First, we analyzed the sociodemographic differences between PIU and NPIU, applying the Bonferroni correction for the three sociodemographic variables analyzed, and obtaining an [alpha] of 0.0167 (0.05/3).
We also performed a differential analysis of the two variables related to academic performance across PIU and NPIU (Table 2).
Finally, we analyzed the differences between PIU and NPIU with regard to cognitive performance (Table 3).
As shown in Table 3, we found statistically significant differences between the two groups in relation to the success rate on the perceptual acuity test (z = -2.89, p = .0039), with the PIU group obtaining a higher number of hits (19.18 [+ or -] 5.41) than the NPIU group (17.55 [+ or -] 5.8).
In the first regression analysis (Table 4), stratified according to problematic or non-problematic Internet use, the existence of a positive and statistically significant association between the hit rate in the perceptual acuity test and average school grade (p < .05) was found in the NPIU group, as well as between the error rate in abstract reasoning and the number of failed subjects (p < .01).
With reference to the hypotheses set out at the beginning of this study, it was suggested firstly that students with PIU would experience worse academic outcomes in terms of lower average grades and a greater number of failed subjects than the adolescents with NPIU. This hypothesis has been confirmed in its entirety for the sample assessed, the results being consistent with the findings of previous studies, in which a positive relationship between PIU and scholastic failure has been observed (Huang et al., 2009; Tsitsika et al., 2011; Stavropoulos et al., 2013).
Regarding the second hypothesis, it was thought that, in comparison with adolescents with NPIU, students with PIU would show worse cognitive performance in all the neuropsychological tests applied, measured in terms of higher rates of error and lower hit rates.
Thus, it was found that the adolescents presenting PIU obtained higher hit rates in the perception test than the NPIU group.