The term stopping is most often used to refer to a feature of child phonology. Most children go through a phase, which can persist into the early school-age years, when sounds with an open articulation, usually fricatives, but also sometimes approximants, are replaced by homorganic or near-homorganic stops. A good example is the pronunciation ˈtɪdəd for adult scissors. The voicing of the target consonant is usually preserved.
I have known for a long time that stopping can also occur in adult speech, but have only just now started wondering how widespread it is. The two examples I have both come from speakers in Texas and they are isn’t pronounced as ˈɪdn and wasn’t pronounced as ˈwɑdn.
As I said, I don’t know if this is confined to Texas, or if it is more widespread in the USA, or if it occurs in other accents of English. Does anyone have information on this?
Update 2013_09_20 I have just come across this Youtube clip
The speaker is from Louisiana. At about 0:48 he says: “it dədnt have the same tenseness”.