Spanish speakers seem to habitually use the imperfect tense for "deber" where English speakers would use the past tense, e.g.,
"Paul owed her his life" => "Pablo le debía la vida" instead of "Pablo le debió la vida"
"You guys must've figured something out" => "Debíais haber descubierto algo" instead of "Debisteis haber haber descubierto algo"
... and sometimes where English speakers would use the present tense, e.g., "But the Lord said he must go to Ninevah" => "Pero el Señor insistió en que debía ir a Nínive" instead of "Pero el Señor insistió en que debe ir a Nínive."
They also use the imperfect in situations that seem to call for a past-tense conditional ("should have"):
Si querías baile, debías haber recurrido a mí => If you wanted dancing, you should have come to me
I would have expected "Si querías baile, deberías haber recurrido a mí" (should have). Sometimes I do see "deberías haber" for "should have", and I can't see any pattern to why one is chosen instead of the other.
In some cases, the imperfect is used where the present-tense conditional seems clearly called for, e.g., "debias esperar hasta que llamara" for "you should wait until he calls." There's nothing past-tense-ish about that sentence.
"deberían" ('they should") in particular is used interchangeably with "debían" (literally "in the past they must"), and neither is used for past-tense "they should have".
Can someone explain how Spanish speakers conceptualize these tenses of "deber"? Does the choice of tense work the same way for "deber" as "owe" and "deber" as "must", or are they treated differently?
