higher-frequency spectral peaks, an extremely negatively skewed spectrum, and a longer duration than heterosexual men. However, not all gay American men speak with this hyper-articulated (perhaps fewer than half), and some men who identify as heterosexual also produce this feature. Vowels A 2006 study of gay men in the Upper Midwestern American dialect region found that they tend to lower the vowel (except before a nasal consonant) as well as the vowel. This linguistic phenomenon is normally associated with the California vowel shift and also reported in a study of a gay speaker of California English itself, who strengthened these same features and also fronted the and vowels when speaking with friends more than in other speaking situations. The study suggests that a California regional sound can be employed or intensified by gay American men for stylistic effect, including to evoke a "fun" or "partier" persona. Other characteristics Some other speech features are also stereotyped as markers of gay or bisexual males: carefully enunciated pronunciation, wide pitch range (high and rapidly changing pitch), breathy voice, lengthened fricative sounds, pronunciation of as and as (affrication), etc. Research shows that gay speech characteristics include many of the same characteristics other speakers use when attempting to speak with special carefulness or clarity, including over-articulating and expanding the vowel spaces in the mouth. Perception In terms of perception, the "gay sound" in North American English is popularly presumed to involve the pronunciation of sibilants (, , ) with noticeable assibilation, sibilation, hissing, or stridency. Frontal, dentalized and negatively skewed articulations of (the aforementioned "gay lisp") are indeed found to be the most powerful perceptual indicators to a listener of a male speaker's sexual orientation, with experiments revealing that such articulations are perceived as "gayer-sounding" and "younger-sounding". So even if a speaker does not display all of these patterns, the stereotype of gay speech and the coordination of other non-linguistic factors, e.g. dress, mannerisms, can help form the perception of these accents in speech. Gay speech is also widely stereotyped as resembling women's speech. However, on the basis of phonetics, Benjamin Munson and his colleagues' research has discovered that gay male speech does not simply or categorically imitate female speech. In one Canadian study, listeners correctly identified gay speakers in 62% of cases. A Stanford University experiment analyzed the acoustics of eight males (four straight and four gay), who were recorded reading passages, through the