Ah yes. That's right. I also remember we talked about the case of permanent magnets and objects suspended above them. I don't remember what his answer was and I wouldn't be surprised if he told me to try to work it out for myself because my questions were holding the class up.

Work can turn out to be one of the less intuitive aspects of physics. For example, magnetic fields cannot do any work because they act orthogonally to the direction of motion, yet it certainly looks like work when you use an electromagnet to lift an object and make it float. I wish I could remember the explanation my Electromagnetism professor gave me for what is actually doing the work in that scenario.

Likely not solely to do with spiders, but we have an actual in-built ability to rapidly identify things like spiders in our environment. It's a phenomenon pretty specific to spiders and snakes. Here's a phys.org article from 2015 on our predisposition: https://phys.org/news/2015-04-human-spiders-scientific-focus.html

It is present very early on; as early as a few months old. This study found that presenting 5-month-old babies with pictures of shapes in 3 different configurations, one of which was a spider, resulted in the child focusing on the spider above other images.

Here's another article that talks about it. https://www.fatherly.com/health-science/when-do-babies-develop-fear-of-heights-snakes-and-spiders

Note: There's no evidence of an instinctual fear response; just the tendency to identify and fixate on spider and snake images. Still, the ability to identify them in our environment probably relates to survival; individuals that had that ability were more likely to survive and procreate.