This study examined the educational impact of lecture videos that incorporated TTS technology on dental hygiene students, with a focus on cognitive outcomes, effective learning and satisfaction with the learning experience. Although the 60% attrition rate among respondents might appear to be high, it should be noted that comparable or even higher rates of attrition have been reported in the context of online surveys and learning environments in previous studies. For instance, Rahmani et al. [10] and Shaikh & Asif [11] emphasize that attrition rates in online higher education and surveys, particularly in settings with voluntary participation, commonly range between 30% and 60%. Consequently, the 60% attrition rate employed in this study was a conservative estimate that ensured sufficient statistical power and accounting for potential non-response bias.

The TTS-based group achieved overall mean cognitive scores around the midpoint, with several items, particularly problemsolving, long-term retention, and concentration, falling below 3.0. These results indicate that learners perceived constraints in cognitive depth provided by TTS-based instruction rather than simple neutrality toward the format. The consistently low cognitive ratings appear to stem from structural limitations inherent to synthesized speech. Reduced prosodic variation and limited expressive cues likely weakened attentional regulation and hindered semantic organization, thereby lowering perceived clarity and problemsolving support [12,13]. The absence of dialogic interaction and adaptive pacing further constrained higher-order reasoning [14].

Caution is warranted in interpreting these findings, as the observed effects may reflect limited engagement with higher-order cognitive processes such as problem-solving and applied reasoning. Compared with lecture videos recorded by human instructors, which provide paralinguistic cues such as intonation, stress and emotional tone to guide attention and regulate cognitive load, TTSbased narration lacks expressive modulation. This reduced naturalness may hinder learner’ ability to process complex concepts and to distinguish essential content from supplementary information during cognitively demanding segments [12,13].

Emerging research indicates that TTS voice profiles influence learning differently. Voices with richer prosody enhance attention and reduce cognitive load, whereas flatter voices diminish engagement [12]. Although this study employed two contrasting profiles, it did not measure voice-specific effects. Future studies should systematically compare acoustic features to determine which profiles optimize cognitive and effective outcomes.

Despite cognitive limitations, learners reported strengths in clarity and ease of review, consistent with studies indicating that TTS enhances accessibility and content revisitation [7,8]. Moreover, previous studies have shown that AI-based learning content can enhance self-directed learning by enabling learners to control their study pace and engage in repeated practice [9]. This finding aligns with the results of the present study, which indicated that specific groups of learners, particularly first-year students with less academic experience, experienced significantly greater cognitive benefits. Consequently, TTS-based lectures may offer potential benefits during the initial phase of learning, particularly in supporting the acquisition of introductory concepts.

However, the lower cognitive ratings found among second and third year students, many of whom fell below the midpoint, suggest that TTS-based lectures may not have met the cognitive expectations of more advanced learners. There learners typically require richer explanatory depth, adaptive feedback, and sophisticated conceptual scaffolding. This interpretation is consistent with research indicating that learners’ expectations for instructional depth and interactivity increase with academic level, making low prosody and low interaction TTS formats less suitable for advanced coursework [15,16]. Thus, the grade level differences in cognitive outcomes appear more closely tied to pedagogical fit and instructional design misalignment than to learner ability itself.

No significant differences related to age were observed in the effective learning outcomes, yet substantial grade-level variations were evident. First-year students achieved higher scores in learning interest, learning attitude, and perceived educational value than sophomores. In multiple areas, including interest, attitude and value, their scores also surpassed those of juniors. This phenomenon aligns with principles of motivational design theory. According to Keller’s ARCS model, attention and relevance are proximal drivers of satisfaction. Entry-level learners often demonstrate a heightened sensitivity to novelty and relevance cues embedded in new media [17].

Beyond the realm of motivation theory, extensive research in the field of online learning has emphasized the pivotal role of course and instructor design, alongside dialogic interaction, in shaping learner satisfaction and perceived learning outcomes. These findings lend support to the notion that novice learners, who rely more heavily on structure and guidance, exhibit stronger positive emotional responses when the learning material is meticulously scaffolded [15,16]. The findings of this study are consistent with this account. The higher effective ratings, such as interest and attitude, among first-year students align with this perspective. However, the lower ratings observed in second-year students suggest the presence of an expectation-experience gap, necessitating targeted design improvements, as discussed in this study.

Emerging evidence suggests that synthetic voices have the capacity to influence learners’ emotions and engagement in different ways. Several comparative studies have reported divergent perceptions of AI-generated and human voices. Indeed, there are instances in which specific synthesized voice styles have been shown to negatively impact attention and learning performance. This may help explain the muted emotional responses observed when prosodic cues are limited [18,19]. As posited by CharpentierJiménez [18] and Jing et al. [19], the accessibility and potential for repeated viewing afforded by TTS can support positive emotions by reducing effort and enabling self-paced learning. This is particularly advantageous for novice users [14].

No significant age differences were observed in learning satisfaction, except for content clarity. However, multiple grade-level disparities emerged in areas such as content clarity, voice appropriateness, interest, convenience, time/place flexibility, intention to re-watch, usability, positive impact on learning, and overall satisfaction. First-year students demonstrated the highest levels of satisfaction, while sophomores consistently exhibited the lowest. Notably, time/place flexibility had the strongest significance in the present study. These findings align with established models of online learner satisfaction [15,16]. Such models suggest that course design and structure, instructor support and dialogic interaction are key predictors of satisfaction and perceived learning. These factors tend to benefit novice learners, who rely more heavily on scaffolding and a predictable structure.

The importance of flexibility and usability in our data is consistent with the idea that course flexibility, perceived ease of use, system quality, and course quality are critical determinants of e-learning satisfaction [20,21]. Sun et al. [20] and Martin and Bolliger [21] posit that the combination of on-demand access and the ability to rewatch TTS video lectures plausibly increases convenience and perceived control. This, in turn, supports satisfaction via the attention–relevance–confidence–satisfaction linkages described by Keller’s ARCS model [17]. As Keller [17] asserts, voice characteristics have been shown to influence satisfaction. However, recent experimental findings have reported instances in which synthesized voices diminish attention and engagement compared to human voices. This phenomenon may reduce effective responses and subsequent satisfaction, particularly when prosody is constrained [19]. Jing et al [19] argue in their study that the lower sophomore ratings observed across several items in the sample can be attributed to a growing expectation-experience gap, whereby students progress and seek richer prosody, dialogue, and instructor presence [15,16].

The present study demonstrated strong positive correlations between cognitive outcomes, effective learning, and learning satisfaction (r=0.94–0.95, p<0.01). This indicates that learners with a deeper understanding of the content tend to be more emotionally engaged and report higher satisfaction with the learning experience. This finding is consistent with the theoretical perspective that learning is influenced not only by cognitive processes, but also by emotional responses such as interest, perceived value and attitude. These emotional responses act as motivational drivers of internal engagement and sustained effort [17]. Furthermore, previous research in online and technology-supported learning environments has shown that emotional involvement enhances cognitive processing, and that positive emotions contribute to satisfaction, which in turn reinforces continued learning behaviors [15,16].

Despite these insights, several limitations should be acknowledged. Firstly, the study was conducted at a single institution with a sample limited to dental hygiene students, which may restrict the generalizability of the findings. Future research should include diverse academic disciplines and multiple institutions samples to enhance external validity. Secondly, reliance on self-reported data introduces the possibility of response bias. Incorporating objective measures such as pre/post-tests or behavioral metric would provide a more comprehensive understanding of learning outcomes. Thirdly, the absence of qualitative analyses limited insight into learner’ subjective experiences with TTS, including discomfort with voice quality or the role of repeated playback. A mixedmethods approach could capture nuanced perceptions of prosody, fatigue, and learning strategies [14]. Fourthly, the lack of interactivity and human voice elements in TTS videos may have constrained engagement and cognitive processing. Exploring hybrid models that integrate TTS with human narration or adaptive feedback is recommended. Lastly, longitudinal studies are needed to assess the sustained impact of TTS-based instruction on knowledge retention and skill transfer. Given that novice learners in this study reported higher effective satisfaction, future studies should also consider tailored engagement strategies for intermediate learners to bridge potential expectation–experience gaps [14–16].

Taken together, the results highlight that cognitive understanding, emotional involvement and satisfaction are mutually reinforcing elements of the learning process. Therefore, optimizing TTS-based lectures in dental hygiene education should involve enhancing informational clarity. It should also include the deliberate design of emotionally engaging, learner-centered experiences, such as interactive elements, relatable clinical examples, and adaptive pacing support. These improvements are likely to enhance cognitive, emotional, and satisfaction outcomes, thereby strengthening the instructional value of TTS-based resources in both foundational and advanced learning contexts [15–17]. Future research should continue to refine these approaches to ensure that TTS-based resources can serve not only as supplementary tools but also core components of effective, inclusive, and engaging digital education.