When do I need to use the indirect object pronoun?
Do I always need to use the indirect object pronoun or only when the indirect subject is not specified in the sentence. for example which is correct:
El profesor le dijo al alumno que la respuesta era correcta.
El profesor dijo al alumno que la respuesta era correcta.
¡Gracias!
4 Answers
Unlike the IOP, you cannot have a DOP together with the DO to which it refers.
Actually, you have to when the DO precedes the verb.
If I wanted to "shorten" the phrase, "El profesor le dijo al alumno que la respuesta era correcta" by using only the IO and the DO, could I say. El profesor se la dijo que era correcta.
No. If you wanted to only use the IOP and DOP, you would say:
El profesor se lo dijo.
The "lo" is the DOP referring to "que la respuesta era correcta". Unlike the IOP, you cannot have a DOP together with precede the DO to which it refers.
The "se" is a spelling change for "le", which is the IOP for "el alumno". We change the spelling because "le lo" sounds weird. 
Therefore, you would need "le" or whatever indirect object pronoun is suitable for the IO.
Exactly. You always say the i.o.p. even when the i.o. is explicitly mentioned
I have to disagree slightly with these assertions.
It would probably be best to say that this is "most often" the case, but I would be hesitant to claim that it is "always so."
The indirect object pronoun need not be stated in all instances that an indirect object appears in a sentence, a fact which can be attested to by the following newspaper quotes:
?La víctima dijo a la policía que por la tarde, fue interceptado por un sujeto que a la fuerza lo subió a su camioneta y lo llevó al Motel "La Herradura"
?El presidente Ollanta Humala Tasso rompió hoy su silencio a su llegada a Pisco, donde aseguró a los damnificados del terremoto del 2007 que su prioridad será la reconstrucción de la ciudad.
?El presidente de Venezuela Hugo Chávez agradeció a Rusia el robustecimiento de la capacidad combativa de las FFAA del país suramericano.
?“Los cómics gustan a la gente. Yo no soy tan fanático, pero sí me llaman mucho la atención, por eso vengo y también para salir de la rutina y aprender más de técnicas para hacer cómics, jugar cartas y poder intercambiarlas”
The rule, at least according to the DPD (See 5. Duplicación de complementos: coaparición del clítico y el complemento tónico—especially 5a and 5b), is that the (atonic) indirect object pronoun is optional if the indirect object appears after the verb as a noun phrase (introduced by the preposition "a," of course).
On the other hand, the indirect object pronoun is obligatory in all cases where it is accompanied by a prepositional pronoun. This might best be understood by noting the difference in the following examples:
Indirect Object Pronoun ? Optional
Kirchner (le) agradeció el apoyo a Chávez (Kirchner thanked Chávez for his help.)
The I.O. appears after the verb as a noun phrase introduced by the preposition "a." Because it appears after the verb, the indirect object pronoun "le" is optional.
Indirect Object Pronoun ? Mandatory
A Chávez le agradeció el apoyo. (He thanked Chávez for his help.)
The indirect object appears before the verb as a noun phrase introduced by the preposition "a." Because it appears before the verb, the indirect object pronoun "le" is mandatory.
(1). A él le agradeció el apoyo. (He thanked him for his help.)
(2). Le agradeció el apoyo a él. (He thanked him for his help.)
In both cases above, the indirect object appears as a prepositional pronoun; therefore, the indirect object pronoun "le" is mandatory.
The first one is correct.
If you have "...a la maestra", or something along those lines, it's a good indicator that that is likely the indirect object. Therefore, you would need "le" or whatever indirect object pronoun is suitable for the IO.
"I told my cousins about the test."
"Les dije a mis primos del examen."
