A few researchers have summarized the main factors affecting the language learners’ listening comprehension (Boyle, 1984; Parker and Chaudron, 1987; Rubin, 1994). In their taxonomies summarizing the main factors, speech rate is one of the vital causes that influence the listening comprehension. Numerous researchers have also concluded from the participants’ feedbacks and reports that the fast speech rate was a serious factor debilitating the listening comprehension (Boyle, 1984; Friedman and Johnson, 1971; Flowerdew & Miller, 1996; Graham, 2006; Goh, 1999; Hasan, 2000; Su, 2006; Teng, 2002; Vogely, 1995; Yau, 1996). This showed that, recognized by both researchers and language learners, speech rate was one of the major variables that affected listening comprehension. It was therefore plausible that some researchers and teachers would expand, or slow down, the speech rate for the purpose of
increasing language learners’ listening comprehension. Due to this promising
pedagogical implication, slowed-down speech rate has always been one of the major interests in rate studies.
On the other hand, some researchers did not pay much attention to the
slowed-down speech rate. Conversely, they focused on the time-compressed speech, which referred to a speech compressed from the normal speech rate to a faster delivery speed. The listeners therefore had to process more words within the same amount of time as the words processed at the normal or slowed-down speech rate.
Those researchers investigating the time-compressed speech intended to observe the way the hearers reacted to the speech signals delivered at a much faster speech rate.
Both of the researches on slowed-down speech rate and on time-compressed speech are important in providing a more complete understanding of the effect of
speech rate on listening comprehension. The following reviews the studies examining these two modes of speech rate. Section 2.2.1 reviews the studies investigating the effect of slowed-down speech rate. Section 2.2.2 reviews the studies exploring the effect of time-compressed speech on listening comprehension. Section 2.2.3 provides a brief summary.
2.2.1. Studies on the Effect of Slowed-down Speech Rate on Listening Comprehension
The empirical research has yielded inclusive results regarding the effect of slowed-down speech rate on listening comprehension. While some researchers stated that the slowed-down speech rate would facilitate listening comprehension (Kelch, 1985; Griffiths, 1990a, 1990b, 1991a, 1991b), other researchers refuted the assertion that slowed-down speech rate could result in an absolute effect of increased listening comprehension and contented that the effect of the slowed-down speech rate was greatly influenced by the variables with which it interacted (Anderson-hsieh &
Koehler, 1988; Blau, 1990; Teng, 2002). These two conflicting conclusions were addressed in this study as the absolute effect and the relative effect of the
slowed-down speech rate. These two contentions are illustrated respectively as follows.
The Absolute Effect of Slowed-down Speech Rate on Listening Comprehension:
Some previous rate studies have shown that the slowed-down speech rate is the most important facilitator in listening comprehension.
Kelch (1985) attempted to examine the possible effect on listening
comprehension from foreigner talk characterized as slower speech, exaggerated pronunciation, simpler vocabulary and grammar and so forth. Only two characteristics
of foreigner talk, speech rate and grammatical modification, were investigated in Kelch’s study and whether either of these two features was more effective than the other also underwent examination. According to the hypothesis in his study, while the combination of these two modifications would result in the greatest facilitative effect on listening comprehension, the slowed-down speech rate was more credited for the increased listening comprehension compared to the grammatical modification. Also, the slowed-down speech rate could be easily identified as a major variable in listening comprehension.
The results in Kelch’s study were in line with his hypothesis. He therefore concluded that “[o]ther global, syntactic modifications, however, do not necessarily qualify as absolute features of simplification, especially when unaccompanied by slower speech” (p.88) suggesting an absolute effect of speech rate on enhanced listening comprehension. This conclusion confirms the intuitive belief that the slowed-down speech rate is a definite facilitator in listening comprehension.
The study conducted by Kelch showed that the slowed-down speech rate was a significant and absolute facilitator for listening comprehension. However, some methodological problems might dampen its credibility. First, the measurements of listening comprehension designed by the researcher, including the material, test format and scoring method, did not undergo pilot studies before the administration.
The devastation from these unreliable instruments was revealed when the scores obtained in verbatim recall showed significant differences between the slower speech rate and the average speech rate, while the scores in gist recall did not. This
unexpected outcome, criticized by Griffith (1990a), was not well-treated or discussed by the author.
Second, the adjusted speech rate in Kelch’s study which included another 45-second pause between the sentences invalidated the original rates (Griffiths,
1990a), and the intention to discern the individual effect that produces a possible pedagogical theory (Pimsleur et al., 1977). As a consequence, regarding the fact that the pauses were added in addition to the slowed-down speech rate, the study done by Kelch (1985) merely revealed a mixed and also a rather vague effect of the temporal variables on listening comprehension.
Another series of rate studies focusing on the effect of slowed-down speech rate on listening comprehension were reported and conducted by Griffiths (1990a, 1990b, 1991a, 1991b), who borrowed the economic term “cost-effect benefit” to describe the relationship between speech rate and listening comprehension (1990a, p. 311), which could be interpreted as a time-benefit concept. This concept entails that the
slowed-down speech rate provides the listeners with more processing time for the incoming signals. Due to the belief in “cost-effect benefit” or time-benefit concept, Griffiths had conducted experiments (1990a, 1991a) to validate the facilitative effect of slow speech rate, compared to the average and fast speech rate, on listening comprehension.
The study done in 1990a evidenced that the spoken text delivered at the slower speech rate, 100 WPM, was not more comprehensible than the spoken text delivered at the normal speech rate, 159 WPM. However, the study conducted in 1991a revealed a significant difference in listening comprehension between these two modes of speech rate when the slower speech rate was adjusted to 127 WPM and the normal speech rate was adjusted to 188 WPM.
In these two studies by Griffiths showing diverse outcome, it was revealed that the change of the speech rate categorization could in fact manipulate the results, highlighting the central role of speech rate categorization in affecting the outcomes in rate studies. A legitimate speech rate categorization is therefore an essential,
indispensable element in rate studies with regard to its role in dictating a certain
speech rate as slow or fast speech rate, which at the same time determines whether this certain speech rate has facilitative effect or not on listening comprehension. Thus, from which perspective the researchers adopt a speech rate categorization is
extremely important. Researchers hold a different perspective on speech rate
categorization would differ in adopting speech rate categorization, thus arriving at a diverse conclusion.
Another important implication from Griffiths’ studies was that the slowed-down speech rate, when it was too slow, i.e. slower-than-normal speech rate, may have zero or negative effect on listening comprehension. This assumption was derived from his studies where the spoken text delivered at the slower speech rate, 100 WPM, was not more comprehensible than the spoken text delivered at the normal speech rate, 159 WPM. In other words, the 100 WPM speech rate, the “too slow” speech rate, might have zero or negative effect on listening comprehension.
Apart from the discrepancy of speech rate categorization for slow and average speech rate in Griffith’s studies, the instrument utilized to change the speech rate of the listening texts was not considered carefully by the researcher. The listening texts were recorded by a female native speaker with a British English accent through “live voice”, which makes the reach of target rates in all instances difficult, if not
impossible. This shortcoming could be mended easily by using computer-edited software, a more reliable tool, for it could compress or expand speech rate
systematically and show the exact figures for the amount of percentage a text was compressed or expanded along with the indication of WPM. The use of this tool is not only advantageous to language teachers and learners for its simplicity and practicality, but also to future studies when comparing the results with the reference to the
stretched percentage displayed by the computer-edited software.
It was clearly shown in Griffiths’ studies and reports (1990a, 1990b, 1991a,
1991b) that he had a strong belief in and a promising expectation from the slowed-down speech rate operating as a significant and absolute facilitator for listening comprehension, which in fact became the shortcoming in his studies. As discussed earlier, the change of the speech rate categorization to meet his expectation undermined the validity of the results and led the results in the studies to be more of a manipulation than a resolution.
To conclude, though the afore-mentioned researchers intended to validate the slowed-down speech rate as the main facilitator in listening comprehension, its absolute effect on enhanced listening comprehension was still in question.
The Relative Effect of Slowed-down Speech Rate on Listening Comprehension:
Instead of embracing the belief in the absolute effect of increased listening comprehension by slowing down the speech rate of the listening texts, some
researchers asserted that the slowed-down speech rate would only become a factor in listening comprehension when it interacted with other variables, such as proficiency level (Blau, 1990; Teng, 2002), accent (Anderson-hsieh & Koehler, 1988) and syntax (Teng, 2002). In other words, they argued against the absolute effect of speech rate on listening comprehension.
In a study devoted to investigating the interaction effect of speech rate and syntactic complexity on listening comprehension, Blau (1990) designed three versions of treatments: Version 1 was simple sentences at slow and normal speed; Version2 was complex sentences with clues to underlying structure left intact at slow and normal speed; Version 3 was complex sentences without optimal surface clues to underlying structure. The comprehension level was determined by the scores
participants obtained in a multiple-choice comprehension test. The results of the study showed that the only significant variable in listening comprehension was the
participants’ proficiency level and only the low proficiency participants could receive the beneficial effect on enhanced listening comprehension by the slowed-down speech rate. She later concluded that teachers should not be overly concerned with sentence structure and speech rate.
Teng (2002) conducted a similar study to Blau’s (1990) in terms of the variables examined in the study, which are speech rate and syntactic complexity. The context, however, shifted from a mix of EFL and ESL to an EFL only context. The speeds for normal and slow speech rate were slower (160 WPM for normal and 110 WPM for slow), which was based on the speech rate categorized by Pimsleur et al. (1991). The listening test format was True and False (T/F) questions. The results showed that both the syntactic modification and slower speech rate facilitated listening comprehension.
Nevertheless, listening proficiency had the closest relationship with listening comprehension regardless of other variables.
Anderson-hsieh and Koehler (1988) examined the effect of two variables, speech rate and foreign accent, on the listening comprehension of native speakers. The foreign accent referred to the native speakers of Chinese speaking English, and the listening comprehension level of native speakers of American English toward those English speakers with Chinese accent was measured. They concluded that the delivery at the regular rate, compared to fast rate, increased listening comprehension for all speakers. More importantly, a great decrease in listening comprehension was resulted from a heavily accented speaker. Therefore, the study claimed that speech rate would only become an essential variable when the speech was heavily accented.
Blau (1990), Teng (2002), and Anderson-hsieh and Koehler (1988) have shown the effect of other variables interfering with the effect of the slowed-down speech rate on listening comprehension. This point of view provided great insights into the effect of speech rate on listening comprehension. However, the validity of instruments in the
afore-mentioned studies was questionable.
Regarding the speech rate categorization, Blau (1990) criticized in the beginning of her study that different rates were adopted as the norm by different researchers;
however, she defined the speech rate without specifying the rationale (170 WPM for normal speech rate and 145 WPM for slow speech rate). As in Teng’s study (2002), the speech rate categorization was adopted from Pimsleur’s (1977) speech rate categorization that the norm of speech rate was analyzed and defined based on the speech rate of 15 American and 15 French radio news announcers. The application of Pimsleur’s speech rate categorization in Teng’s study thus seemed unsound
considering the fact that Pimsleur’s speech rate categorization including French speakers would not be applicable to categorize the speech rate of American English speakers.
As for the test format, multiple-choice comprehension questions were utilized in Blau’s study, which may induce problems since this format required of the test-takers a certain amount of reading that favored high proficiency participants. The
proficiency level, however, was the variable that the study intended to examine.
Moreover, an English institute entrance exam that shares more resemblance with an in-house test was used to determine the participants’ proficiency level. This type of measurement of listening comprehension, criticized by Berne (2004), would be less reliable, thus limiting its generalizability.
Studies for the effect of slowed-down speech rate on listening comprehension reflected a lack of agreement. This dispute is worth exploring particularly when it comes to the use of authentic material, whose speech rate, based on Vandergrift’s (2007) reports, should not be sacrificed for comprehension since “slowing down the rate of speech is not necessarily helpful for comprehension purpose” (p.200). This study treated this statement with diffidence due to the fact that Vandergrift made this
conclusion based on some unspecified studies and a study conducted by Dewing and Munro (2001) on the effect of the “preferred” speech rate from L2 learners on listening comprehension. The preferred speech rate involves learner’s perception on speech rate, which according to Hasan, (2000), might not be reliable. Therefore, whether slowing down the speech rate could increase listening comprehension of authentic material merits further investigation.
In order to accurately examine whether the slowed-down speech rate was a facilitator or a debilitator in listening comprehension, this study holds the view that it is necessary to further categorize the slowed-down speech rates as the moderately slow speech rate and the slower-than-normal speech rate. These two terms were coined by Tauroza and Allison (1990) in their speech rate categorization where the moderately slow speech rate ranged from 130 to 150 WPM, and the
slower-than-normal speech rate ranged below 130 WPM. These two slowed-down speech rates were respectively compared to the average speech rate which ranged from 150 to 170 WPM. By further categorizing the slowed-down speech rate, this study intended to reveal the possible zero or negative effect of the slower-than-normal speech rate on listening comprehension, thus providing a compelling answer to the effect of slowed-down speech rate on listening comprehension.
2.2.2. Studies on the Effect of Time-compressed Speech on Listening Comprehension
The studies investigating the effect of time-compressed speech on listening comprehension (Conrad, 1989; King and Behnke, 1989) have shown consistent results that the faster speech rate caused burdens on listeners for processing the incoming signals, hence decreasing their listening comprehension level. In addition to the decrease of listening comprehension, additional effects of compressed speech rate on
listening comprehension were also observed. The following discusses briefly these studies examining the effect of time-compressed speech on listening comprehension.
Conrad (1989) pointed out that the time-compressed speech would seriously deteriorate the listening comprehension of low proficiency language learners.
Additionally, students with different proficiency levels would use different strategies to grapple with time-compressed speech.
In Conrad’s study, the participants were 29 native speakers and 28 non-native speakers, who were asked to listen to 16 sentences of nine to eleven words. Each of the sentences, used as a signal for participants to do immediate recall, was repeated five times with the delivery speed compressed to 450, 320, 253, 216, and 190 WPM, representing a progressively slowed-down, or gradually-decreasing, speech rate. The analysis of the recalled message showed that the native speakers depended more on the key content words compared to the non-native speakers. Also, the results showed that native speakers, faced with the speech not being able to be fully comprehended due to the accelerated speech rate, applied their knowledge toward sentence structure to get the maximum amount of information, while the non-native speakers were hindered in their syntactic processing, thus resorting to short-term verbatim memory processing, which resulted in only initial or final elements of the sentences being recalled. In summary, the study done by Conrad demonstrated that, when the delivery speed was fast, the listeners with different proficiency levels would utilize different strategies to cope with the much faster speech rate, and the time-compressed speech rate would seriously deteriorate the listening comprehension of language learners with low proficiency levels.
In King and Behnke’s study (1989), they explored the relationship between the time-compressed speech and three listening types, including comprehensive,
interpretive, and short-term listening. The results indicated that the increased speech
rate significantly dampened the comprehensive listening performance. The interpretative and short-term listening performances, though, were left unaffected until an extremely high degree of time compression was obtained.
According to King and Behnke, the comprehensive listening, the primary focus in the rate studies, might confuse retention and comprehension since it is more associated with long-term memory. In contrast, the short-term listening is more associated with short-term memory, which compared to long-term memory has a closer relationship with compressed speech due to the fact that the faster speech rate prohibited the listeners from processing the message such as elaborated association and inferential meanings. The interpretive listening underscores inference, the nonverbal message and involves “reading between the lines” during listening. The researcher hypothesized that the time-compressed speech has a greater impact on comprehensive listening performance than on short-term and interpretive listening performances, which was supported by the final results.
2.2.3. Summary
By synthesizing the studies examining the slowed-down and the
time-compressed speech, a deeper understanding of the effect of speech rate on listening comprehension would be provided. However, due to the divergent outcomes obtained from investigating the effect of slowed-down speech rate on listening
comprehension, a further exploration is needed in this respect.