COMPREHENSION OF A NOVEL ACCENT BY YOUNG AND ELDERLY
LISTENERS
Patti Adank1,2 and Esther Janse3,4
1
School of Psychological Sciences, University of Manchester, Manchester, United
Kingdom
2
Donders Institute for Brain, Cognition and Behaviour, Centre for Cognitive
Neuroimaging, Radboud University Nijmegen, Nijmegen, the Netherlands
3
Utrecht Institute of Linguistics, OTS, Utrecht University, Utrecht, the Netherlands
4
Max Planck Institute for Psycholinguistics, Nijmegen, the Netherlands
Running head: Perceiving a novel accent by elderly listeners
Date: February 16, 2016
Address for correspondence:
Patti Adank
Neuroscience and Aphasia Research Unit
School of Psychological Sciences
University of Manchester
Zochonis Building
Brunswick Street
M13 9PL, Manchester, UK
Patti.Adank@manchester.ac.uk
Phone:
0044-161-275 2693
1
ABSTRACT
We investigated perceptual learning of a novel accent in young and elderly listeners
by testing speech-perception-thresholds (SRT) over consecutive blocks of speech
materials. Participants (20 young and 30 elderly) were first presented with four blocks
of Standard Dutch sentences to establish their baseline SRT. Subsequently, they heard
four sentence blocks spoken by the same speaker, but who now spoke in an (artificial)
novel accent of Dutch in which pronunciation of the vowels was systematically
altered. We studied whether both groups show comparable effects of accent on their
SRTs and comparable learning. Both were found to adapt to the novel accent, but the
impact on the SRTs was considerably higher for the elderly group, indicating that
they showed poorer comprehension for the novel accent. Importantly, the results
indicated that the pattern of perceptual learning of the accent differed for the age
groups: whereas the elderly showed minimal learning beyond the second block, the
young adults do show further improvement with longer exposure. Among the elderly
participants, hearing acuity predicted the SRT, as well as the effect of the novel
accent on SRT. Furthermore, a measure of executive function predicted the impact of
the accent on SRT. In sum, these results indicate that accentedness is more
detrimental to speech understanding in elderly than in young adults. The individual
difference analysis of the elderly participants’ data suggests that this may be due both
to poorer hearing and decreased mental flexibility in elderly listeners.
Keywords: speech comprehension, accented speech, aging, hearing, cognitive
factors.
2
INTRODUCTION
Human speech perception is extraordinary in the sense that we are able to learn to
comprehend distorted or unfamiliar speech streams. For instance, listeners can
quickly learn to understand foreign-accented speech (Clarke & Garrett, 2004), noisevocoded speech (Shannon, Zeng, Kamath, Wygonski, & Ekelid, 1995), spectrally
shifted speech (Rosen, Faulkner, & Wilkinson, 1999), synthetic speech (Golomb,
Peelle, & Wingfield, 2007; Greenspan, Nusbaum, & Pisoni, 1988; Pallier, SebastiánGallés, Dupoux, Christophe, & Mehler, 1998; Sebastián-Gallés, Dupoux, Costa, &
Mehler, 2000; Wingfield, Peelle, & Grossman, 2003), and time-compressed speech
(Dupoux & Green, 1997), to name a few. What is most remarkable about this process
is the speed at which it occurs. Listeners generally need exposure to only a handful of
sentences to improve their perception of the novel speech stream (Clarke & Garrett,
2004). This ability to adapt appears to remain stable throughout the lifetime (Golomb
et al., 2007; Peelle & Wingfield, 2005). For instance, Peelle and Wingfield (2005)
tested young adults and older adults’ ability to learn to understand artificially timecompressed sentences and to noise-vocoded and spectrally shifted speech. Timecompression is a method for artificially shortening the duration of an audio signal
without affecting its fundamental frequency (Moulines & Charpentier, 1990). When
both groups were equated for starting accuracy on a sentence-recall task, Peelle and
Wingfield (2005) found that both groups learned at a similar rate and magnitude:
these similarities were found both with respect to adaptation to time-compression and
to the noise-vocoding manipulation. Relative to their 30% accuracy starting level,
both groups showed an improvement of 10-14 percent points after exposure to 20
time-compressed sentences. Note that the speech rate differed across listener groups:
the young listeners adapted to 669 words per minute, while the elderly listeners
3
adapted to 569 words per minute. Elderly listeners have previously been found to
perform less well at understanding time-compressed speech than younger listeners
(Janse, 2009; Peelle & Wingfield, 2005; Wingfield, Tun, Koh, & Rosen, 1999). This
overall poorer performance when processing fast speech has been linked to agerelated hearing loss in elderly listeners (Gordon-Salant & Fitzgibbons, 1993, 2001)
and may also be due to aging of cognitive abilities (Salthouse, 2000b). Janse (2009)
compared young and elderly listeners’ processing of fast (time-compressed) speech
using as task online detection of target words. Elderly listeners’ performance on this
task could be predicted from their hearing acuity, from a cognitive measure reflecting
their relative information-processing speed (the Digit Symbol Substitution task, or
DSS), and from two measures of their reading speed.
In the present paper, we intend to further investigate the relationship between
speech comprehension processes and hearing acuity and cognitive factors. Spoken
language comprehension is important throughout the life span. Therefore,
investigating perceptual adaptation to novel listening conditions in older adults offers
the opportunity to study how perceptual learning is shaped by ‘ear’ and ‘brain’.
Crucially, such an investigation may also yield fundamental insights into the
mechanisms underlying the efficient adaptation in young normal-hearing adults.
To date, there are not that many studies on age-related differences in
perceptual learning for speech comprehension. Apart from earlier studies on whether
aging affects adaptation to temporal or spectral manipulations (Golomb et al., 2007;
Peelle & Wingfield, 2005), 2007), we only know of studies addressing adaptation to
speaker characteristics and amplitude fluctuations in young and older listeners and a
study on ERP correlates of vowel identification (Alain & Snyder, 2008). Studies on
adaptation or learning in other modalities have shown age differences in perceptual
4
learning (Fernandez-Ruiz, Hall, Vergara, & Diaz, 2000; Gilbert & Rogers, 1996;
Kennedy, Rodrigue, Head, Gunning-Dixon, & Raz, 2009 Gunning-Dixon, & Raz,
2009; Raz, Williamson, Gunning-Dixon, Head, & Acker, 2000). The latter study on
the identification of fragmented pictures (Kennedy et al., 2009) investigated whether
age-related decreases in perceptual priming and learning were mediated by
differences in cognitive performance and regional cerebral volume. Variance in
learning of perceptual skill was related to indirect influence of regional brain volume
via mediating cognitive processes. In other words: decreased brain volume in the
older group was associated with cognitive variables (fluid reasoning and verbal
working memory) which in turn were associated with perceptual skill learning. These
results confirmed earlier findings that age differences in learning are associated with
differences in cognitive resources, working memory in particular (Head, Raz,
Gunning-Dixon, Williamson, & Acker, 2002; Kennedy, Partridge, & Raz, 2008;
Rodrigue, Kennedy, & Raz, 2005).
As said, in speech comprehension, cognitive factors in aging often go hand in
hand with age-related hearing loss. Hearing loss also affects perceptual adaptation, as
shown by Sommers (1997). In the present study, we are primarily interested in how
listeners adapt to a naturalistic distortion of the speech signal: variations in the
production of speech sounds resulting from speaking with a foreign or regional
accent. Accented speech represents a variation that (elderly) listeners encounter in
everyday life and that has not been studied before. In our modern-day society, due to
increased mobility and increased multi-cultural influenced in the last 50 years, elderly
listeners are likely to encounter others (possibly including care-givers) speaking with
a foreign or regional accent. This type of variation goes beyond variation in speaker
or speech rate (note that modern time-compression algorithms (Moulines &
5
Charpentier, 1990) do not significantly affect the long-term spectral characteristics of
the original speech signal).
Accented speech (regional or foreign) differs from the standard language in a
number of ways. The variation in foreign-accented speech is generally assumed to
arise from the interaction between the segmental and suprasegmental characteristics
of a speaker’s first (L1) and second (L2) language (Best, McRoberts, & Goodell,
2001; Flege, 1991). For instance, at the segmental level, variation can occur when L2learners produce phonetic contrasts absent in their native language, such as the /l/-/r/
distinction and the /l/-/w/ distinction for Japanese learners of American English. At
the suprasegmental level, it has been demonstrated that L2-learners have difficulties
producing L2-appropriate word stress (Guion, Harada, & Clark, 2004) and intonation
patterns
(Trofimovich
&
Baker,
2006).
Regional
accents
also
exhibit
phonological/phonetic variation at segmental (Adank, van Hout, & Van de Velde,
2007; Clopper, Pisoni, & de Jong, 2005) and suprasegmental levels (Nolan & Grabe,
1996). In sum, accented speech may be assumed to represent phonetic and
phonological variation. Furthermore, variation in foreign and regional accented
speech influences speech comprehension efficiency in native listeners (Adank &
Devlin, in press; Floccia, Goslin, Girard, & Konopczynski, 2006; Munro & Derwing,
1995; Rogers, Dalby, & Nishi, 2004; Van Wijngaarden, 2001). For instance, listeners
show longer response times and make more errors when comprehending speech in a
regional accent they are not familiar with (Floccia et al., 2006), which is aggravated in
noisy listening conditions (Adank, Evans, Stuart-Smith, & Scott, 2009). However,
listeners have also been shown to show more efficient speech comprehension after
short-term exposure (5-15 sentences) to both foreign (Clarke & Garrett, 2004) and
regionally (Maye, Aslin, & Tanenhaus, 2008) accented speech. In conclusion, we
6
argue that accented speech represents a naturalistic type of distortion, and, in analogy
with time-compressed speech, listeners may have initial difficulty understanding it,
but can quickly adapt.
In the present study we investigated first whether elderly adults’ listening
performance is equally affected by accented speech as younger adults’. Second, we
determined whether elderly and younger listeners show a comparable rate and
magnitude of perceptual learning of the accented speech. Third, we aimed to obtain
more insight into the mechanisms underlying the perceptual learning process by
relating elderly listeners’ comprehension of the accented speech and to relate the rate
and magnitude with which they learned to comprehend the accented speech to their
individual hearing acuity and to measures of cognitive function.
Relative comprehension performance of young and elderly listeners was
established
through
an
adaptive
staircase
procedure
involving
sentence
comprehension in noise. In this task, participants were to repeat key words from a
sentence presented in noise. Listeners were presented with blocks of sentences in the
novel accent, and after each block the signal-to noise ratio was established at which
listeners could still correctly repeat 50% of the key words. A decrease in SNR was
used to signify perceptual learning of the accent. (See the Methods section for a
detailed description of the staircase procedure.)
Listeners heard sentences in Standard Dutch and in an accent of Dutch they were
unfamiliar with. This novel accent was obtained by replacing the vowels in stressed
lexical positions, thus creating a non-existing - novel - accent of Dutch. It was
decided to create a novel accent to avoid a confound between speaker and accent,
ensuring that the listeners adapt to the accent and not (only) to the voice of the
7
speaker. Second, using a novel accent to ensures that listeners are all equally
unfamiliar with the accented speech (Adank et al., 2009; Floccia et al., 2006).
Performance on the staircase procedure was related to a measure of hearing
acuity (pure-tone audiometry) and to two cognitive measures for the group of elderly
listeners. The cognitive measures were a measure of information processing speed
(Digit Symbol substitution test, which is part of the Wechsler Adult Intelligence Test,
2004) and the Trail Making Test (TMT), a test of visual attention and task switching.
The latter test is thought to represent a measure of cognitive flexibility. We
investigated whether perceptual learning of a novel accent was associated with
processing speed or cognitive flexibility, or both. Kennedy et al. (2009) found that
fluid reasoning tasks, in which participants had to derive a rule to solve a problem,
were correlated with perceptual learning. Importantly, in Kennedy et al. (2009) the
fluid reasoning tasks and the skill to be learned (fragmented picture identification)
were both in the visual domain. We tried to establish whether cognitive skills tested in
a non-auditory modality could be predictive of listening performance such that
general, rather than modality-specific, cognitive performance can be said to underlie
performance on our listening task.
If comprehension of, or perceptual learning of, accented speech is related to
reduced hearing acuity and reduced cognitive flexibility, then it is expected that the
measures on the staircase procedure task and hearing loss and Trail making test
performance are correlated in the group of elderly listeners.
METHOD
Participants
Two groups of participants, one group of younger participants (20, 5 male, mean 23.3
years, standard deviation 5 years, median 22 years, range 18-41) and a group of older
8
participants (30, 11 male, mean 74.1 years, standard deviation 6 years, median 74.0
years, range 65-87), took part in the experiment. All were native monolingual
speakers of Dutch from the Netherlands, with no history of oral or written language
impairment, or neurological or psychiatric disease. The younger group was not
audiometrically screened, but all stated not having any hearing problems. All
participants in the younger group gave written informed consent and were paid 10
euros for their participation or received course credit. The elderly participants had
contacted the researchers in response to an article in a local newspaper and received
10 euros for their participation. Their level of education was expressed on a scale
from 1-5. The lowest level means that the participant had only finished primary
school, the highest level meaning that one had an academic education. Mean
education of the elderly was 3.6 (range 2-5, SD=1.3). The elderly participants
included in this study showed varying degrees of sensorineural age-related hearing
loss (see Procedure).
Stimuli
The stimuli used in the experiment were identical across both groups. The test stimuli
set consisted of 240 sentences, 120 spoken in Standard Dutch and the same 120
sentences spoken in the novel accent. The sentences were taken from the speech
reception threshold (SRT) corpus (Plomp & Mimpen, 1979a, 1979b), which has been
widely used for assessing speech intelligibility (van Wijngaarden, Steeneken, &
Houtgast, 2002). These sentences were recorded in both accents for a female speaker
of (Standard) Dutch. She was instructed to read Dutch sentences with an adapted
orthography to obtain the sentences in the novel accent. The orthography was
systematically altered to elicit vowel pronunciations as listed in Table I. The novel
accent was designed to merely sound different from Standard Dutch, and was not
9
intended to mimic or replicate any existing accent of Dutch. Only vowels bearing
primary or secondary lexical stress were included in the conversion of the
orthography. The intended (broad) phonetic transcription using the International
Phonetic Alphabet (IPA, 1999) is depicted below the Dutch examples. For example:
Standard Dutch:
“De bal vloog over de schutting”
/də bɑʟ fʟoχ ofə də sχʏtɪŋ/
After conversion:
“De baal flog offer de schuuttieng”
/də baʟ fʟɔχ ɔfə də sχytiŋ/
The recordings were made in a sound-attenuated booth while the sentences were
presented in orthographic form on the screen of a desktop computer. The speaker was
instructed to read the sentences as a declarative statement and with primary sentence
stress on the first noun, as to keep the intonation pattern relatively constant across all
sentences. First, all sentences in Standard Dutch were recorded, followed by those in
the novel accent. Every sentence in the novel accent was repeated until it was
pronounced without errors and judged by the experimenter to sound roughly as fluent
as the Standard Dutch sentences. The average duration per sentence was 2.62 sec for
Standard Dutch and 2.82 sec for the novel accent. The recordings were saved to hard
disk directly via an Imix DSP chip plugged into the USB port of an Apple Macbook.
Praat (Boersma & Weenink, 2003) was used to save all sentences into separate sound
files with begin and end trimmed at zero crossings and re-sampled at 22050 Hz.
Finally, every sentence was peak-normalized at 99% of its maximum amplitude and
saved at 70dB (SPL).
Insert Table I about here
Procedure
Pure Tone Audiometry
10
Hearing acuity (air conduction thresholds for pure tones) was assessed with a portable
Maico ST 20 audiometer in a silent booth. Figure 1 presents the mean pure-tone
thresholds (in dB HL) for the better ear at octave frequencies from 250 Hz to 8000
Hz. The sloping audiogram pattern is typical for age-related hearing loss, which
particularly affects the high frequency range. Individual hearing losses were
determined as the elderly participants’ pure-tone average (PTA) hearing loss over the
frequencies of 1, 2, and 4 kHz in their better ear. Only one participant had hearing
aids, which he was asked not to wear during the experiment. The average PTA was
25.5 dB HL (standard deviation 9.8, median 25.0, range 10-43.)
Insert Figure 1 about here
Digit Symbol Substitution Test
Scores on the Digit-Symbol Substitution test (which is part of the Wechsler Adult
Intelligence Scale Test, 2004) exhibit strong correlations with measures involving
processing speed (Hoyer, Stawski, Wasylyshyn, & Verhaeghen, 2004; Salthouse,
2000a). Elderly participants’ mean substitution time per symbol was 2.1 sec/symbol
(SD=0.4, range 1.5-2.8). This should be corrected for motor speed (the time needed to
copy a symbol), which was 1.0 sec/symbol (SD=0.2, range 0.7-1.4). The corrected
coding time (substitution time minus copying time) was then 1.1 sec/symbol (SD=0.3,
range 0.6-1.9). This latter score was entered as individual information processing
speed.
Trail Making Test
The group of elderly participants also received the Trail Making Test (Reitan, 1958)
as an index of executive control processes. The test is thought to represent a measure
of cognitive flexibility (Corrigan & Hinkeldey, 1987; Gaudino, Geisler, & Squires,
1995; Reitan, 1958). In the written test, the participant is required to connect the dots
11
of 25 consecutive targets on a sheet of paper. In version A of the test, the targets are
all numbers (1-25). Processing speed may be a heavy contributor (Salthouse, 2000a)
to performance on this task. In Test B, the targets are 13 numbers and 12 letters, and
therefore involve shifting attention between numbers and letters (1, A, 2, B, etc.),
while at the same time keeping track of where one was in the other dimension. The
test has to be finished as quickly as possible and thus provides information on visual
search, scanning, speed of processing, mental flexibility, and executive functions.
Performance on this task was shown to be a significant predictor for performance on a
target recall task where the target speaker’s speech was mixed with meaningful
speech of a distracter speaker (Tun, O'Kane, & Wingfield, 2002). Mean time to
complete Trails A was 48.7 sec (SD=14.4). Mean time to complete the Trails B part
was 95.3 sec (SD=27.3). Switching cost (difference score between Trails A and Trails
B) was therefore 46.6 sec (SD=24.1). However, a difference score that is derived from
subtracting the Trails A time from the Trails B time is always greater when the
participant is relatively slow to start with, such that general slowing alone will
produce a greater difference between the conditions (see also (Verhaeghen & De
Meersman, 1998). In order to take general slowing into account, we took ratio scores
of the two Trails A and B subparts (Trails B time/Trails A time), rather than the
difference score, as a measure of individual executive function.
Adaptive staircase procedure
Participants were to repeat key words from a sentence presented in noise.
Listeners were presented blocks of sentences in the novel accent and after each block
the signal-to noise ratio was established at which listeners could still correctly repeat
50% of the key words. A decrease in SNR was used to signify perceptual learning of
the accent. The staircase procedure (Baker & Rosen, 2001) was used to establish the
12
speech reception threshold, or SRT (Kalikow, Stevens, & Elliott, 1977; Plomp &
Mimpen, 1979a) across blocks of 15 sentences. The SRT is expressed using the
signal-to-noise ratio (SNR) in decibel (dB) at which listeners can repeat 50% of the
key words in a sentence. The SRT has been used as a clinical measure of speech
intelligibility for normal-hearing listeners and (elderly) listeners with moderate
hearing loss (Chien, Tu, Shiao, Chien, Wang et al., 2008; Dubno, Dirks, & Morgan,
1984; Gelfund, Ross, & Miller, 1988; van Wijngaarden et al., 2002) and represents a
naturalistic measure of listeners’ comprehension. Another advantage is that the
procedure is well-suited for dealing with individual differences in listeners’ baseline
performance, which may be especially pronounced when groups are heterogeneous.
Earlier studies comparing comprehension in younger and elderly listeners used
calibration tasks prior to their main experiments to match performance levels of the
different groups (Peelle & Wingfield, 2005). It is not necessary to use pre-calibration
when using SRT, as individual performance is kept constant at 50% correct by
continually changing the noise level depending on the participant’s previous response
and individual differences are expressed through its resulting SNR. When one
individual performs the task at a lower SNR than another individual, this means that
they could repeat 50% of key words at a lower SNR (i.e., with more noise added to
the speech signal). A further advantage is that the task is easy to understand and does
not require extensive training. Finally, a recent study evaluated task-related learning
in a speech-in-noise discrimination task using the SRT. Their results showed that
improvements due to task adaptation alone are small (< 1 dB for speech-shaped noise)
when listeners are familiar with the accent and speaker (Cainer, James, & Rajan,
2008), and performance is thus stable throughout the procedure. Given this stability,
Cainer et al. suggest that the SRT can be used to monitor perceptual learning over
13
time. In the present experiment, the adaptive noise task was repeated four times,
presenting listeners with 415 blocks of accented sentences. After each block of 15
sentences, the SRT was calculated. A decrease in SRT reflects perceptual learning.
Gilbert & Rogers (1996) showed that pre-practice in a perceptual learning task was
beneficial, especially for older adults. The four blocks of accented speech were
therefore preceded by four blocks of speech in Standard Dutch, to exclude any task
learning effects during perceptual learning.
Insets Figure 1 about here
The procedure for both Test phases (cf. Figure 2) was identical across both
groups. The SRT (representing the SNR at which 50% of key words are correctly
repeated) was determined using a staircase procedure consisting of a modified Levitt
procedure (Baker & Rosen, 2001). The procedure started with a relatively easy
stimulus at an SNR of +10dB. If this sentence was repeated correctly (i.e., >3
keywords were correctly repeated), the SNR was decreased with 8 dB to +2 dB SNR.
If the participant repeated 2 keywords, the SNR stayed the same. This process was
repeated until the first incorrect response (i.e., <2 keywords were correctly repeated).
After the first incorrect response, the SNR increased with steps of +5dB until the next
correct response. After the next correct response, the SNR decreased with steps of 2dB until the next incorrect response. At this point, each reversal (a correct response
after an incorrect response, or an incorrect response after a correct response, or an
incorrect or correct response following a response with two correct keywords)
resulted in an upward change of 2 dB following an incorrect response, or a downward
change of 2 dB following a correct response. Each block ended after presentation of
15 sentences. The SRT per block was expressed as the mean signal-to-noise ratio
across all trials for which a reversal occurred.
14
The auditory staircase procedure was repeated eight times: four blocks of
Standard Dutch and four blocks in the novel accent. For all eight blocks, participants
were instructed to repeat the entire sentence in Standard Dutch, or as many words as
they had heard. An experimenter immediately scored their responses for the number
of correctly repeated key words. For the blocks in the novel accent, participants were
instructed not to imitate the accent. They received no explicit feedback. The stimulus
presentation rate was controlled by the experimenter and each sentence was presented
only once. Sentences were presented in a semi-randomised order with each sentence
presented only once (either in standard Dutch or in the novel accent) per participant.
This sentence order was counterbalanced across the first four and the last four blocks
and across participants so that every sentence occurred equally often in Standard
Dutch and in the novel accent. Participants were tested individually in a sound-treated
booth. The sentences were presented over headphones (Sennheiser HD477) at a
comfortable sound level. The sound level was set once at a comfortable level for the
younger group and once for the elderly group and this initial setting was not changed
within groups. The duration of the experiment was approximately 30 minutes.
RESULTS
Figure 3 shows the average SRTs in dB for the two accents and the two listener
groups. First, the data of the young and elderly participants were compared to
investigate whether elderly adults’ listening performance is differentially affected by
accented speech than younger adults’ and to compare the course of their perceptual
learning.
Insert Figure 3 about here
15
For the comparison between the young and elderly listeners, we did not enter
individual background information. We only investigated the effects of the following
factors on SRT in a repeated measures ANOVA: the between-subjects factor Age
Group (young vs. elderly), and the within-subjects factors Accent, having two levels
(standard Dutch and novel accent), and Block (with four levels). Age Group had a
significant effect on SRT (F(1,48)=31.3, p<0.001): as can be seen from Figure 3, the
older listeners generally needed more favourable signal-to-noise ratios for 50%
accuracy sentence recognition than the young listeners. The factor Accent also
significantly affected SRTs (F(1,48)=973.7, p<0.001): listeners could stand less noise
when they had to identify sentences spoken in the novel accent than when they were
listening to standard Dutch. There an overall effect of Block (F(3,46)=16.8, p<0.001),
and there was a significant interaction between Block and Accent, indicating that
performance improved more over blocks in the novel accent condition (F(3,46)=7.2,
p<0.001). The overall Block effect suggests that there was some improvement in the
standard Dutch condition (which may have been due to adaptation to the task or
speaker), and that there was additional learning of the novel accent. The interaction
between Age Group and Accent was significant as well, suggesting that the novel
accent was more detrimental to speech understanding for the elderly than the young
listeners (F(1,48)=29.8, p<0.001). The Age Group by Block interaction was
significant (F(3,46)=3.1, p<0.05), suggesting that improvement over the blocks
differed for the two age groups. More importantly, there was also a three-way
interaction between Age Group, Accent and Block (F(3,46)=3.7, p<0.05). The latter
interaction indicates, first, that the pattern of improvement over blocks in the novel
accent condition was different for the two age groups. This is also clear from Figure
3: whereas the elderly hardly show further learning beyond the second block, the
16
young adults do show further improvement with longer exposure. The curve of the
elderly seems to be U-shaped: there is considerable learning from the first to the
second block, and then performance seems to deteriorate again, possibly due to
fatigue. We will come back to this in the Discussion.
In a second analysis, we only analysed the data of the elderly participants to
investigate which background measures predicted performance and perceptual
learning of to the novel accent. Regression analyses were performed to determine the
predictive value of the background measures on the SRTs in both the standard Dutch
and the novel-accent condition.
Apart from the design factor Block, we entered individual hearing acuity, the
digit-symbol substitution time measure of processing speed, the Trail making test
performance measure of executive function, education level, gender, and age, as
background predictors of performance in each of the accent conditions. Our main
question was whether any of these background measures would specifically predict
how well one could understand the novel accent, or how much one would improve
over Blocks. One should note that some of these background measures were
correlated: age was significantly correlated with hearing loss (Pearson’s r=0.42,
p<0.05), and age was also correlated with processing time (Pearson’s r=0.46, p<0.05).
However, the two cognitive measures were not correlated with hearing loss. The two
cognitive measures (digit-symbol substitution time and Trail performance, expressed
as the ratio between TrailA and TrailB) were not correlated (r<0.1). The following
background measures did not predict performance, nor did they interact with Block:
Age, Gender, Educational level, and the measure of information processing speed.
Table II gives an overview of three models for SRT performance in both accent
conditions: the upper half of the table is on SRT performance in the standard-Dutch
17
condition; the lower half of the table is on SRT performance in the novel-accent
condition. In both accent conditions, model 0 only has the factor Block as a predictor
for performance, model 1 has Block and Hearing loss; and model 2 has Block,
Hearing loss, and Trail performance as predictors of performance.
Insert Table II about here
In both accent conditions, Block predicted performance, suggesting a general
improvement in performance over blocks (β=-0.41 in the standard Dutch condition
and β=-0.69 in the novel-accent condition, p<0.01 in both conditions). With the
addition of hearing loss as a predictor (model 1), an additional 15% (in the standard
Dutch condition) of the variance in SRT performance or 20% (novel-accent
condition) was accounted for: the more hearing loss one had, the higher the SRT.
With the addition of Trail test performance as a predictor (model 2), no additional
variance was accounted for in the standard-Dutch condition. However, Trail test
performance did explain a significant additional 4% of the SRT variance in the novelaccent condition. The latter relation indicated that increased relative difficulty in the
executive function task predicted increased difficulty understanding the novel accent.
In the novel-accent condition, a fourth model (model 3) also evaluates individual SRT
(averaged over the four blocks) in the standard-Dutch condition as a predictor for
novel-accent performance. When one's SRT in the standard-Dutch condition is taken
into account, Hearing Loss still accounts for some additional variance (β=0.06,
p=0.05), even though its predictive power is obviously reduced. Trail test
performance (β=0.86, p<0.05) is not much affected, in terms of predictive power for
novel-accent performance, relative to the previous model (model 2).
Note that in these regression analyses, there was also considerable
improvement over blocks in the standard-Dutch condition. Figure 3 shows that this
18
was due mainly to the elderly listeners' relatively poor performance in the very first
block: their performance did not improve beyond block 1 (a separate regression
model on the standard-Dutch condition data from which the first block had been
excluded showed no effect of Block on SRT performance).
Importantly, we did not find that any of the background measures interacted
with Block (or, more specifically, with improvement over blocks in the novel accent
condition). We hypothesised that individual background information would not only
predict performance, but might also predict improvement over blocks. Note that
learning for the elderly participants is concentrated in the first two novel-accent
blocks. We therefore constructed another subset model on the data of the first two
novel-accent blocks. By zooming in on the blocks where learning occurs, we might
find out which (if any) of the background measures are most important for perceptual
learning.
The results of this subset model showed the following. As before, Block
significantly affected performance (β=-2.63, t=-3.61, p<0.001). The same background
measures as in the previous analysis showed up in this subset model. Hearing acuity
had an overall effect on performance (β=0.16, t=4.22, p<0.001). Thus, the more
hearing loss one had, the greater the impact of the novel accent on SRT. And, as
before, Trail performance was associated with performance (β=1.72, t= 2.73, p<0.01),
such that the more difficulty one had in switching between task demands on the Trail
making test, the greater the impact of the novel accent on SRT. By zooming in on
these two initial novel-accent blocks, the predictive power of Trail test performance
has gained in importance somewhat. The latter model including Trail test
performance explained 40% of the variance, whereas the same model without Trail
test as a predictor explained 32% of the variance (i.e., Trail test performance now
19
explained an additional 8% of the variance, compared to the 4% in the analysis over
the four novel-accent blocks). Alternatively, if SRT in the standard-Dutch condition is
entered into the model as well (as in model 3 in Table II), SRTSD significantly
predicted SRT in the novel-accent condition (β=1.69, t=4.82, p<0.001). Hearing loss
was then no longer significantly associated with performance, but Trail test
performance was (β=1.49, t=2.79, p<0.01). However, once again, none of the
background measures interacted with Block, which implies that even if we zoom in
on the blocks where most of the learning occurs, we do not find direct correlates of
perceptual learning.
DISCUSSION
The present study aimed first to compare comprehension of accented speech by
younger and elderly listeners, second to compare adaptation to accented speech in
younger and elderly listeners, and third to relate elderly listeners’ comprehension of
the accented speech and the course of their adaptation to their individual hearing
acuity and cognitive ability.
The results showed three important points. First, the elderly listeners had
considerably more difficulty at understanding the sentences spoken in the novel
accent than the younger group of listeners. Even though elderly listeners’ speech-innoise performance was generally worse than that of the young adults, the elderly
listeners were more affected by the novel accent. This can be seen in Figure 3 from
the distance between two clustered bars (representing performance of the two age
groups at each of the consecutive blocks): whereas the difference between the
clustered bars in the standard Dutch condition was 1-2 dB, the age group difference
was 2-6 dB in the novel accent blocks.
20
Second, the elderly listeners showed a different pattern of learning than the
younger listeners. The elderly start off with considerable improvement: from the first
to the second novel-accent block they even improve more in absolute terms (5.1 dB)
than the young adults over the four consecutive accent blocks (3.8 dB from the first to
the fourth block). Thus, the pattern of learning may be different over blocks for the
two age groups, but adaptation rate was not slower and the magnitude of adaptation
was not decreased for the elderly participants. These results are therefore in line with
Peelle and Wingfield (2005) who found that the rate and magnitude of initial learning
of time-compressed speech and of vocoded and spectrally shifted speech was similar
for young and elderly listeners. The quick learning supports the idea that the ability to
adapt to various new aspects of speech remains stable throughout the life span.
A further similarity to Peelle and Wingfield’s (2005) results is that older adults’
performance reached asymptote relatively early (in their study: in between 10-20
sentences) whereas the young adults still showed improvement at later trials. In our
material, older adults did not improve beyond the second block (which means beyond
30 sentences as each block contained 15 sentences), whereas performance of the
young adults showed a steady improvement till the last block. It is not clear whether
the relatively early asymptote performance for the elderly in our study could have
been due to fatigue. The adaptive-noise procedure makes listening effortful, and
elderly listeners may have become tired after six blocks of effortful listening.
However, the early asymptote pattern was also found in Peelle & Wingfield (2005)
who had a more limited number of sentences. Evidence on perceptual adaptation in
speech comprehension therefore seems to converge that it is not so much the initial
adaptation process that differs between age groups, but the general impact that the
speech manipulation has.
21
The results showed that neither PTA nor both measures of cognitive function
predicted the adaptation pattern in the elderly. Our initial aim was to obtain insights
into the mechanisms underlying perceptual adaptation in speech comprehension by
relating adaptation to the auditory and cognitive background measures. It was
expected that the rate and magnitude of adaptation would differ for the two age
groups, as was found for skill learning in a number of visual modality studies (Head
et al., 2002; Kennedy et al., 2009; Rodrigue et al., 2005). As young and elderly
listeners showed similar rates and magnitudes of adaptation, it may not be surprising
that we could not find associations between adaptation per se and the background
measures. Further research may be required to elucidate how perceptual learning of
novel speech conditions can be relatively unaffected by age, despite the challenges
from age-related declines that older adults obviously face.
However, our results showed associations between auditory and cognitive
background measures and the performance of elderly listeners on the novel accent
sentences blocks. The results showed that both hearing acuity and the measure of
executive function predicted an individual’s relative difficulty in understanding the
sentences in the novel accent. These findings are important with respect to ‘lifelong
learning’ as they elucidate how auditory and cognitive age-related factors interfere
with novel speech conditions. Hearing impairment evidently interferes with
identifying the speech sounds and thus with processing the peculiarities of the novel
accent and the making of novel representations. Executive function is a relatively new
associate of novel task performance, as earlier ‘individual difference’ studies on
perceptual learning in the visual domain mainly found correlations between
perceptual learning and measures of memory or fluid reasoning (Kennedy et al.,
2009). Second, the latter correlations were found within the same modality, as the
22
predictor measures and the to-be-learned skill were tested in the visual domain. Note
that the cognitive measures in the present study were obtained through paper-andpencil tasks. If age-related sensory decline impacted on performance, it must have
been in the visual, and not the auditory, domain. The present results therefore show
that auditory and non-auditory factors can predict listening performance.
A recent aging study showed that decline in executive function (as measured by
Trail making test performance) preceded decline in memory (as measured by
immediate and delayed verbal recall) by about 3 years (Carlson, Xue, Zhou, & Fried,
2009). These results make Trail performance an early measure of the cognitive
flexibility associated with the task of understanding a novel accent.
It has been argued (Birdsong, 2006) that there is a relationship between agerelated morphological neurological changes and the decline in the efficacy of second
language (L2) learning in older adults. For instance, a correlation has been found
between age-related decreases in dopaminergic (DA) functioning and cognitive
processes that mediate L2 learning and L2 proficiency, such as working memory,
attention and processing speed (Volkow, Wang, Fowler, Ding, Gur et al., 1998).
Furthermore, a relationship was found between age-related declines in cognitive
functioning and changes and anatomical neural changes. Measures for working
memory, attention, and speed of processing correlate with volumetric declines in the
frontal lobe and prefrontal cortex (Raz et al., 2000). Following Birdsong's argument,
it may be possible that these age-related functional (DA functioning) and
morphological changes and associated declines in cognitive performance underlie the
poorer comprehension of the novel accent in our elderly listener group.
In sum, investigating perceptual learning of novel listening conditions in
young and older populations offers the opportunity to study how perceptual learning
23
is shaped by ‘ear’ and ‘brain’. Our results add to a growing body of studies addressing
how aging affects speech perception (Golomb et al., 2007; Peelle & Wingfield, 2005).
Our study further confirms results from earlier studies that elderly listeners can adapt
effectively to new speech types. The novelty elderly listeners had to adapt to in the
present study, accented speech, is a naturalistic type of variation they may
(frequently) encounter in everyday life. Finally, the present results show further
evidence that both declining hearing acuity as well as poorer performance at cognitive
function tasks result in poorer language comprehension in challenging or novel
listening conditions.
24
ACKNOWLEDGEMENTS
We wish to thank Erik van den Boogert for technical assistance and Esther Aarts
for lending her voice. Inge van de Sande is acknowledged for her assistance in testing
the elderly participants. We thank Peter Hagoort for his useful suggestions on earlier
versions of this paper. This research was supported by the Netherlands Organization
for Research (NWO) under project numbers 275-75-003 (Patti Adank) and 275-75004 (Esther Janse).
25
REFERENCES
Adank, P., & Devlin, J. T. (in press). On-line plasticity in spoken sentence
comprehension: Adapting to time-compressed speech. NeuroImage.
Adank, P., Evans, B. G., Stuart-Smith, J., & Scott, S. K. (2009). Familiarity with a
regional accent facilitates comprehension of that accent in noise. Journal of
Experimental Psychology: Human Perception and Performance, 35(2), 520529.
Adank, P., van Hout, R., & Van de Velde, H. (2007). An acoustic description of the
vowels of Northern and Southern Standard Dutch II: Regional Varieties. .
Journal of the Acoustical Society of America, 121, 1130-1141.
Alain, C., & Snyder, J. S. (2008). Age-related differences in auditory evoked
responses during rapid perceptual learning. Clinical Neurophysiology, 119(2),
356-366.
Baker, R. J., & Rosen, S. (2001). Evaluation of maximum-likelihood threshold
estimation with tone-in-noise masking. British Journal of Audiology, 35, 4352.
Best, C. T., McRoberts, G. W., & Goodell, E. (2001). Discrimination of non-native
consonant contrasts varying in perceptual assimilation to the listener’s native
phonological system. Journal of the Acoustical Society of America, 109(2),
775-794.
Birdsong, D. (2006). Age and second language acquisition and processing: a selective
overview. Language and Learning, 56(S1), 9-49.
Boersma, P., & Weenink, D. (2003). Praat: doing phonetics by computer.
Downloaded August 11, 2008, from http://www.fon.hum.uva.nl/praat.
26
Cainer, K. E., James, C., & Rajan, R. (2008). Learning speech-in-noise discrimination
in adult humans. Hearing Research, 238, 155-164.
Carlson, M. C., Xue, Q. L., Zhou, J., & Fried, L. P. (2009). Executive decline and
dysfunction precedes declines in memory: The women’s health and aging
study II. Journal of Gerontology A: Biological sciences and medical sciences,
64(1), 110-117.
Chien, C. H., Tu, T. Y., Shiao, A. S., Chien, S. F., Wang, Y. F., et al. (2008).
Prediction of the Pure-Tone Average from the Speech Reception and Auditory
Brainstem Response Thresholds in a geriatric population. Journal for otorhino-laryngology and its related specialities, 70(6), 366-372.
Clarke, C. M., & Garrett, M. F. (2004). Rapid adaptation to foreign-accented English.
The Journal of the Acoustical Society of America, 116(6), 3647-3658.
Clopper, C. G., Pisoni, D. B., & de Jong, K. (2005). Acoustic characteristics of the
vowel systems of six regional varieties of American English. Journal of the
Acoustical Society of America, 118(3), 1661-1676.
Corrigan, J. D., & Hinkeldey, M. S. (1987). Relationships between parts A and B of
the Trail Making Test. Journal of Clinical Psychology, 43(4), 402-409.
Dubno, J. R., Dirks, D. D., & Morgan, D. E. (1984). Effects of age and mild hearing
loss on speech recognition in noise. Journal of the Acoustical Society of
America, 76(1), 87-96.
Dupoux, E., & Green, K. (1997). Perceptual adjustment to highly compressed speech:
Effects of talker and rate changes. Journal of Experimental Psychology:
Human Perception and Performance, 23(3), 914-927.
27
Fernandez-Ruiz, J., Hall, C., Vergara, P., & Diaz, P. (2000). Prism adaptation in
normal aging: slower adaptation rate and larger aftereffect. Cognitive Brain
Research, 9(3), 223-226.
Flege, J. E. (1991). Perception and production: The relevance of phonetic input to L2
phonological learning. In C. Ferguson & T. Huebner (Eds.), Crosscurrents in
second language acquisition and linguistic theories. Philadelphia, PA: John
Benjamins.
Floccia, C., Goslin, J., Girard, F., & Konopczynski, G. (2006). Does a regional accent
perturb speech processing? Journal of Experimental Psychology: Human
Perception and Performance, 32, 1276-1293.
Gaudino, E. A., Geisler, M. W., & Squires, N. K. (1995). Construct validity in the
Trail Making Test: What makes Part B harder? Journal of Clinical and
Experimental Neuropsychology, 17(4), 529-535.
Gelfund, S. A., Ross, L., & Miller, S. (1988). Sentence reception in noise from one
versus two sources: effects of aging and hearing loss. Journal of the
Acoustical Society of America, 83, 248-256.
Gilbert, D. K., & Rogers, W. A. (1996). Age-related differences in perceptual
learning. Human Factors, 38(3), 417-424.
Golomb, J., Peelle, J. E., & Wingfield, A. (2007). Effects of stimulus variability and
adult aging on adaptation to time-compressed speech. The Journal of the
Acoustical Society of America, 121(3), 1701-1708.
Gordon-Salant, S., & Fitzgibbons, P. J. (1993). Temporal factors and speech
recognition performance in young and elderly listeners. Journal of Speech and
Hearing Research, 36(6), 1276-1285.
28
Gordon-Salant, S., & Fitzgibbons, P. J. (2001). Sources of age-related recognition
difficulty for time-compressed speech. Journal of Speech, Hearing and
Language Research, 44(4), 709-719.
Greenspan, S. L., Nusbaum, H. C., & Pisoni, D. P. (1988). Perceptual learning of
synthetic speech produced by rule. Journal of Experimental Psychology:
Learning, Memory, and Cognition, 14(3), 421-433.
Guion, S. G., Harada, T., & Clark, J. J. (2004). Early and late Spanish-English
bilinguals' acquisition of English word stress patterns. Bilingualism: Language
and Cognition, 7, 207-226.
Head, D., Raz, N., Gunning-Dixon, F., Williamson, A., & Acker, J. D. (2002). Agerelated differences in the course of cognitive skill acquisition: The role of
regional cortical shrinkage and cognitive resources. Psychology and Aging,
17, 72-84.
Hoyer, W. J., Stawski, R. S., Wasylyshyn, C., & Verhaeghen, P. (2004). Adult age
and digit symbol substitution performance: A meta-analysis. Psychology and
Aging, 19, 211-214.
IPA. (1999). Handbook of the International Phonetic Association : A Guide to the
Use of the International Phonetic Alphabet. Cambridge: Cambridge
University Press.
Janse, E. (2009). Processing of fast speech by elderly listeners. Journal of the
Acoustical Society of America, 125(4), 2361-2373.
Kalikow, D. N., Stevens, K. N., & Elliott, L. L. (1977). Development of a test of
speech intelligibility in noise using sentence materials with controlled word
predictatbility. Journal of the Acoustical Society of America, 61(5), 13371351.
29
Kennedy, K. M., Partridge, T., & Raz, N. (2008). Age-related differences in
acquisition of perceptual-motor skills: Working memory as a mediator. Aging,
Neuropsychology and Cognition, 15, 165-183.
Kennedy, K. M., Rodrigue, K. M., Head, D., Gunning-Dixon, F., & Raz, N. (2009).
Neuroanatomical and Cognitive Mediators of Age-Related Differences in
Perceptual Priming and Learning. Neuropsychology, 23(4), 476-491.
Maye, J., Aslin, R. N., & Tanenhaus, M. (2008). The weckud wetch of the wast:
lexical adaptation to a novel accent. Cognitive Science, 32, 543-562.
Moulines, E., & Charpentier, F. (1990). Pitch-synchronous waveform processing
techniques
for
text-to-speech
synthesis
using
diphones.
Speech
Communication, 9(5-6), 453-467.
Munro, M. J., & Derwing, T. M. (1995). Foreign accent comprehensibility, and
intelligibility in the speech of second language learners. Language Learning,
45, 73-97.
Nolan, F., & Grabe, E. (1996). Preparing a voice line-up. Forensic Linguistics,, 3(1),
74-94.
Pallier, C., Sebastián-Gallés, N., Dupoux, E., Christophe, A., & Mehler, J. (1998).
Perceptual adjustment to time-compressed speech: A cross-linguistic study.
Memory and Cognition, 26, 844-851.
Peelle, J. E., & Wingfield, A. (2005). Dissociations in perceptual learning revealed by
adult age differences in adaptation to time-compressed speech. Journal of
Experimental Psychology: Human Perception and Performance, 31(6), 13151330.
Plomp, R., & Mimpen, A. M. (1979a). Improving the reliability of testing the speech
reception threshold for sentences in quiet for sentences. Audiology, 18, 42-53.
30
Plomp, R., & Mimpen, A. M. (1979b). Speech reception threshold for sentences as a
function of age and noise level. Journal of the Acoustical Society of America,
66(5), 1333-1342.
Raz, N., Williamson, A., Gunning-Dixon, F., Head, D., & Acker, J. D. (2000).
Neuroanatomical and cognitive correlates of adult age differences in
acquisition of a perceptual-motor skill. Microscopy Research and Technique,
51, 85-93.
Reitan, R. M. (1958). Validity of the Trail Making test as an indicator of organic brain
damage. Perceptual and Motor Skills, 8, 271-276.
Rodrigue, K. M., Kennedy, K. M., & Raz, N. (2005). Aging and longitudinal change
in perceptual-motor skill acquisition in healthy adults. Journals of
Gerontology: Psychological Sciences, 60, 174-181.
Rogers, C. L., Dalby, J., & Nishi, K. (2004). Effects of noise and proficiency level on
intelligibility of Chinese-accented English. Language and Speech, 47, 139154.
Rosen, S., Faulkner, A., & Wilkinson, L. (1999). Adaptation by normal listeners to
upward spectral shifts of speech: Implications for cochlear implants. Journal
of the Acoustical Society of America, 106(6), 3629-3636.
Salthouse, T. A. (2000a). Aging and measures of processing speed. Biological
Psychology, 54(1-3), 35-54.
Salthouse, T. A. (2000b). Steps toward the explanation of adult age differences in
cognition In T. Perfect & E. Maylor (Eds.), Theoretical Debate in Cognitive
Aging. London: Oxford University Press.
31
Sebastián-Gallés, N., Dupoux, E., Costa, A., & Mehler, J. (2000). Adaptation to timecompressed speech: Phonological determinants. Perception & Psychophysics,
62, 834-842.
Shannon, R. V., Zeng, F. G., Kamath, V., Wygonski, J., & Ekelid, M. (1995). Speech
recognition with primarily temporal cues. Science, 270, 303-304.
Sommers, M. S. (1997). Stimulus variability and spoken word recognition. II. The
effects of age and hearing impairment. Journal of the Acoustical Society of
America, 101(4), 2278-2788.
Trofimovich, P., & Baker, W. (2006). Learning second language suprasegmentals:
Effect of L2 experience on prosody and fluency characteristics of L2 speech.
Studies in Second Language Acquisition, 28(1-30).
Tun, P. A., O'Kane, G., & Wingfield, A. (2002). Distraction by competing speech in
young and older adult listeners. Psychology and Aging, 17(3), 453-476.
Van Wijngaarden, S. J. (2001). Intelligibility of native and non-native Dutch speech.
Speech Communication, 35(103-113).
van Wijngaarden, S. J., Steeneken, H. J., & Houtgast, T. (2002). Quantifying the
intelligibility of speech in noise for non-native talkers. Journal of the
Acoustical Society of America, 112(6), 3004-3013.
Verhaeghen, P., & De Meersman, L. (1998). Aging and the Stroop effect: A metaanalysis. Psychology and Aging, 13, 120-126.
Volkow, N. D., Wang, G.-J., Fowler, J. S., Ding, Y.-S., Gur, R., et al. (1998). Parallel
loss of pre and postsynaptic dopamine markers in normal aging. Annals of
Neurology, 44, 143-147.
32
Wingfield, A., Peelle, J. E., & Grossman, M. (2003). Speech rate and syntactic
complexity as multiplicative factors in speech comprehension by young and
older adults. Aging, Neuropsychology and Cognition, 10(4), 310-322.
Wingfield, A., Tun, P. A., Koh, C. K., & Rosen, M. J. (1999). Regaining lost time:
adult aging and the effect of time restoration on recall of time-compressed
speech. Psychology and Aging, 14(3), 380-389.
33
Table I. Intended vowel conversions for obtaining the novel accent. The left column
shows the altered orthography in the Standard Dutch sentences, and the right column
shows the intended change in pronunciation of the vowel in broad phonetic
transcription, using the International Phonetic Alphabet (IPA, 1999).
34
Table II. Results of the three regression analyses on SRT performance in the Standard
Dutch (SD) and novel accent (NA) conditions. For the models with individual
predictors (models 1 and 2), the additional variance explained is indicated, relative to
the previous, simpler, model. Significance: ***p<0.001; **p<0.01; *p<0.05
RT Predictor
β
SD
t
R2
ΔR2
Model 0
Block
-0.41*** -3.40 0.09***
Model 1
Block
-0.41*** -3.75
Hearing loss 0.07***
5.19
0.26*** 0.15***
Model 2
Block
-0.41*** -3.74
Hearing loss 0.07***
5.19
Trail test
0.63
0.13
NA
0.26*** 0.00
Model 0
Block
-0.69**
-2.68 0.06**
Model 1
Block
-0.69**
Hearing loss 0.15***
-3.01
5.67
0.26*** 0.20***
Model 2
Block
-0.69**
-3.07
Hearing loss 0.15***
5.84
Trail test
2.42
1.06*
0.30*** 0.04*
Model 3
35
Block
-0.69*** -3.48
SRTSD
1.46***
5.78
Hearing loss 0.06*
1.98
Trail test
2.22
0.86*
0.45*** 0.15***
36
Figure 1. Mean pure-tone thresholds of the elderly adults (better ear) in dB HL. Error
bars represent standard errors.
37
Figure 2. Design of the experiment. Both groups first listened to four blocks of
Standard Dutch sentences (SD1-4, white), followed by four blocks of sentences in the
novel accent (NA1-4, grey). In each of the 8 blocks, the Speech Reception Threshold
was measured.
38
Figure 3. Average Speech Reception Threshold (SRT) in dB per block of 15
sentences. Dark grey bars represent the group of elderly listeners and the light grey
bars represent the younger listeners. The left four blocks (SD1-4) represent the first
four blocks of Standard Dutch (SD) sentences and the right four blocks (NA1-4)
represent the four blocks of the sentences in the novel accent (NA). Error bars
represent one standard error of the mean.
39
APPENDIX A
Table IV. Sentences from the Speech Reception Threshold corpus (Plomp &
Mimpen, 1979a, 1979b) before and after conversion.
Nr.
Standard Dutch
Novel Accent of Dutch
1
De bal vloog over de schutting
De baal vlog offer de schuuttieng
2
Morgen wil ik maar één liter melk
Moorgen wiel iek mar èn litter meelk
3
Deze kerk moet gesloopt worden
Desse keerk mut geslopt woorden
4
De spoortrein was al gauw kapot
De sportreen waas aal goew kaappoot
5
De nieuwe fiets is gestolen
De niwwe fits ies gestollen
6
Zijn manier van werken ligt mij
Zeen mannir vaan weerken liegt mee nit
niet
7
Het slot van de voordeur is kapot
Het sloot vaan de vordur ies kaappoot
8
Dat hotel heeft een slechte naam
Daat hotteel heft ‘n sleechte nam
9
De jongen werd stevig aangepakt
De joongen weerd steffig angepaakt
10
Het natte hout sist in het vuur
Het naatte hoet siest ien het vur
11
Zijn fantasie kent geen grenzen
Zeen faantassih keent gèn greenzen
12
De aardappels liggen in de schuur
De ardaappels liegen ien de schur
13
Alle prijzen waren verhoogd
Aalle preezen warren verhogt
14
Zijn leeftijd ligt boven de dertig
Zeen lèfteed liegt boffen de deertieg
15
Het dak moet nodig hersteld
Het daak mut noddieg heersteeld
worden
woorden
16
De kachel is nog steeds niet aan
De kaachel ies noog stèds nit an
17
Van de viool is een snaar kapot
Vaan de vij-jol ies ‘n snar kaappoot
18
De tuinman heeft het gras gemaaid
De tuunmaan heft het graas gemajt
19
De appels aan de boom zijn rijp
De aappels an de bom zeen reep
20
Voor het eerst was er nieuwe haring Vor het erst waas eer niwwe harrieng
21
Het loket bleef lang gesloten
Het lokkeet blef laang geslotten
22
Er werd een diepe kuil gegraven
Eer weerd ‘n dippe koel gegraffen
23
Zijn gezicht heeft een rode kleur
Zeen geziecht hèft ‘n rodde klur
24
Het begon vroeg donker te worden
Het beggoon vrug doonker te woorden
25
Het gras was helemaal verdroogd
Het graas waas hèllemal verdrogt
26
Spoedig kwam er een einde aan
Spuddieg kwaam eer ‘n eende an
40
27
Ieder half uur komt hier een bus
Idder haalf ur koomt hir ‘n buus laangs
langs
28
De bel van de voordeur is kapot
De beel vaan de vordur ies kaappoot
29
De wind waait vandaag uit het
De wiend wajt vaandag uut het weesten
westen
30
De slang bewoog zich door het gras
De slaang bewog ziech dor het graas
31
De kamer rook naar sigaren
De kammer rok nar siggarren
32
De appel had een zure smaak
De aappel haad ‘n zurre smak
33
De trein kwam met een schok tot
De treen kwaam meet ‘n schook toot
stilstand
stielstaand
34
De koeien werden juist gemolken
De kujjen weerden juust gemoolken
35
Het duurt niet langer dan een
Het durt nit laanger daan ‘n minnut
minuut
36
De grijze lucht voorspelt regen
De greeze luucht vorspeelt règgen
37
Hij kon de hamer nergens vinden
Hee koon de hammer neergens vienden
38
Deze berg is nog niet beklommen
Desse beerg ies noog nit bekloommen
39
De bel van mijn fiets is kapot
De beel vaan meen fits ies kaappoot
40
De auto heeft een lekke band
De oetoh hèft ‘n leekke baand
41
Het moeilijke werk bleef liggen
Het muj-leekke weerk blef lieggen
42
Het vliegtuig vertrekt over een uur
Het vligtuug vertreekt offer ‘n ur
43
De jongens vechten de hele dag
De joongens veechten de hèlle daag
44
De schoenen moeten verzoold
De schunnen mutten verzold woorden
worden
45
In de krant staat vandaag niet veel
Ien de kraant stat vaandag nit vèl niws
nieuws
46
Door de neus ademen is beter
Dor de nus addemmen ies better
47
Het kind was niet in staat te
Het kiend waas nit ien stat te sprekken
spreken
48
De witte zwaan dook onder water
De wiette zwan dok oonder watter
49
Hij nam het pak onder zijn arm
Hee naam het paak oonder zeen aarm
50
Gelukkig sloeg de motor niet af
Geluukkieg slug de mottor nit aaf
51
De leraar gaf hem een laag cijfer
De lèrrar gaaf heem ‘n lag seeffer
52
Het huis brandde tot de grond toe af Het huus braande toot de groond tuh aaf
41
53
De foto is mooi ingelijst
De fotto ies moi iengeleest
54
Mijn broer gaat elke dag fietsen
Meen brur gat eelke daag fitsen
55
Een kopje koffie zal goed smaken
Een koopje kooffih zaal gud smakken
56
De schrijver van dit boek is dood
De schreeffer vaan diet buk ies dot
57
Zij heeft haar proefwerk slecht
Zee heft har prufweerk sleecht gemakt
gemaakt
58
De sigaar ligt in de asbak
De siggar liegt ien de aasbaak
59
De appelboom stond in volle bloei
De aappelbom stoond ien voolle bluj
60
Er wordt in dit land geen rijst
Eer woordt ien diet laand gèn reest
verbouwd
verbuwd
Hij kan er nu eenmaal niets aan
Hee kaan eer nuh ènmal nits an dun
61
doen
62
De kleren waren niet gewassen
De klerren warren nit gewaassen
63
Het gedicht werd voorgelezen
Het gediecht weerd vorgelèssen
64
Haar gezicht was zwart van het vuil
Har geziecht waas zwaart vaan het vuul
65
De letters stonden op hun kop
De leetters stoonden oop huun koop
66
De groene appels waren erg zuur
De grunne aappels warren eerg zur
67
In het gebouw waren vier liften
Ien het geboew warren vir lieften
68
Lopen is gezonder dan fietsen
Loppen ies gezoonder daan fitsen
69
Het lawaai maakte hem wakker
Het lawwai makte heem waakker
70
Mijn buurman heeft een auto
Meen burmaan heft ‘n oetoh gekoocht
gekocht
71
Als het flink vriest kunnen we
Aals het flienk frist kuunnen we schatsen
schaatsen
72
De kast was een meter verschoven
De kaast waas ‘n metter verschoffen
73
Oude meubels zijn zeer in trek
Oede mubbels zeen zèr ien treek
74
De portier ging met vakantie
De poortir gieng meet vaakkaantih
75
De lantaarn gaf niet veel licht meer
De laantarn gaaf nit vèl liecht mer
76
Door zijn snelheid vloog hij uit de
Door zeen sneelheed vlog hee uut de
bocht
boocht
77
Het is hier nog steeds veel te koud
Het ies hir noog steds vèl te koed
78
De oude man was kaal geworden
De oede maan waas kal gewoorden
79
De bomen waren helemaal kaal
De bommen warren hèllemal llemal kal
42
80
Rijden onder invloed is strafbaar
Reedden oonder ienvlud ies straafbar
81
Onze bank geeft vijf procent rente
Oonze baank geft veef prosseent reente
82
Het verslag in de krant is kort
Het verslaag ien de kraant ies koort
83
In de vijver zwemmen veel vissen
Ien de veeffer zweemmen vel viessen
84
Honden mogen niet in het gebouw
Hoonden moggen nit ien het geboew
85
Een flinke borrel zal mij goed doen
Een flienke boorrel zaal mee gud dun
86
Gisteren waaide het nog harder
Giesteren wajde het noog haarder
87
Het meisje stond lang te wachten
Het meesje stoond laang te waachten
88
De volgende dag kwam hij ook niet
De voolgende daag kwaam hee ok nit
89
Het geschreeuw is duidelijk
Het geschrew ies duudeleek horbar
hoorbaar
90
Eindelijk kwam de trein op gang
Eendeleek kwaam de treen oop gaang
91
De grote stad trok hem wel aan
De grotte staad trook heem weel an
92
De bus is vandaag niet op tijd
De buus ies vaandag nit oop teed
93
Onze dochter speelt goed blokfluit
Oonze doochter spèlt gud blookfluut
94
Ook in de zomer is het hier koel
Ok ien de zommer ies het hir kul
95
Zij moesten vier uur hard werken
Zee musten vir ur haard weerken
96
Niemand kan de Fransman verstaan
Nimmaand kaan de Fraansmaan verstan
97
Eiken balken zijn erg kostbaar
Eeken baalken zeen eerg koostbar
98
Het aantal was moeilijk te schatten
Het antaal waas muujleek te schaatten
99
Er waaide een stevig briesje
Er waj-de ‘n stèffieg brisje
100
De vis sprong een eind uit het water De vies sproong ‘n eend uut het watter
101
Iedereen genoot van het uitzicht
Idderèn genot vaan het uutziecht
102
Het regent al de hele dag
Het regent aal de hèlle daag
103
Het tempo was voor hem veel te
Het teempoh waas vor heem vèl te hog
hoog
104
In juni zijn de dagen het langst
Ien junnih zeen de daggen het laangst
105
De bakkers bezorgen vandaag niet
De baakkers bezoorgen vaandaag nit
106
Het licht in de gang brandt nog
Het liecht ien de gaang braandt noog
steeds
steds
107
De wagen reed snel de berg af
De waggen red sneel de beerg aaf
108
Lawaai maakt je op den duur doof
Lawai makt je oop deen dur dof
109
In de kerk wordt mooi orgel
Ien de keerk woordt moi oorgel gespèld
43
gespeeld
110
De schaatsen zijn in het vet gezet
De schatsen zeen ien het veet gezeet
111
Toch lijkt me dat een goed voorstel
Tooch leekt mee daat ‘n gud vorsteel
112
Hij probeerde het nog een keer
Hee probbèrde het noog ‘n kèr
113
De zak zat vol oude rommel
De zaak zaat vool oede roommel
114
Zij werd misselijk van het rijden
Zee weerd miesselleek vaan het reedden
115
Door zijn haast maakte hij veel
Dor zeen hast makte hee vèl foeten
fouten
116
De nieuwe zaak is pas geopend
De niwwe zak ies paas ge-oppend
117
Dat is voor hem een bittere pil
Daat ies vor heem ‘n biettere piel
118
Op het gras mag men niet lopen
Oop het graas maag meen nit loppen
119
Steile trappen zijn gevaarlijk
Steelle traappen zeen gevarleek
120
De zon gaat in het westen onder
De zoon gat ien het weesten oonder
44