Pensar sobre

Question

Hi Inma, I read your response below to Anna’s question “en vs sobre” and noted that there are three more examples of the use of “sobre” in the lesson.

¿Qué pensáis vosotros sobre este tema?

Nosotros pensamos sobre la situación política del país.

¿Qué piensan ustedes sobre esta candidata?

It seems to me, as you indicate in your response below, that “pensar sobre” es associated with an opinion, but I’m not sure about the details.

“Qué + pensar + sobre” seems to be a construction to ask for an opinion, the same as we would in English. “What do you think about…”

I’m not sure about the example that begins with “Nosotros pensamos sobre…” but it seems to indicate that they are forming an opinion.

Is this correct? Thanks.

Answer

Hola Marcos
To me, personally, the use of the preposition sobre with pensar is very limited. In those examples in the lesson that you also mentioned I can see a "seeking for an opinion" type of question, so, these make sense to me, although I would have preferred to use "de", but this could be just a personal choice: 
 ¿Qué pensáis vosotros de/sobre este tema?  
 ¿Qué piensan ustedes de/sobre esta candidata? 
In this other sentence, you can use "sobre" despite not being an opinion but a reflection on a specific theme:
Nosotros pensamos sobre la situación política del país.
It sounds a bit unnatural to me (because it's using the verb in the simple present, but I understand why, the lesson is all about pensar in the present tense) - for me this would sound much better as: "Estamos pensando EN la situación política del país." 
I'm not sure about the specific nuance of sobre with pensar as opposed to the other prepositions. I tried to find sentences with pensar, but most of them come up with en and de as I said. If you look here for example you don't have any example using sobre. In the examples that RAE offers for the verb pensar, these don't use sobre at all - it's definitely a less preferred preposition with pensar.
Maybe when using sobre it's more of a deep thought, but I'm not sure. 
Sorry not to offer more clarification. It's one of those where it's very difficult to see the specific nuance, if any. 
Saludos