The potential role of animal behaviour, personality (inter-individual differences that are consistent over time or across contexts) and behavioural syndromes (suites of correlated behaviours) in various fields, such as ecology, evolution, genetics and associated fields, has gained great momentum over the past years and decades. However, the underlying factors influencing their maintenance and evolution has only recently attracted considerable amounts of attention. Especially the potential role of parasites in this context offers a range of interesting unanswered questions worth investigating. This thesis examined the potential impact of parasitic infections on host behaviour and personality from a mechanistic point of view. Thereby, the mechanisms underlying host behavioural change, a phenomenon regularly encountered among wild host species, in a well-established host-parasite model system (the three-spined stickleback (Gasterosteus aculeatus) and the cestode Schistocephalus solidus) were investigated to draw conclusions about the potential role of parasites in the evolution and maintenance of host behaviour and personality. The results showed that the host-parasite interactions in this model system are very complex and to draw unambiguous conclusions, further research is encouraged.