VOT

Question 1

What are the stages of production for a plosive?

Answer 1

• involves occlusion in the vocal tract. Air pressure then builds up behind the occlusion, which is then released ( this is marked by a transient burst).
• In the case of voiceless plosives, a period of aspiration/turbulence is generated before voicing begins for the preceding vowel. The interval for voiced plosives is much shorter than for voiceless plosives (this interval in known as VOT)

Question 2

What are some examples of plosives and their VOT?

Answer 2

/p,t,k/ are marked by long VOT values, whilst voiced plsoives /b,d,g/ are marked by negative , zero or small VOT.

/p/ = e.g around 100ms VOT

/b/ = e.g around 10ms VOT.

Question 3

What is the definition of VOT?

Answer 3

‘The moment that voicing starts relative to the release of a closure’ Ladeforged 1993

Question 4

What is categorical perception?

Answer 4

It is when listeners appear to perceive speech using phonetic categories. It occurs when we have difficulty discriminating between members of the same category but we are able to discriminate between members of difference categories (their effects are robust )

Question 5

How does the place of articulation of a phoneme effect its VOT?

Answer 5

it effects the VOT values. e.g a bilabial has a relatively small VOT whilst it increases the further back it goes (e.g alveolar velar.. have bigger VOT’s)

Question 6

How does Vowel context effect VOT?

Answer 6

vowels such as [i] for examples have a longer VOT in the plosive next to it rather than [a] for example.

Question 7

How does stress affect VOT?

Answer 7

VOT values are longer in stressed positions

Question 8

How does Rate effect VOT?

Answer 8

Slower speech rates have longer VOT’s on their plosive phonemes.

Question 9

How does speech development effect VOT?

Answer 9

In adult english voiced targets have a short voicing lag, whilst voiceless targets have a long voicing lag. In English Infants there are 5 stages to the speech development process…

Question 10

What are the 5 stages of speech development?

Answer 10

1 = (up to 18 months) all stops fall within the short voicing lag range

2.= (up to 28 months) a distribution begining to emerge with voiceless stops being produced with longer VOT’s though still percieved as voiced.

3 (4 years)- ‘voiceless’ plosives produced with much longer values than adults (overshoot)

4. (6 years) - bimodal distribution of voiced and voiceless plsovies but more variable compared to adults
5. (8/11/puberty) variability gradually reduces to reach an adult like minimum.

Question 11

How does sex effect VOT?

Answer 11

there is some evidence suggesting that they do. Studies have noted longer VOT’s in females for the phonemes /t and d/ (schwartz) /p andb/ (Whiteside and irving 1997) and across all phonemes (Ryalls et al 1997) there are also hormone related differences (Whiteside et al 2004 and wadnerker 2006)

Question 12

How do accent differences affect VOT?

Answer 12

VOT in south yorkshire (voiceless plsovies) have a shorter lag compared to other accents (SSBE)

Plosives in final position may be substituted by the voiceless glottal plsoive (cockney) or glottalised with release (more extreme in newcastle)

may also be affricated which will lengthen VOT values.

Question 13

How does Race effect VOT?

Answer 13

There is also some evidence that VOT varies across races e.g Ryalls et al (1997) found that african americans have longer voicing leads / greater pre-voicing than Caucasian males. (Ryalls et al)

Question 14

What did Whiteside et al (2004) find regarding sex and VOT?

Answer 14

looked at connected speech samples and found that [b ,d, g] displayed significant shorter VOT values for the high- EP phase whilst [p,k] displayed significantly longer VO values in the high EP phase.

Question 15

What Cross linguistic differences are found regarding VOT?

Answer 15

In French, they use different parts of the VOT continuum for voiced and voiceless plosives.

Voiced plosives are characterised by (long) negative VOT values whilst voiceless are characteristics by shrot lag VOT values

e.g the syllable initial in ‘bain’ has a 169.7 ms NEGATIVE VOT whilst ‘pain’ in french the [p] only has a 12.1 ms short lag.

Question 16

What did Theodore et al (2006) find regarding speaker rate and VOT?

Answer 16

VOT increased as syllable duration increased (i.e., rate slowed) for each talker. However, the slopes relating VOT to syllable duration differed significantly across talkers. As a consequence, a talker with relatively short VOTs at one rate could have relatively long VOTs at another rate. Thus the pattern of individual talker differences in VOT is rate dependent.

Question 17

What is Motonobu et al (1979) find regarding VOT characteristics in apraxia of speech?

Answer 17

Each apraxic subject read a randomised list of the japanese monosyllables /de/ /te/ /ge/ and /ke/

Group of apraxic subjects exhibited a considerable oerlap in VOT distribution between voiced and voiceless cognates. It is clear that there is a greater dispersion of productions along the continuum for both voicleess and voiced stops.

Due to the struggle of moving the articulators during speech rather than inaccurately selecting the appropriate phoneme.

Question 18

What was the Purpose of Lisker and Abramsons Cross language study of voicing in initial stops ?

Answer 18

to see how well a single dimension (VOT) serves to seperate the stop categories of a number of languages in which both the number and phonetic characteristics of such categories are said to differ.

Question 19

What were Lisker and Abramsons findings?

Answer 19

VOT may serve as a basis for separating the various manner categories in each of the languages examined. At the same time though there is some indication that the measure of VOT is also sensitive to the place of stop closure , for the velars seem to have consistently higher values than the other stops.

The measure of VOT has been applied to word initial stops in eleven languages and has found to be highly effective as a means of seperating phoneme categories.

Question 20

What did Wadnerker et al (2006) find regarding VOT and the menstrual cycle?

Answer 20

VOT for vocied plosives (b,g) were shorter at the high EP phase, and VOT for voiceless plosives (p,k) were longer at the high EP phase. this resulted in greater voiced voiceless contrast at the high EP phase for both places of articulation

THEN compared to men - found that when VOT for men compared to VOT in low EP phase women, Place or articulation and voicing were significant. however, the sex differences were enhanced at the high EP phase.

Ovarian hormones are known to affect articulatory and neuromuscular system in speech production - so shed light on the supralaryngeal and laryngeal functions regulating speech production.

Question 21

What did Whiteside and Marshal (2000) find regarding VOT and sex and age differences?

Answer 21

As well as perceptual development being important for the development of VOT (distinguishing between the phoneme categories) the development of motor control is also important (e.g articulating the correct consonant production)

• Significant age differences were found between 7-9 groups and 9-11 groups in VOT
• girls had a longer VOT than the boys.
• increase in VOT between 7-9 years but a slight decrease between 9-11 years
• mean VOT values (for all 4 plosives) for girls= 57.3ms and 44.ms for the boys.
• in any developmental study (even in adulthood) there is evidence of changes across the lifespan with VOT, may be due to the sociophonetic factors that should not be overlooked.

Question 22

What did Whiteside Henrey and Dobbin (2003) find regarding VOT and age and motor speech skills in humans?

Answer 22

5-7-9 year olds had a significantly larger co-efficient of varience than the 11-13 year olds.

Results showed that variability in VOT decreased between the data for 5 year olds and those for 11 year olds.

• Pattern found for both the voiced and voiceless plosives.
• this can be interpreted as increased levels of stability of speech output as a function of the maturing motor speech skills.

Question 23

What did Whiteside Henry and Dobbin (2004) find regarding sex differences on VOT and phonetic context effects?

Answer 23

VOT data representing the two different vowel contexts is difficult to ascertain the true extent of the vowel context effects on the VOT values. Requires further investigation.

However the evidence does show that ‘i’ with the preceding plosive does have higher VOT values on all of the 6 plosives (largest difference for ‘ti’ and ‘ta’

For the 13.2 year olds the apparent sex differences may be explained in terms of the sexual dimorphism of the larynx and the vocal tract which emerge during adolescence. females = higher levels of tissue stiffness, may give rise to glottal resistance (resulting in bigger sex differences)

Sex differences for the Voiceless plosive (more marked with vowel /i/ ) suggests that constrictions associated with the vowel /i/ relative to the vowel /a/ may also have underlying sex differences which are contributing to an interaction between sex differences in VOT and vowel context.