Writing argumentative syntheses based on multiple sources implies integrating ideas from different, often conflicting, positions. This can promote more constructive learning, especially when students undertake the task together with their peers. However, despite the importance of this activity in the university context, students generally lack the competency required. Thus, the primary objective of this research is to analyse the impact of a specific intervention programme (CPG + EICS) that combines help designed to foment collaboration with help aimed at improving the writing of argumentative syntheses, improving the quality of the university students' work, whether undertaken individually or collaboratively. For this we designed an experimental study with one hundred and sixty participating psychology students, distributed randomly into four different intervention programmes. We then compared and contrasted the impact of the already mentioned first programme (CPG + EICS) with that of the three others in which we progressively reduced the help provided (explicit instruction with video modelling, a guide and collaborative practice). We evaluated the quality of the syntheses by examining the number of arguments and their degree of integration within the students' texts. The results demonstrate that, to achieve the appropriate competency level, the intervention should include explicit instruction with video modelling. When this instruction combines help aimed at improving the elaboration of argumentative syntheses with help designed to foment collaboration, students integrate a higher level of contradictory information. However, to identify a high level of arguments, explicit instruction focused solely on helping students write argumentative syntheses turns out to be as effective as help directed at collaboration. In addition, after the intervention encouraging collaborative work, students successfully transfer the skills developed to their own individual writing tasks.