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Based on cognitive load theory, the variability effect occurs when learners’ exposure to highly variable tasks results in better test performance. Using four randomised controlled trials in the area of secondary and tertiary mathematics instruction, the present study investigated the effects of variability, with an emphasis on levels of instructional guidance and levels of learner expertise. Experiments 1, 2 and 4 hypothesised that learners who study fully-guided worked examples will yield higher post-test performance scores, compared to learners who attempt unguided problem-solving tasks (Hypothesis 1); and learners who study high-variability worked examples will yield higher post-test performance scores, compared to learners who study low-variability worked examples, with no difference being generated under problem-solving conditions (Hypothesis 2). Hypothesis 1 was not supported in Experiments 1, 2 and 4, while Hypothesis 2 was supported only in Experiment 2. The variability effect that was produced in Experiment 2 led to further investigation in Experiment 3, where it was hypothesised that more-experienced learners (experts) would demonstrate the variability effect, and less-experienced learners (novices) would demonstrate a reverse variability effect. This hypothesis was supported, producing a classic expertise reversal effect. In addition, in all four experiments, learners’ cognitive load was evaluated by having each participant complete a subjective rating of difficulty scale upon completion of their learning tasks. The results supported the assumptions based on cognitive load theory: learners in the worked-examples groups experienced less cognitive load compared to the problem-solving groups (in Experiments 1, 2 and 4); novices experienced less cognitive load when solving low-variability problems compared to high-variability problems, and lower cognitive load was experienced by experts, compared to novices, for both high- and low-variability tasks (in Experiment 3); and cognitive load associated with the completion of high-variability tasks was higher compared to the completion of low-variability tasks (only in Experiment 4). Although it is well grounded in empirical evidence that learners should be provided with worked examples during the initial stages of learning, these results strongly suggest that learners should be initially presented with low-variability problems, and as their levels of knowledge advance, variability should increase.

This study analysed the Chinese character learning process through the concerns of the Cognitive load theory, an instructional approach that emphasises human cognitive architecture and its evolution to provide evidence-based instructional design principles and effects. In cognitive load theory research, element interactivity has been considered as the fundamental and defining mechanism influencing cognitive load. After identifying complex interactive elements within a Chinese character, Isolated Elements and Variability Effects of Cognitive Load Theory were used to alter the element interactivity in Chinese characters when instructing novice learners in writing characters using worked examples-practice procedures. Two experiments were designed to alter the element interactivity in Chinese characters using the corresponding teaching procedures. A number of characters with more than eight strokes-movements were disassembled into three individual components. The students were required to trace examples and practice writing of either repeated sequences of individual isolated components followed by integrated components of full characters (Isolated – Integrated sequences); or conventional Integrated – Integrated full characters trace and practice with strokes-movements sequences only. In Experiment 1 (34 Australian university students learning Chinese language), the suggested procedure was tested with three characters. In Experiment 2 (72 international students at a Chinese university), an additional condition of variable sequences of isolated components followed by integrated components (Variability – Integrated sequences) was added and tested with a group of five characters. It was hypothesised that the fully integrated stroke-movements form of practice sequences would result in less learning due to a greater cognitive load. The results demonstrated that the participants in both the Isolated-Integrated and Variable-Integrated groups performed significantly better than the Integrated-Integrated group, with the Variable-Integrated group outperforming the Isolated-Integrated group in Experiment 2. The suggested instructional techniques have clear implications for improving teaching of Chinese characters writing skills.

Accent variability is an emerging field of study in listening to varieties of English. Mutual intelligibility of accent variations in monolingual, as well as multilingual settings may become challenging for native as well as non-native speakers of English. In a CLT framework this thesis examined the accent variability effect and the expertise reversal effect in listening to native and foreign-accented English with different levels of expertise groups. The three experiments reported in this thesis addressed issues of how accent variability boosted meaningful understanding of listening comprehensions, and how instructional design could aide learning in perceptual listening environments so that learners did not become entangled in the novelty of the accents; at the same time maximising the learning of such instructional procedures.In Experiment 1 three single-accent conditions and six multiple-accent conditions were used. The accents were Australian English, Chinese-accented English and Russian-accented English. These three accents were permuted in six combinations to have the six multiple-accent conditions. The results of Experiment 1 did not support the hypotheses. The low expertise learners did not perform better in single-accent conditions and the high expertise learners did not perform better in multiple-accent conditions. In Experiment 2 Russian-accented English and Australian English were employed. The results partially supported the hypotheses. It was found that the single-accent condition was not easier for the low expertise students whereas the dual-accent condition was easier for the high and very high expertise students. In Experiment 3 the low expertise group listening to Indian-accented English found the accent condition easier than the low expertise group listening to both Indian and Arabic-accented English. The high and very high expertise students learned more listening to Arabic and Indian-accented English than listening to Indian-accented English only. The low expertise individuals were more prone to be challenged by the novelty of the dual-accent conditions. The findings of the experiments were explained in terms of accent variability effect and expertise reversal effect in a CLT framework. Instructional design, as pertaining to this thesis facilitated the naïve, as well as expert English language learners’ abilities in extracting accent-independent global adaptation to English within a CLT framework.