Here's the sentence that's been confusing me:

Compared to dogs, cats shows more enthusiasm.

I feel this should be a complex sentence because there's one independent clause and one dependent clause. But there is no subordinating conjunction here.

Now consider

When compared to dogs, cats showed more enthusiasm.

This one fits the definition of a complex sentence (independent clause, dependent clause, and a subordinating conjunction "when").

My question is this: how to detect complex sentences of the former type?

Here's the sentence that's been confusing me:

Compared to dogs, cats showed more enthusiasm.

I feel this should be a complex sentence because there's one independent clause and one dependent clause. But there is no subordinating conjunction here.

Now consider

When compared to dogs, cats showed more enthusiasm.

This one fits the definition of a complex sentence (independent clause, dependent clause, and a subordinating conjunction "when").

My question is this: how to detect complex sentences of the former type?