My roadie has brifters (Shimano 105) but my commuter has Tiagra which has brifters with thumb levers. We went out to do a long ride one day after I had been riding my commuter a lot and I panicked and told DH "OH NO!!! My shifter is broken, the lever broke off!!" I was looking for the non-existent thumb lever. And I often have to remind myself which one I am on to remember. I am 27.