I remember reading a study several years back that suggested that the comparative legibility of serif vs. sans serif type was based more on the age of the reader than on his or her country of origin. The study concluded that older readers found serif type more legible because that's what they grew up reading; younger readers found sans serifs more legible.

As best I can recall, the study is now more than thirty years old. I am fairly confident that the conclusions are still reasonably valid, but with a twist. The range of typefaces available now has expanded public awareness of the tremendous range of possibilities for expressing individual letterforms, so what is legible to the younger reader of today might well seem like hieroglyphics to his or her grandparents.

But we're talking about signage here, and good signs aren't intended to be works of art, but rather useful tools, and really shouldn't require decipherment. Probably the best test of the utility of a typeface used for signage is that individual letterforms be unambiguous. If they pass that test, all other design considerations are superfluous.

Research has been done on both country of origin and age. My poor memory doesn't have the details (perhaps it was the Royal College?). From what I remember of the conclusions it seems countries like England and the U.S. were more prone to read serif; countries like Germany and Switzerland were more prone to read sans better. This fits Nick's "what they grew up reading" theory as well.
I have not seen a book that compares a large crossection of legibility literature since Rolf Rehe's 1972 book "Typography How to Make it Most Legible". This book still did not satisfy my curiosity then and very much has happened since. The "Typo" readability issue http://www.magtypo.cz/english.html was a good beginning but I still have not seen work that gets at the whole problem enough to be practical. There has been far more research done in signage mostly by engineers.

ChrisL

I am surprised Chris' original post didn't stir more discussion. Thanks for reviving the topic, Terry.

Chris asks a lot of questions, inadvertently revealing the state of legibility 'science' in the process. We really don't have any definitive answers to most of those questions yet.

I maintain that any serious inquiry will require a long gestation period, sufficient funding, and input from a variety of experts, most crucially typographers. It might help to narrow the question down a lot. This is presumably what would be done in lab testing. Suppose we say we are discussing text typefaces designed for immersive reading, as in books? That helps us avoid distractions about display type, signs, glare, children, etc. and lets us focus on immersive reading issues like comfort, speed, etc. But Terry's project pertains to signage. So maybe we should narrow it down to wayfinding typefaces for particular environments, i.e. large metropolitan transit systems. That would take us someplace very different from the discussion/study of ideal book faces.

Terry, how would you like to frame the discussion? It's clear that these areas overlap, but you may get farther if the topic is more specific. I'm all for starting 2 threads: 'Optimal Signage Legibility Fonts' and 'Optimal Book Legibility Faces', if not more.

"inadvertently revealing the state of legibility ‘science’ in the process."

Perhaps not so inadvertently :-)

ChrisL

Hmmmm, Carl...maybe there should be two threads on this. I'll go ahead and start the signage one. I am also interested in the legibility for reading because I wonder if the two overlap.

Actually...I did start a thread similar to that a while back, with very little response. Environmental design doesn't seem to be too terribly popular here.

Deliberative and immersive reading are like two vectors at a 90-degree angle.

hhp

"Deliberative and immersive reading are like two vectors at a 90-degree angle."

Some would disagree. I myself don't know whether I agree or disagree, because there hasn't been enough proof supporting either side of the argument.

Do you have proof you're not going to get run over by a car when you leave the house? Ideally, we do what we feel we should - balancing everything, pragmatically.

But you're certainly right that people disagree a lot on this stuff. Some type designers -including famous ones with enviable sales and awards- even maintain that there's no essential difference between display and text type.

hhp

Signage is different than display type. We add all sorts of distractions and reading distances as well as movement and viewing angle to the equation. Perceptual Psychologists tend to do more research in the signage arena. There is more research money there.

ChrisL