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BMC Med Educ
BMC Med Educ
BMC Medical Education
1472-6920
BioMed Central London

39261852
6000
10.1186/s12909-024-06000-1
Matters Arising
Does lecture playback speed not affect memory and concentration in medical students?
Nakhostin-Ansari Amin a-nansari@alumnus.tums.ac.ir

https://ror.org/01c4pz451 grid.411705.6 0000 0001 0166 0922 Sports Medicine Research Center, Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Iran
11 9 2024
11 9 2024
2024
24 99319 7 2024
6 9 2024
© The Author(s) 2024
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
Merhavy et al.’s study on the impact of lecture playback speeds on concentration and memory is valuable as it is one of the few studies on how different playback speeds may affect medical students’ learning. However, despite the novelty of this study, some limitations concerning its methodological rigor, including statistical analyses, lack of evaluation of confounders, unclear characteristics of participants, and lack of a true control group, need to be considered in the interpretation of findings.

Keywords

Concentration
Memory
Playback speed
issue-copyright-statement© BioMed Central Ltd., part of Springer Nature 2024
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pmcI read Merhavy et al.’s article entitled “The impact of lecture playback speeds on concentration and memory” with great interest [1]. The study is valuable as it is one of the few studies on how different playback speeds may affect students’ learning in the context of medical education. I have some points to add regarding this study, which I believe may impact the way we interpret the findings.

First, no information is provided on the basic and demographic characteristics of the participants and their academic history, which may affect the generalizability of findings and confound the effects of playback speed on memory and concentration. For example, previous studies have shown differences in memory functions and memory processing between males and females [2, 3]. Additionally, students with different learning abilities have different performances across playback speeds, and the optimum playback speed for the best performance differs between them [4]. However, no information is provided on the participants’ prior academic performance as a measure of their learning ability and their sex. Consequently, it is not possible to control the findings for participants’ sex and their prior academic performance. The possibility of overrepresentation of high-performing medical students or a specific gender in the study should be taken into account when interpreting the results. Specifically, an overrepresentation of students with stronger learning abilities could potentially mask differences in the effects of 1.5x and 2x playback speeds, as these students may adapt to faster playback speeds more readily. Furthermore, approximately 77% of the participants usually watched lectures at 1.5x playback speed or faster, suggesting they might already have adapted to faster lecture viewing.

Second, another key element that is missing in the article is the timing of the post-intervention assessment. In a similar study by Kıyak et al., which compared the effects of lecture normal and 2x playback speeds on memory retention among medical students, even though the total test score was not significantly different between groups one week after the intervention, there were differences between groups concerning the answers to two questions. In contrast, no significant differences were observed between groups regarding their total test scores and answers to individual questions immediately after the intervention [5]. Throughout the current article, it is mentioned that the effects of lecture playback speed on long-term memory is assessed. However, the article lacks crucial details about the timing of the post-intervention assessment, which again may impact the findings. One may assume that assessments were performed immediately after the intervention. Still, it needs to be clearly stated in the manuscript, and in this case, the short follow-up is another limitation of the current study. Moreover, there are no details regarding the words spoken per minute in the lectures, which is another limitation of the study. This factor is crucial as the findings are influenced by the rate at which words were spoken, with listening comprehension diminishing as the word rate per minute increases [6]. An increased word-per-minute rate in lectures would lead to further declines in students’ performance when listening at faster playback speeds compared to lectures with a lower word-per-minute rate.

Third, the study lacks a proper control group, and the results do not support the conclusions sufficiently. 1.5x playback speed was chosen as the control, which is considered a proxy of 1x playback speed. A study conducted by Song et al. is referenced by the authors as the basis for this decision, as they argued that there were no significant differences between individuals listening to podcasts at 1.5x and 1x playback speeds in Song et al.’s study. Song et al.’s study itself is notably limited by a lack of information on words per minute in podcasts, a particular focus on the ultrasound radiology topic, which relies on visual input, and the circumstance where students listened to podcasts at 1.5x playback speed before 1x playback speed [5, 7]. It is also important to note that even in Song et al.’s study, the outcomes varied depending on the podcast topic. For example, when participants engaged with a podcast on ultrasonography artifacts, those who listened at 1x playback speed exhibited significantly better performance in the post-intervention quiz compared to those who listened at 1.5x speed [7]. Furthermore, statistically, it is plausible that there may be no significant differences in the effects of watching lectures at 1.5x playback speed compared to the effects of watching at 1x or 2x playback speeds. Still, it does not rule out the possible differences between the effects of watching lectures at 2x and 1x playback speeds. Therefore, 1.5x and 1x playback speeds may not be used interchangeably. Consequently, the conclusion that “students may listen to lectures using lecture playback speed at 1.5x to 2x speed without a decline in concentration or memory of content” is not supported by the result, as there was no control group in the study watching the lectures at 1x playback speed. A more conservative conclusion would be that in students who used to watch lectures at an increased playback speed, an increase of playback speed from 1.5 to 2 does not appear to affect memory and concentration negatively.

Finally, statistical tests used in the study could be enhanced by using non-parametric tests and making within-group comparisons. Even though the changes from pre-intervention to post-intervention scores are reported, no statistical tests are used to assess their statistical significance. Furthermore, there are inaccuracies in some of the reported average scores in the article. (e.g., average pre-intervention concentration game score in the 1.5x group of the second cohort). As the authors have made the underlying data available, I reperformed the analyses using SPSS version 26. As quiz scores can be considered an ordinal variable, and none of the variables were distributed normally according to the Kolmogorov-Smirnov test (p < 0.005), I used non-parametric tests, including Mann-Whitney and Wilcoxon tests, rather than parametric tests to perform the between-group and within-group-comparison (Table 1). Even though the findings are overall compatible with what the authors reported in the article, making within-group comparisons provides further insight into how playback speed affects quiz and concentration game scores as the quiz scores significantly improved after the intervention (p < 0.05), and there were no significant changes in the concentration game scores (p > 0.05).

Table 1 Comparison of concentration game and quiz scores before and after the intervention between groups

Variable	Group	Before the intervention	After the intervention	Within-group comparison	
Median (IQR)	P-value (Mann-Whitney test)	Median (IQR)	P-value (Mann-Whitney test)	P-value (Wilcoxon test)	
Cohort 1	
Concentration game	1.5x group	2.1 (1.6)	0.599	1.6 (0.9)	0.599	0.394	
2x group	2.1 (0.8)	1.6 (0.7)	0.301	
Quiz score	1.5x group	3 (2)	0.74	5 (1)	0.572	0.003	
2x group	3 (1)	5 (1)	0.001	
Cohort 2 & 3	
Concentration game	1.5x group	30 (11.25)	0.335	31 (9)	0.103	0.67	
2x group	27 (9.5)	25 (9.5)	0.67	
Quiz score	1.5x group	3 (2)	0.096	6 (3.25)	0.386	0.014	
2x group	5 (3)	6 (3)	0.001	
IQR, interquartile range

To conclude, despite the novelty of Merhavy et al.’s article, some limitations concerning its methodological rigor, including statistical analyses, lack of evaluation of confounders, unclear characteristics of participants, and lack of a true control group, need to be considered in the interpretation of findings.

Acknowledgements

Not applicable.

Author contributions

Amin Nakhostin-Ansari conceptualized the study and drafted the manuscript.

Funding

Not applicable.

Data availability

No datasets were generated or analysed during the current study.

Declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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