CATEGORICAL VS. EPISODIC MEMORY FOR PITCH ACCENTS IN ENGLISH by Amelia E. Kimball, Jennifer Cole, Gery Dell & Stefanie Shattuck-Hufnagel Presented by Ben Posner for the Seminar Exemplar Theorie by Prof. Dr. Bernd Möbius
Categorical Memory vs Episodic Memory
Categorical Features • Stemming from Formal Phonology • Set of abstract representations • Governed by rules and constraints • Models variable error-laden input and output • Remembering is encoding and storing abstract representation • Phonological abstraction
What is Stored in Memory • Each phonetic instantiation of a sound unit is mapped to an abstract category • Only the category of a unit is committed to memory • Different sounds of the same category are indistinguishable in memory
Predictions? • Two distinct sounds mapped to the same category will be reported as the same • Only category is retrievable
Episodic Memory • Exemplar Models • Encode and remember subcategorical phonetic detail
What is Stored in Memory • Episodic memories with all details • All perceived acoustic information (to some extend) • Within Episodes even 'irrelevant' information is stored • Irrelevant to language understanding
Prediction • Within category differences will be remembered • Even subtle differences can be perceived and later recalled
Evidence • Phonological Abstraction • Exemplar Models
Evidence • Phonological Abstraction • Exemplar Models
Phonological Abstraction 1: Goldinger, 2007 • Perception task • Categorical perception of phonemes
Goldinger, 2007 Method • Two sounds that may or may not vary in voice onset time • Participants often unable to detect differences when both sounds are within category • Short-lag memory task instead of perception task(Remembering the f irst sound for a brief amount of time) • Perception task vs. Short lag memory task
Goldinger, 2007 Results • Participants quite bad at the task • Evidence that only category is encoded and retrievable
2: Stress deafness Dupoux, Knaus, Orzechowska, Weise (2008) • Speakers of languages with f ixed lexical stress • Participants do not hear a difference in unfamiliar words with differing stress patterns • In EEG studies differences are perceived but can't be recalled • Evidence that listeners do not remember irrelevant acoustic detail even though it is perceived
Evidence • Phonological Abstraction • Exemplar Models
Exemplar Models (1) McMurrey et al., 2002 • Eye-Fixation Study • Visual World Paradigm
Visual World Paradigm (1) McMurrey et al., 2002 • What • Relies on Cooper (1974), Tanenhaus et al. (1995) • Gaze toward objects in the real world or a visual representation is measured during speech production/perception • How • Eye Tracking in a controlled visual workspace • Why • Natural, Unintrusive • Can be used on people who cannot write/read • Can measure online processing
McMurrey et al., 2002 • Input Signal: Beach vs Peach • Responses: Categorical • But: Eye Fixations driven by subcategorical variation • Evidence that listeners are sensitive to within-category differences
"At perceptual levels, acoustic information is encoded continuously, independent of phonological information" Toscano et al., 2010
Exemplar Models 2: Goldinger, 1996 & Pufal et al., 2014 • Word recognition memory • Up to one week between tests • Task: Identifying whether a word was heard before • Easier with identical background noise (even unrelated noise, e.g. barking dogs) • Evidence for episodic memories of speech that include acoustic detail of within-category variation and linguistically irrelevant variation
Contradictory Evidence • For categorical Perception • Short lag memory/Voice onset differences • Stress deafness • For subcategorical Phonetic Details • Recognition Memory Tasks • Priming Tasks • Do listeners encode subcategorical detail for speech? • → This study
Intonational Pitch Accent • What is that? • Creating accents in words by shifting the pitch instead of other stress patterns (length, loudness, etc.) • In English pitch is part of stress patterns • In Japanese pitch is the sole form of stressing and distinguishes meaning • Sake ↓ ↗ ( 酒 ) = Alcoholic Beverage vs. Sake ↑↘︎ ( 鮭 ) = Salmon
Why Pitch Accents? 3 Reasons
Why Pitch Accents? 3 Reasons • Don't mark lexical contrasts • Lexical contrasts are categorical • Mark Information status distinctions related to focus and accessibility • Focus and Accessibility are gradient
Why Pitch Accents? 3 Reasons • Might not be categorically perceived • Has been looked into but there is no strong evidence
Why Pitch Accents? 3 Reasons • Correlation between Intensity, duration and/or f0 • But: No evidence which of these properties listeners pay attention in perceiving and interpreting pitch accents
2 Types of Variation • Phonological Variation (Presence vs. absence) • Variation in Phonetic Cues to Pitch accent (Duration, F0 peak values) • If pitch accent is encoded and remembered listeners will be sensitive to variation in status variation and phonetic cues • If not only accent status will matter
Study • 6 Experiments • 2 sets of 3 Experiments • Listeners hearing two speech samples after delay or interference • Listeners have to judge whether both samples were identical • Different samples can differ in accent categorically (status) or with sub- categorical change in accent cues
Stimuli • American English • Mostly voiced • "Beavers love building" • Twelve nouns from six sentences (E.g. Beavers and building from above) • Each sentence recorded with four accent patterns • 1&2, 1& ¬ 2, ¬ 1&2, ¬ 1& ¬ 2 • Accented words were synthesised to create a bigger difference (still within original category)
Stimuli • Pitch corrected in Praat • Pitch peak corrected 25 Hz up or down • Duration of word corrected by up to 10% (using PSOLA in Praat) • Differences are detected at the same rate as presence/absence of pitch accent
Participants • 193 total participants • native English speakers from the USA • Age 19 - 59 (mean of 31, standard deviation of 8.4) • Excluded participants who did not f inish or were bilingual • 30 participants per experiment
Procedure • Amazon Mechanical Turk • 6 different Experiments
Experiment 1, 2 and 3 AX Tasks • Two words with one second of silence between • Asked to answer whether recordings were "the exact same recording or different recordings" • Recordings were either the same (1/2 of trials) or differed in one of three ways
Experiment 1 • Variation in Accent Status • Naturally produces accented recording and • Naturally produced unaccented recording of the same word
Experiment 2 • Shortened and Lengthened Version of the Same Recording • Arti f icially shortened version against arti f icially lengthened version • Both resynthesised • No distinction between a natural vs. a resynthesised sample
Experiment 3 • Lowered pitch peak and raised pitch peak • Arti f icially lowered pitch peak against raised pitch peak • Both resynthesised • No distinction between a natural vs. a resynthesised sample
Experiment 4, 5 & 6 • Same as 1, 2 & 3 with delay and interference instead of silence • Four different words (exposure phase) • Followed by tone • Word from exposure phase (Test token) • Question whether test token was exactly the same as the exposure version • More dif f icult • Interference from other words, time delay, and Increased working memory load
Results • For AX task: • Well above chance for all three contrasts • Experiment 1 = 77% • Experiment 2 = 85% • Experiment 3 = 75% • Comparable performance between status difference and duration/pitch changes • All three differences are equally easy to differentiate
Results • With delay and interference • Still above chance • Comparable for Experiment 1 and 4 (Status) • Worse between 2, 3 and 5, 6 (duration and pitch)
Results Accent Duration Pitch AX (Exp 1, 2, 3) 77 % 85 % 75 % Delay (Exp 4, 5, 6) 83 % 67 % 54 % Worse
What does that mean? In Summary • Accent difference (status) is remembered after time lag and in presence of interference • Duration and pitch differences are detectable above chance, less accurately remembered
What does that mean? • Group effects hold when analysed with mixed effect logit model with random slopes and intercepts to accound for individual variability • Individual performance in AX pitch task signi f icantly higher than SD of scored in AX duration task • → more variation from listener to listener in pitch task than in duration or accent task • holds despite excellent discrimiation (of pure tone differences of the same magnitude pitch in post-tests)
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