Based on the above mentioned theory we address the following questions: (1) Do all the SLMs tested generate traditional differences? (2) Do all the SLMs tested generate cumulative cultural change? (3) Does task difficulty enhance cultural phenomena? Here we expect the magnitude of traditional differences to increase with greater task difficulty when learning is more protracted, and that cumulative cultural change will occur when within-lifetime optimization is increasingly limited, which should occur with greater task difficulty; (4) Do SE and OL enhance traditional differences and cumulative culture? Compared to LE, we expect that traditional differences will be enhanced by SE, because SE enhances within-group similarity , and predict that OL will have the same effect. We also expect SE to enhance the cumulative cultural process , and in particular, OL, which leads to direct increases in skill levels, is expected to generate cumulative cultural change of large magnitude; (5) Do cumulative cultural increases in skill level and repertoire quality contribute to energy intake? Next to increases in repertoire quality  we expect increases in skill to contribute to cumulative cultural increases in energy intake. While only OL affects skill learning directly, SE and LE could in principle lead to increases in skill level indirectly. This can happen if LE or SE lead to reduced repertoire diversity and enable foragers to spend their limited skill development time on fewer resources .