Is there a way in Clojure to test a vector and see if it's nested, i.e. a way to test [:a :b :c :d] vs. [[:a :b] [:c :d]]?

I've tried the test 

```
(vector? [:a :b :c :d])
 true

```

but it remains true for nested vectors as well,

```
(vector? [[:a :b] [:c :d]])
 true

```