A: I thought there was a zoo in the city centre.
B: I thought that, but apparantly there isn’t.
I always just say “Ich habe das gedacht”, but I heard that it should be “Ich habe daran gedacht”. What’s the difference and what’s the most common German way of saying it?
Also, is “Ich habe das gefunden” not in the sense of literally finding something but more like “I found, that it's more difficult to do that now”?
The question boils down to which verbal expression you’re using. Denken has two possible extensions: etwas denken or an etwas denken. With demonstrative pronouns, these two expressions become:
Ich habe das gedacht.
or
Ich habe daran gedacht.
Etwas denken translates pretty well to to think something, where something is typically a subordinate clause of some sort. Like in your first example sentence which would translate to:
Ich habe gedacht, dass es in der Stadtmitte einen Zoo gibt.
An etwas denken typically translates to to think about something, typically a noun. So you could build a sentence:
Ich habe an den Zoo gedacht.
Your question obviously asks for the first of these two constructions. If you transform the subordinate clause into a pronoun, that pronoun has to become a simple das.
Ich habe das gedacht.
If you want to replace an den Zoo from the second sentence by a pronoun, that one needs to be daran — or an das in very informal, colloquial usage. Stick with daran, though.
Ich habe daran gedacht.
Idiomacity is a bit tricky in this case, since thinking about something is so much more common than merely thinking something. Hence why somebody probably thought you wanted to say the other thing. But if you were referring to a thought as present in a subordinate clause, it has to be das, no other options.
The same thing is true about finden, except that there is no *an etwas finden, and that the figurative meaning of the verb overlaps with the literal one. As such, I would deem a sentence with finden in your second example to be not quite as idiomatic, since the second meaning can unintentionally shine through. Instead, I would propose the following for ‘I find that it’s more difficult to do that now’:
Ich stelle fest, dass es jetzt schwerer ist, das zu tun. → Ich stelle das fest.
And for ‘I found that we had little in common’:
Ich habe gemerkt, dass wir wenig gemein haben. → Ich habe das gemerkt.[1]
But if context is clear enough, you can use the verb finden as intended by you:
A: Ich finde, dass dein Chef ein netter Mensch ist.
B: Das finde ich auch.
(Word order changed from ‘Ich finde das auch’, because this emphasised version sounds more natural here.)
[1]: Please credit Danni’s answer for the word choice here.
As a native speaker, I would translate your example sentences the following:
A: Ich dachte, es gäbe einen Zoo im Stadtzentrum.
B: Das dachte ich auch, aber offensichtlich gibt es keinen.
and:
I found that we had little in common.
Ich habe gemerkt, dass wir wenig gemeinsam hatten.
You say
Ich habe das gedacht
mostly when there is an alternative to choose from, and you say
Ich habe daran gedacht
when you remembered something or when you ponder something.
Examples:
Wusstest du, dass der schnellste Weg mit der U-Bahn ist? -- Nein, ich hatte gedacht, dass das Taxi schneller sei. (Das hatte ich gedacht.)
Ist das Wasser abgestellt? -- Ja, daran habe ich gedacht.
Hast du schon etwas von japanischem Theater gehört? -- Ja, ich habe daran gedacht, dass wir einmal nach Japan fliegen um dort eine Vorstellung im Original zu sehen.
Please note that
Ich habe das gedacht
cannot stand as a sentence of its own, while
Ich habe daran gedacht
can -- as an answer to a question, see example two above.
A similar word to use (although not such frequent in colloquial speech) is "bedacht" meaning "think of".
Hast du bedacht, dass unsere Reise viel Geld kostet?
Which is preferrable to
Hast du gedacht, dass unsere Reise viel Geld kostet?
which would mean "did you imagine our voyage being expensive" with a bit of a hint to an expected answer "no".
Da- compounds like "daran" are used when combining a preposition with a reference to something you were talking about earlier: https://courses.dcs.wisc.edu/wp/readinggerman/category/12-da-compounds/
"Denken" is often combined with the preposition "an": "an etwas denken" means "to think about something". Therefore "Ich habe daran gedacht" is commonly used to say "I was thinking about it". You need to use "daran" instead of "das" when you want to express that you were thinking about something.
However, in your example I think @Danni is right, it makes more sense not to use the "an" preposition but simply say "Das dachte ich auch".
The verb "finden", as in English, can be used both literally and figuratively. Was that your second question?
