Teachers can tailor this learning activity to three difficulty levels to meet students’ needs. 

• Beginners (6-7 years old): – Learners with low cognitive flexibility: Aim of the activity: to practise divided attention, acceptance of unexpected situations, and simple behaviour changes. The instructions should be short and clear (e.g. “If the teacher puts down the chalk, clap twice.”). The chain should be short, involving 4–6 students, so that it remains easy for the children to follow. Events should occur at a slower pace, giving students enough time to observe and respond. The signals should be obvious and easy to notice (e.g. a loud word or a clearly visible movement). The teacher may gently support the process, for example by discussing the instruction with the child in advance or by guiding attention from the background (“Something just happened, watch what comes next!”). After completing the task, students should always receive positive, specific feedback (e.g. “You paid great attention and reacted very well to the signal!”).
• Advanced learners (8-9 years old): – Learners with normal cognitive flexibility: Aim of the activity: to develop attention shifting, tracking parallel processes, and quick reactions. The instructions may be more complex and include multiple steps (e.g. “If someone laughs, stand up and say: That was funny!”). The chain can be longer, involving approximately 8–12 students. The signals are not always very noticeable, so students need to pay attention not only to the main classroom task but also to unexpected events. The pace can be gradually increased to support the development of divided attention and flexible responding. The teacher provides limited support and mainly guides reflection after the activity with questions such as “What helped you notice when it was your turn?” or “What was the most unexpected moment?”
• Experts (9–10 years old): – Learners with advanced cognitive flexibility: Aim of the activity: to develop self-regulation, rapid situation assessment, and adaptive behaviour in complex and unpredictable situations. The instructions may include absurd or multi-step elements (e.g. “If someone who is not your desk partner touches your desk, look to the side, say ‘Wow!’, and spin around once.”). The chain can be long (involving the whole class) and may run on multiple threads, for example with two parallel chains or optional continuation paths. The signals can be more subtle or delayed, requiring students to respond flexibly. Feedback loops can be introduced (e.g. the process returns to a previous participant at some point), increasing the level of concentration. Instructions requiring cooperation may also be included (e.g. “If someone starts singing, clap three times and then ask your desk partner to continue.”). The teacher acts mainly as an observer; students manage the chain reaction independently and then reflect together, for example: “What helped you stay calm when something unexpected happened?”