A weakness of exogenous zeitgebers?

-Evidence that challenges the role of exogenous zeitgbers -Miles et al recount the study of a young man, blind from birth, who had abnromal cirrcadian rhythem for 24.9 hours. -Despite exposure ot social cues, like reuglar mealtimes, his sleep/wake cycle could not be adjusted. Signifncant bc it suggests that social alone are not effective in resetting the biological rhythem -However, findings of a case study can't be generalised to a wide population of peopel because it unrepresentative.