This study investigated the extent to which language familiarity affects the perception of the indexical properties of speech by testing listeners' identification and discrimination of bilingual talkers across two different languages. In one experiment, listeners were trained to identify bilingual talkers speaking in only one language and were then tested on their ability to identify the same talkers speaking in another language. In the second experiment, listeners discriminated between bilingual talkers across languages in an AX discrimination paradigm. The results of these experiments indicate that there is sufficient language-independent indexical information in speech for listeners to generalize knowledge of talkers' voices across languages and to successfully discriminate between bilingual talkers regardless of the language they are speaking. However, the results of these studies also revealed that listeners do not solely rely on language-independent information when performing these tasks. Listeners use language-dependent indexical cues to identify talkers who are speaking a familiar language. Moreover, the tendency to perceive two talkers as the "same" or "different" depends on whether the talkers are speaking in the same language. The combined results of these experiments thus suggest that indexical processing relies on both language-dependent and language-independent information in the speech signal.

Previous research has shown that familiarity with a talker's voice can improve linguistic processing (herein, "Familiar Talker Advantage"), but this benefit is constrained by the context in which the talker's voice is familiar. The current study examined how familiarity affects intelligibility by manipulating the type of talker information available to listeners. One group of listeners learned to identify bilingual talkers' voices from English words, where they learned language-specific talker information. A second group of listeners learned the same talkers from German words, and thus only learned language-independent talker information. After voice training, both groups of listeners completed a word recognition task with English words produced by both familiar and unfamiliar talkers. Results revealed that English-trained listeners perceived more phonemes correct for familiar than unfamiliar talkers, while German-trained listeners did not show improved intelligibility for familiar talkers. The absence of a processing advantage in speech intelligibility for the Germantrained listeners demonstrates limitations on the Familiar Talker Advantage, which crucially depends on the language context in which the talkers' voices were learned; knowledge of how a talker produces linguistically relevant contrasts in a particular language is necessary to increase speech intelligibility for words produced by familiar talkers.

Phonologists have long discussed the properties of 'stress' in Turkish, though there are some authors that suggest that Turkish is actually a pitch-accent language. As a first step in determining whether Turkish should be grouped with pitch-accent languages such as Basque and Japanese or with stress-accent languages such as English, this experimental study provides a detailed phonetic examination of word-level accent in Turkish. Seven female native speakers of Turkish were recorded saying 40 target words in three repetitions. The results show that there are significant differences in duration, peak amplitude, and peak F0 between words with final vs. non-final lexical accent. The magnitude of the duration differences, however, is not likely to be sufficiently perceptible to be a reliable cue to accent placement. The F0 peaks were dramatically different between lexically accented and unaccented syllables. A discriminant analysis confirms that F0 is the most robust cue, followed by intensity and then duration. The current study also provides a method for determining lexical accent placement in words where accent placement has been disputed. That is, a marked drop in F0 signals that the syllable preceding the drop contains the lexical accent.

A bilingual advantage has been found in both cognitive and social tasks. In the current study, we examine whether there is a bilingual advantage in how children process information about who is talking (talker-voice information). Younger and older groups of monolingual and bilingual children completed the following talker-voice tasks with bilingual speakers: a discrimination task in English and German (an unfamiliar language), and a talker-voice learning task in which they learned to identify the voices of three unfamiliar speakers in English. Results revealed effects of age and bilingual status. Across the tasks, older children performed better than younger children and bilingual children performed better than monolingual children. Improved talker-voice processing by the bilingual children suggests that a bilingual advantage exists in a social aspect of speech perception, where the focus is not on processing the linguistic information in the signal, but instead on processing information about who is talking.