Can anyone say why in many cultures, 7 is a magic number, and, does the 7 mean something to you?

I read somewhere once that 7 of a group on alike objects was the last amount your brain recognises as even or odd at a glance without having to count how many of the thing there are. The writer used a bunch of flowers as an example explaining how a bouquet of even numbered flowers just looks "wrong" until there are more than seven after which we just see "a bouquet" of flowers.

Maybe reading that made me "see" things differently, but I've found this to be true. Seven seems to be a primitive hardwired limit to a type of cognition, so it's not surprising that so many cultures have seen it as meaningful.

I have a mild form of synesthesia. Seven is only significant to me insofar as it's a warm shade of orange and quite friendly whereas eight and nine are drab blue bullies. Seven would rather be elsewhere on a number line. Try explaining that to a primary school teacher before you learned that other people didn't see numbers and letters the same way as you!