[mamoswined]

Yeah I wouldn't be surprised if they were a bit more intelligent than jumping spiders through it's hard to judge relative intelligence in animals like these. For mantis shrimp color training probably doesn't resemble anything they encounter in the wild. For jumping spiders, they use colors for sexual selection in most species and also color is a major signal for "poisonous" in their prey — i'm not sure that's the case with mantis shrimp.

[rectangletangle]

You are right, it is difficult to compare intelligence here, because it's predicated on some objective measure of intelligence. It's also difficult because the ways intelligence can manifest can look very different depending on the instance. Perhaps a more general term like "sophisticated" would be appropriate, seeing as they've adapted highly complex responses to a very dynamic and complex environment.

Biology as a field is riddled with these definition based problems, because the phenomena it's used to describe are just so intricate. Another similar problem is the "species problem," where we find countless attempts at an objective and universal definition for differentiating species, but little consensus.

In the case of mantis shrimp it's probably the stimulus being too foreign to the organism for it to have a meaningful response, like you said. So it's probably just ignoring the stimulus until it to goes away.

It may also be the organism's adaptation to an environment with many diverse predators (like a shallow water reef would have). So any unusual stimulus is automatically interpreted as threatening. If they have a tendency to freeze when exposed to acute stress, it may just be their manifestation of the fight-or-flight response. This could probably be measured by comparing nervous system arousal between threatening and foreign stimulus.

[mamoswined]

This is one of my fav papers: How (not) to train your spider: successful and unsuccessful methods for studying learning http://www.tandfonline.com/doi/abs/10.1080/03014223.2015.112...

Because it has all the failed methods for training them that never got published. Some of them are unintentionally hilarious too. > In our laboratory, we also used sprays of water as an aversive stimulus—spiders that moved into one side of an arena received a spray of water. In pilot trials, there was no evidence of learning: spiders ran wildly when sprayed and then stopped to groom themselves. If accidentally sprayed too heavily, they became trapped by the water droplet.

I think more papers like this should exist.