With the rapid development of Internet and multimedia technology, online learning has become a widely accepted form of learning. Online open courses with instructional videos as the core are constantly emerging. Instructional videos provide learners with rich and high-quality digital learning resources. Learners can learn knowledge by using computers, tablets and smart phones at anytime and anywhere. With the development of online education, the use of instructional videos is increasing all over the world. How to design instructional videos reasonably has become an important topic in the research of online courses.
Although a lot of research has been done on whether a lecturer appears or not in the video, the way of interaction, the type of instructional video, etc., the discussion on subtitle types, the lecturer’s speed rate and the characteristics of the learners is insufficient. Subtitles and speech rate are important ways of presenting information in English instructional videos. Besides, learning style is one of the most important factors that affect the effect of learning. Therefore, it is necessary to study the influence of the type of subtitles and the speed rate on the learning effect based on the learning style of the learners in order to find a reasonable way of designing and developing English instructional videos. This study explores the effects of subtitle types and speech rates according to the learner’s learning style on cognitive load, learning flow and academic achievement. For the purpose of experiment, six videos with different subtitle types (no subtitle, English subtitles, Chinese-English Subtitles) and speech rates(slow speed, fast speed) were developed. Before the experiment, students’ prior knowledge level of culture shock and intercultural adaptation, and their learning style were examined. A total of 231 students from the second and third grades of English major at Hebei University, China, were randomly assigned to six groups. Their cognitive load, learning flow and academic achievement were measured after video learning. SPSS 25.0 software was used for data analysis and multivariate analysis of variance was carried out.
According to the research hypothesis, the main results of this study are summarized as follows:
1. In English instructional video learning, subtitle types have statistically significant influences on learners’ cognitive load, learning flow and academic achievement. The learners who studied the videos with Chinese-English subtitles had the lowest cognitive load, the highest learning flow and academic achievement.
2. In English instructional video learning, lecturer’s speech rate has statistically significant influences on learners’ cognitive load, learning flow and academic achievement. Learners who studied the videos at low speech rate had lower cognitive load, higher learning flow and academic achievement than those who studied the videos at fast speech rate.
3. In English instructional video learning, the interaction of subtitle types and lecturer’s speech rate had no statistically significant effect on learners’ cognitive load, learning flow and academic achievement. Learners who studied videos with Chinese-English subtitles and slow speech rate had the lowest cognitive load, and the highest learning flow and academic achievement. Learners who studied videos with no subtitle and fast speech rate had the highest cognitive load, and the lowest learning flow and academic achievement.
4. In English instructional video learning, the interaction of the subtitle types and the learners’ learning style had statistically significant effect on learners’ cognitive load, but did not have significant effect on learning flow and academic achievement. The academic achievement of learners with verbal learning style was higher than that of learners with visual learning style.
5. In English instructional video learning, the interaction of the lecturer’s speech rate and the learner’s learning style had statistically significant effect on learners’ cognitive load, learning flow and academic achievement. When learning videos with slow speech rate, learners of visual learning style had better learning performance, while when learning videos with fast speech rate, learners of verbal learning style had better learning performance.
Based on the above research results, the following enlightenments for the design and development of English instructional videos can be drawn.
First, in English instructional video learning, subtitles help EFL learners understand the video content. Instructors should choose the appropriate type of subtitles according to the teaching objectives. When the teaching task focuses on the understanding of the video, bilingual subtitles are the best choice.
Second, fast speech rate has a negative impact on learners'' memory and understanding. When learners learn English instructional videos with slow speed rate, the learning effect is better. Therefore, instructors should choose the appropriate speed rate according to the learners'' English level when designing English instructional videos.
Third, for learners of visual learning style, the learning effect is better when learning videos with slow speech rate. However, fast speech rate can improve the learning effect of learners of verbal learning style. Therefore, instructors can use video playback software to adjust the playback speed, so that the speech rate of the instructional video can meet the differentiated needs of students.
Fourth, in English instructional video learning, if the ways of information presentation match the learning style of learners, better learning results can be obtained. The learning style should be considered as an important variable when designing instructional videos, which helps to improve the learning effect of learners in the online learning environment.