In sequence-space synaesthesia, members of linguistic sequences such as numbers, days of the week and letters of the alphabet are perceived to occupy spatial positions, either in the mind's eye or as locations in space around the body. In this chapter, we begin by considering the possible sequences that can induce this type of synaesthesia, with the focus on numbers, time-units and letters. We evaluate the various methods used to test the genuineness of self-reports of this type of synaesthesia, and (...) we make suggestions for novel techniques that could address the shortcomings of the current methods. Lastly, we briefly outline the current theories on the neural basis of this type of synaesthesia, including the recent reification hypothesis. We conclude by discussing how scientific findings with sequence-space synaesthetes can be beneficial for the study of cognitive psychology more generally. (shrink)