Final answer:
The main weakness of Barton et al (2002) is the potential lack of sufficient evidence to support the main ideas, with the study possibly containing too many generalities.
Step-by-step explanation:
One weakness of Barton et al (2002) is that their research might contain insufficient evidence to effectively support their main ideas. This concern often arises when studies attempt to cover a broad range of topics without delving deeply into specific areas, which results in too many generalities rather than concrete, specific facts. Such issues can stem from trying to achieve too much within a constrained timeframe or publication space, impeding the ability to provide a robust and detailed argument.