The Japanese contrastive marker wa can appear within a because-clause as in (1a), while it cannot appear within temporal clauses like toki ‘when’ as in (1b) and if-clauses (omitted for space reasons).
(1) a. Itsumo uchi-ni Mary-wa kuru node kodomo-ga always house-Dat Mary-CTop come because, children-Nom yorokob-u. happy-Present
‘Because Mary
CTop
always comes to our house, the children are happy.’
b. *Itsumo uchi-ni Mary-wa kuru toki, keeki-o motteku-ru. always house-Dat Mary-CTop come when, cake-Acc bring-Present ‘When Mary
CTop
comes to our house, she always brings a cake.
Interestingly, the same asymmetry is found with an evidential morpheme.
(2) a. Kodomo-ga kuru sounanode, oyatsu-o youi-shita. children-Nom come Evid because, sweets-Acc preparation-di ‘Because I heard that children are coming,
I prepared sweets.’
b. * Kodomo-ga kuru sounatoki, oyatsu-o youi-shita. children-Nom come Evid when, sweets-Acc preparation-did ‘When I heard that children are coming, I prepared
sweets.’