe that the phylogenetic approach has been explored, but only leads to more questions and "storytelling."
 * Believe that the comparative approach is useful in studying language evolution as well as the current state of language.
 * Want to focus on comparative studies of the faculty of language, specifically on the //"...sensory-motor system involved in the production and perception of acoustic signals"// (1-2).


 * 9.2. Speech Production
 * A basic understanding of the physics and physiology of speech attained over fifty years ago providing necessary first step for adequate analysis and synthesis of speech.
 * Only recently, extremely basic questions concerning animal sound production have become the focus of concerted research.
 * Adequate understanding of the evolution of acoustic communication systems requires mature theories of both production and perception.

9.2.1. Source--Filter Theory of Animal Vocal Production >>
 * Describes Speech production as a two stage process involving the generation of a sound source, with its own spectral shape and spectral fine structure, which is then shaped or filtered by the resonant properties of the vocal tract.

9.2.1.1. The Sound Producing Source
 * Original function of the larynx was to protect the airway by acting as a gatekeeper to respiratory system.
 * The tertiary function of the larynx in mammals produces sounds.
 * It contains paired vocal cords which are set into vibration by air flowing through the glottis

9.2.1.2. The Vocal Tract Filter
 * The vocal tract includes the pharyngeal, oral, and nasal cavities.
 * Their size and shape determine the complex formant pattern of the emitted sound.
 * Human vocal tract differs from other primates, human larynx rests much lower in throat.
 * Lowered larynx allows humans to produce wider range of formant patterns than other mammals
 * Descended larynx believed to be unique to humans.

9.2.2. Communication with Formants: The Comparative Perspective
 * //"Formants are present in vocalizations and perceived by animals"// (8).
 * Formants
 * Contain clues to an individuals identity.
 * Help identify the body size of the vocalizer.
 * The frequency of formants are mainly influenced by the vocal tracts length.
 * And the skull largely influences the length of the vocal tract.

9.2.3. Convergent Evolution: The Descent of the Larynx in Non-humans
 * Why does the larynx descend in some species?
 * Theories
 * Increases propagation of sounds.
 * Exaggerate the size of the vocalizer (intimidate rivals and help attract females).
 * Are these factors convergent with the evolution of a descending larynx in humans?
 * The second descent of the larynx in male humans is probably similar to the reason for deers; to make the voice exaggerate the size of the male.

9.2.4. Speech Production: Conclusions and Future Directions
 * The evolution of vocal imitation should be studied more.
 * Hierarchical composition also should be studied in more depth.

9.3. Speech Perception
 * Different sounds associated with human emotion (such as crying, laughter) as opposed to hearing spoken language engage different neural circuits.

9.3.1. Categorical Perception and the History of the "Speech is Special" Debate
 * Categorical perception is the ability to divide speech sounds into discreet categories.
 * To determine what part of categorical perception is tied to speech and unique to humans, researchers studied adult human reactions to non-speech acoustic signals, infants to language, and animals in the same way categorical perception was discovered in humans.
 * Studies discovered that birds and other animals possess the same ability.
 * Categorical perception is therefore not unique to humans, but a general auditory mechanism.

9.3.2. Beyond Categorical Perception
 * It currently appears that the mechanisms that allow for speech did not evolve only for that purpose.
 * Humans are able to distinguish between prototypical (expected) and non-prototypical (less fitting of the norm) phonetic categories, otherwise known as the perceptual magnet effect. This means that members of species with this ability can distinguish between good/prototypical and bad/non-phonemes.
 * Birds also have this ability, but our closer relatives do not- this means the structures must have evolved at least twice, and is not unique to humans.

9.3.3. Spontaneouly Available Mechanisms for Speech Perception in Animals
 * Studies thus far have shown that there is no uniquely human speech mechanism. Some argue that this is because the animals are trained, and these studies do not accurately show how they spontaneously react to stimuli.
 * Therefore, studies compare human infants/children to animals.
 * Habituation/dishabituation: subjects are first acclimated to sounds from one acoustic class, then exposed to other sounds that deviate in a specified way. Responding to the new stimuli means the subject is capable of perceptual discrimination, while if they acclimate to the sound shows evidence that they are capable of clustering/grouping sounds across habituation/test stimuli. This also showed whether or not they could categorize different varieties of sound.

9.3.3.1. The Role of Rhythm in Discriminating Human Languages
 * Since human and animal hearing share so many commonalities, animals may be able to distinguish between languages even if that is not something they have evolved those skills for.
 * Both human infants and tamarin were able to distinguish between languages in the majority of the tests; both groups failed when the audio samples were played backwards.
 * This proved 5 points:
 * 1) The habituation/dishabituation method is useful for studying similarities/differences in perceptual mechanisms, while avoiding the pitfalls of training.
 * 2) Animals, like tamarins, listen to both the isolated syllables and strings of speech equally.
 * 3) Some animals are capable of extracting acoustic equivalence classes.
 * 4) Since animals cannot distinguish language differences when the samples are played backwards, they must be looking at properties of speech as well as "low-level clues"- they can distinguish between languages based on rhythmic classes.
 * 5) Since both groups scored less well with recorded tracks, especially with the tamarins, it is likely infants and the test animals respond to different acoustic cues.

9.3.3.2. Speech Segmentation and the Implementation of Statistical Learning Mechanisms
 * How do infants determine where a word starts/ends, given the conflicting acoustic clues?
 * Infants are equipped with the ability to compute computation statistics- they are able to guess, based on experience, which sounds are likely to follow other sounds and determine words based on that.
 * After performing similar tests on animals, it was found that other species also have this ability to intrinsically use statistical learning mechanisms.
 * In order to make irrefutable conclusions, these studies would need to be repeated with the exact same methodology for both animals and infants; at present, they differ slightly.

9.4. The Future of Comparative Studies
 * Many of the subsystems that produce/perceive speech are present in other animals, both closely and distantly related to us. Therefore, they must have evolved for other functions, with speech being a byproduct.
 * Human language is still unique for its ability to endlessly produce new output
 * In the future, we should look at how non-human animals adapt their ability to process acoustics/noises based on familiarity and exposure.

Vocabulary
 * Formants: "Acoustic resonance" or ranges in a sound spectrum.
 * Hypertrophy: The enlargement of an organ or tissue due to an increase in the size of its cells.
 * Lexicon: The vocabulary of a person, language, or branch of knowledge.
 * Parse: Analyzing a sentence into component parts and describing their syntactic roles.
 * Vocal Tract: Pharyngeal, oral, and nasal cavities.
 * Australopithecines: A bipedal hominid family that originated between 10 and 5 million years ago.