etiquette - Should I include funny pictures in my slides?

I am preparing slides for a short (10min) talk at the group meeting. The talk is about a fairly serious piece of (pure) mathematics, and it so happens that there is a very relevant one-panel webcomic. A thought appeared to me, and got some support from my fellow PhD students, that it would be cool to include this comic, perhaps at the final thank-you-for-your-attention slide.

I am probably not going to do it, so I'm asking mostly out of curiousity: Would this be a bad idea to go ahead and include a comic on the final slide?

Note: The comic is genuinely funny (based on a sample of 6 non-randomly selected students). It is not - as far as I can tell - offensive in any way. It could come across as somewhat silly.

Answer

Human cognition is a strange thing, and I won't pretend I know it well enough to give you a guide, but I will suggest that you simply consider your audience and how you want them to move through the information.

A dense, heavy talk with few breaks will tire most audiences.

A light talk that doesn't require much thought will result in many people letting their mind wander.

A talk which carefully weaves the "story" with a variety of dense to light moments, may actually improve retention.

Adding levity in the form of a joke or humor, if the joke is very relevant to the talk, can actually increase retention, as long as it isn't too much of a distraction. Placing it appropriately is key, though, and I wouldn't do it at the end, because that's what people will remember. The last few sentences should be a quick summary of the talk and should be memorable.

Placing it in the middle, during a transition - for instance between the problem statement and the methodology - could be good, and allow a release of tension if the problem statement was pretty densely packed.

Starting off with it, as an into to the topic and a method to get attention is also a pretty good choice.

In all things, though, consider your audience first. What is the journey you are taking them on, and when would be an appropriate point for a rest break, a transition, a wake-up, etc.