cats

I find that saying something like, "My ears seem to be moving faster than my brain today. Can we try this another time?" is a good way to indicate you're interested in learning what they're saying while acknowledging you're having a hard time comprehending it at that moment.

Most people understand that our brains shut off sometimes; "the lights are on, but nobody's home." Most people also know good and well when someone doesn't understand something. Acknowledging these human traits may be uncomfortable, but it's better than trying to lie to someone who knows better.