*3.2. Clustering Function*

23 groups were found using the clustering function, with 9 of these groups containing a significant number of publications; however, the remaining 14 groups only reached 1.5% (Figure 6).

With regards to clustering parameters, a resolution value of 1.0 (default value in CitNetExplorer software) was considered, and the minimal publication size for each group was 500.

Table 2 shows the information from the citation networks on the nine main groups, ordered from largest to smallest according to their size.

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**Figure 6.** Clustering function in the network of citations on academic performance.


**Table 2.** Citation network information on the nine main groups.

In group 1, 3223 articles and 11,097 citations were found across the network. The most cited publication was the article by Richardson et al. [21], which was published in 2012 in the Psychological Bulletin, and it also ranked first among the 20 most cited publications. In this group, the different articles analyzed the impact of personality, cognitive ability, self-discipline, motivation, and demographic and psychosocial factors on academic performance (Figure 7).

In group 2, 1095 publications and 4407 citations were found across the network. The most cited publication in this group was the article by Hillman et al. [33], which was published in 2008 in Nature Reviews Neuroscience. In this article, the authors concluded that physical exercise leads to greater physical and mental health throughout life. The articles in group 2 dealt with the influence of visual impairments, such as uncorrected refractive errors, on academic performance. The articles in this group also analyzed the association between the number of hours spent watching television and obesity, as well as the positive impact that a healthy lifestyle, such as a healthy diet or practicing physical exercise, has on cognitive skills and academic performance (Figure 8).

In group 3, 971 publications and 2638 citations were found across the network. The most cited publication was the article by Ferguson et al. [30], which was published in 2002 in the British Medical Journal. This paper analyzed the requirements for predicting future academic performance, such as previous academic ability, personality, learning, or personal references. The common topic in this group was how personality, demographic data, and mental (depression, anxiety, and stress) and emotional (motivation) states influence academic performance. These papers also considered the academic selection process, focusing specifically on careers in the field of health (Figure 9).

**Figure 7.** Group 1 citation network.

**Figure 8.** Group 2 citation network.

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**Figure 9.** Group 3 citation network.

In group 4, 776 publications and 1354 citations were found throughout the network. The most cited publication was the article by Fuligni et al. [41], which was published in 1997 in Child Development. This article analyzed how family background, parental attitudes, and peer support influence the academic performance of immigrant students. The common theme in this group was the influence of psychosocial and economic factors, such as family, teachers, peers, gender, or corrected refractive errors on academic performance (Figure 10).

**Figure 10.** Group 4 citation network.

In group 5, 734 publications and 1567 citations were found throughout the network. The most cited publication was the article by Crede et al. [42], which was published in 2010 in Review of Educational Research. In this publication, the authors concluded that class attendance has a positive impact on grades. The common subject in group 5 was the relationship between students who attend class and those who work, and the impact of this on academic performance (Figure 11).

**Figure 11.** Group 5 citation network.

In group 6, 665 publications and 1107 citations were found throughout the network. The most cited publication was an article by Duncan et al. [43], which was published in 2007 in Developmental Psychology. In this article, the authors analyzed cognitive, attention, and socio-emotional skills in terms of academic performance. The common topic in this group was the relationship between the said skills, drug use, bullying, and delinquency, and academic performance (Figure 12).

In group 7, 640 publications and 2407 citations were found throughout the network. The most cited publication was an article by Curcio et al. [29], which was published in 2006 in the journal Sleep Medicine Reviews. In this publication, the authors analyzed the impact of sleep on academic performance. The common topic addressed by this group was the impact of sleep and stress on academic performance (Figure 13).

In group 8, 619 publications and 1587 citations were found throughout the network. The most cited publication was an article by Dupaul et al. [44], which was published in 1991 in School Psychology Review. This study analyzed the academic performance of children with behavioral disorders. The common topic in this group was how hyperactivity disorders influence academic performance (Figure 14).

**Figure 12.** Group 6 citation network.

**Figure 13.** Group 7 citation network.

**Figure 14.** Group 8 citation network.

In group 9, 591 publications and 1772 citations were found throughout the network. The most cited publication was an article by Kirschner et al. [28], which was published in 2010 in Computers in Human Behavior. This study analyzed the negative impact of social networks, such as Facebook, on academic performance. The common subject in this group was the influence of digital devices and social networks on academic performance (Figure 15).

**Figure 15.** Group 9 citation network.

Table 3 shows a more detailed description of the oldest and most recent publications from the nine main groups.



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Figure 16 shows that, after analyzing the relationship among the different groups by means of the drilling down function, no connection has been found between the main publications in different groups.

**Figure 16.** Relationship between the nine major groups.
