Effective self-regulated learning, a crucial 21st-century skill, often proves challenging for students, particularly younger ones. One key element is distributed practice—spreading study sessions over time—which enhances long-term retention. However, students frequently fail to adopt this strategy. This study aimed to explore the effectiveness of smartphone-based reminders in promoting distributed practice among lower secondary school students. This age group is particularly relevant because it's a critical period for developing self-regulated learning skills, where students increasingly assume responsibility for their learning. Mobile interventions offer a promising approach, but existing ones often focus on support during study sessions, neglecting the need for proactive support to initiate distributed practice. Reminders, a common feature in behavior-change technologies, serve as nudges—influencing behavior without restricting options or changing economic incentives. While reminders have shown promise in various contexts like mHealth, their potential negative consequences, such as overreliance and hindering habit formation, need consideration. Therefore, this study investigated the potential dual effect of reminders on students' study behavior, acknowledging the possibility of both positive and negative outcomes.

The literature on study reminders for students is limited. While positive effects on studying have been reported, and reminders are widely used in mHealth to promote various regular behaviors (water intake, medication adherence, physical activity), their impact on students' study habits remains unclear. Existing research shows interindividual differences in the effectiveness of reminders, particularly for less frequent events. Studies have also explored optimizing reminder effectiveness through adjustments in timing and frequency, and information content. However, potential negative side effects, such as guilt or annoyance, and the possibility of overreliance (where behavior is only exhibited when prompted) need investigation. This study addressed the gap by investigating the effect of reminders on students' study frequency, considering both potential benefits and detrimental side effects.

This study employed a smartphone-based between- and within-person experimental manipulation with 85 German-speaking fifth graders (mean age 10.67 years; 50.59% female). Participants were randomly assigned to either a Control Group (no reminders) or a Reminder Group (reminders on approximately 16 of the 36 intervention days). All participants used a vocabulary learning app ("cabuu") and a study app. The study app facilitated the ambulatory assessment (daily questions about learning), delivered reminders (for the Reminder Group), and provided a reward system. The vocabulary learning app allowed students to manage vocabulary lists, study, and take tests. On the introductory day, all students received instructions, watched a video on distributed practice, and prepared vocabulary lists. During the 36-day intervention phase, students studied at their own pace, taking tests every ninth day. The Reminder Group received reminders on designated days, displayed as an additional screen after completing the ambulatory assessment. A subsequent 18-day follow-up period continued with vocabulary learning app usage but without reminders. Logfile data from both apps provided objective measures of study behavior and test performance. The primary outcome measures were study frequency (binary: studied/not studied on a given day) and vocabulary test scores. Statistical analyses, including logistic and linear mixed-effects models, were conducted to test hypotheses regarding the impact of reminders on study behavior and test performance. Specific analyses compared study probability on days with and without reminders within the Reminder Group, compared study frequency between groups, and examined the effect of reminders over time.

The study supported the first hypothesis: Students in the Reminder Group were significantly more likely to study on days with reminders (OR = 1.77, 95% CI [1.32, 2.37]). This effect increased over time (b=0.31, 95% CI [0.01, 0.62], χ²(1) = 3.78, p = 0.046). However, the second hypothesis, predicting greater overall study frequency in the Reminder Group, was not supported. There was no significant difference in overall study probability between the Reminder and Control Groups (b=-0.64, 95% CI [-1.41, 0.14], χ²(1) = 2.56, p = 0.106). Further analysis revealed that the increased study frequency on reminder days was offset by significantly lower study frequency on non-reminder days in the Reminder Group compared to the Control Group (b=-0.79, 95% CI [-1.53, -0.05], χ²(1) = 4.23, p=0.037, OR 0.45, 95% CI [0.22, 0.95]). This suggests an overreliance on reminders. There was a non-significant trend indicating that the detrimental effect of reminders increased over time on non-reminder days. No significant difference in vocabulary test performance was found between the groups, which was consistent with the lack of difference in overall study frequency. The analysis investigating the correlation between study frequency and test performance was deemed unreliable due to the noisiness of the test data.

The findings demonstrate a double-edged sword effect of study reminders. While reminders increased study frequency on reminder days, this was counteracted by decreased study frequency on non-reminder days, indicating overreliance. This overreliance is detrimental to self-regulated learning, which aims to foster independent study habits. The study highlights the crucial distinction between simply increasing study frequency through reminders and fostering the automatic, habitual engagement with studying. The lack of difference in vocabulary test performance underscores that frequent studying prompted by reminders doesn't necessarily translate into improved learning outcomes if it doesn't lead to self-sustained study habits. Instead of simply relying on reminders, future interventions should prioritize habit formation by helping students establish cues and routines linked to studying.

This study reveals the limitations of using simple reminders to promote distributed practice. While reminders effectively increased immediate study behavior, they inadvertently hindered the development of independent study habits due to overreliance. Future research should focus on interventions that facilitate habit formation, perhaps by integrating implementation intentions or focusing on identifying and linking study cues to students' daily routines. This should ultimately lead to self-regulated learning and better learning outcomes, minimizing the need for external prompts.

The exploratory nature of the time trend analyses requires confirmation in future studies. The sample consisted of German lower secondary school students aged 10–12, limiting the generalizability to other age groups and learning contexts. The noisiness of the vocabulary test data, due to inconsistent adherence to the testing schedule, impacted the reliability of the analysis examining the relationship between study frequency and test performance. The effects of reminders might be confounded with students' use of the study app itself.