We cannot fully rule out a ceiling effect in the E-FAPobstacle subtask results (limiting room for improvement), however comparison of thecurrent HSP data with unpublished control data obtained by us in healthy controls ofsimilar age (N = 15; 49.0 ± 11.5 years) indicated that only 6 of our 36 HSPparticipants completed the E-FAP obstacle subtask within a normal range (mean + 2SDof healthy controls). Here, FAP is linked to hereditary spastic paraplegia.