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Transcript of Ganong (1980)
Presentation by: Annie McAlpine, Estephanie Ortiz, &
Caleb Saunders ABSTRACT: "To investigate the interaction in speech perception of auditory information and lexical knowledge (in particular, knowledge of which phonetic sequences are words), acoustic continua varying in voice onset time were constructed so that for each acoustic continuum, one of the two possible phonetic categorizations made a word and the other did not. For example, on continuum ranged between the word dash and the nonword tash; another used the nonword dask and the word task. In two experiments, subjects showed a significant lexical effect -- that is, a tendency to make phonetic categorizations that make words. This lexical effect was greater at the phoneme boundary (where auditory information is ambiguous) than at the ends of the continua. Hence the lexical effect must arise at a stage of processing sensitive to both lexical knowledge and auditory information." (Ganong, 110) So... what does that mean? First, we need to understand the
difference between /t/ and /d/.
Both sounds are alveolar stops.
The only difference between the two sounds is voicing. This experiment
produced a series of sounds along a continuum of different voice onset times and asked subjects to identify the words they heard. Voicing is determined by whether or not the vocal chords vibrate when producing a sound. /d/ is voiced. /t/ is voiceless. Voice onset time is a measure of how long the vocal chords vibrate before a stop is released. The experiment created sounds along a continuum ranging from /t/'s VOT to /d/'s VOT. The study found that the more ambiguous sounds on the continuum were determined by the subjects to be lexical, even though the sounds were neither /t/ nor
/d/ The Experiment Experiment 1 Four Alveolar Continuum Pairs Three Velar Continuum Pairs dash and tash
dask and task
dust and tuft
dirt and turf
dose and toast gift and kiss
geese and keep
gush and cusp
The lexical effect seems to be stronger at the voiceless end of the continua than at the voiced end. This pattern was reliable across subjects but not across continua. Most of the effect was caused by the gift kiss continuum pair. Most subjects categorized almost all of the stimuli from the gift-kift continuum as beginning with g. The Experiment Experiment 2 Designed to replicate Experiment 1, with more continuum pairs, to determine if the lexical effect arises the first time a subject hears stimuli from a particular continuum. There is a lexical effect that is significantly stronger at the boundary than at the end of each continuum, showing a larger effect both for subjects and for continua.
The tendency for the lexical effect to be greater at the voiceless end of the continuum in Experiment 1 thus seems to have been a product of the particular words or speech-synthesis strategy used there. 15 25 30 35 40 45 55 in milliseconds So why do this experiment? This experiment is based on the idea of context's notoriety for changing the way we hear sounds and determine if they're lexical. There is a categorical model and a criterion-shift model which predict how people will categorize what they hear. Figure 1 from Phonetic Categorization in Auditory Word Perception, (Ganong 112) Figure 2 from Phonetic Categorization in Auditory Word Perception, (Ganong 114) Table 1 from Phonetic Categorization in Auditory Word Perception, (Ganong 117) Lexical Status Affects: -phonetic categorization at the boundary than at the endpoint stimuli
-"lexical status has an effect before acoustic information is replaced by a phonetic categorization The categorical model was found to be incorrect Additional Auditory Information can be coded at three different levels: -as extra candidate for phonetic categorization
-kept in a raw, uninterpreted form
-as confidence ratings for various phonetic categorizations
What model was being tested by this experiment?
What is VOT?
Which has a greater VOT; /t/ or /d/? Why?
What phenomena was discovered during this experiment? This experiment challenged the categorical model which provided an expected interpretation of words and nonwords across a VOT based continuum. The model was found to be incorrect.
VOT stands for voice onset time, and is a measurement of vibration released before a stop or plosive.
/d/ has a greater VOT than /t/ because /d/ is voiced and /t/ is voiceless.
This experiment discovered that significant lexical effect occurs in the more ambiguous boundary along a VOT continuum. Ganong, William F. "Phonetic Categorization in Auditory Word Perception." Journal of Experimental Psychology 6.1 (1980): 110-25. Web. 24 Jan. 2013.