Spider intelligence?

Here's an interesting question. How intelligent is a spider?
Are they just irritating beasts?
Now, obviously, I KNOW they aren't. But I may have just recently conducted a fascinating experiment purely by accident.
About a year ago, perhaps even longer ago, a spider set up camp in my bathroom window. A humble little amaurobius similis.
I wasn't bothered by him/her. And so, this relationship continued for months. It just sat there on the window ledge every day. Regardless of whether I was using the loo, cleaning my teeth, or just having a shower. It was always in the same position. Never bothered it and it never bothered me.
Now, you can call me cruel, or maybe experimental, but about two weeks ago, a smallish tegenaria spider (domestica - too small to be duellica or gigantea) crawled across my sofa. I grabbed him in a beaker and popped him on the windowsill in my bathroom. The amaurobius similis did what I can only describe as packed his bags. At the point I dropped the larger spider, the little amaurobious tried to attack, backed off and disappeared. Then, for days, the tegenaria spider actually sat guarding the web I'd dropped it in, belonging, in fact to the amaurobius similis.
Then I felt very guilty. This little spider had been there for a year. I even had a holiday abroad and came back to see the little fella sat there.
Then, bizarrely, this week, the very same amaurobius similis started appearing around my flat. Obviously looking for warmth or food. Tonight I went to the windowsill, checked the web, found the tegenaria (yes, it was still there - thinking 'cheers mate, you gave me free food here when you dropped me here) removed it and put it outside.
I then found the amaurobius similis, caught it in my hand, left it on the bathroom wall, and, I HAVE to report, it has taken up its usual residence in the silk it laid in my bathroom window frame.

Spiders. They don't give them eight legs for nothing!
Stay webwise folks.

xx Gav.