Factors to be considered in speech processing:
Serial versus parallel processing (ie, whether processes are carried out sequentially or processes occur simultaneously).
Ascending vs. descending processes (representations about basic or fundamental characteristics or parameters of the (Vs, representations of related characteristics).
Automatic vs. controlled processes (not only do they differ in conscious control or speed, but other factors such as learning, flexibility, interference, etc.) need to be taken into account.
3 major problems that should explain theories of speech perception:
Co-articulatory speech demands: When pronouncing a sequence of phonemes, each phoneme is not articulated separately, but the articulatory organs adjust their position to produce the anterior and posterior phoneme, that is, the phoneme production / n / depends on the other phonemes accompany it. The concept of co-articulatory speech demand is the source of segmentation problems, of absence of invariance; of the indissociable presence in the speech of acoustic characteristics as fundamental frequency that establishes the tone of vos and the intensity of the speech, and that the perception of the speech remains intact even when there is a loss of acoustic information by effect of the noise.
Absence of invariance: Lack of correspondence between acoustic signal fragments and phonemes. The speech segments are continuous, influenced by the acoustic context. They lack invariant properties, yet the listeners capture the perceptual constants and identify the sounds. That is, the physical signal does not have the same characteristics for the same phonemes, depending on the context the signals are different, although the listener identifies the same phoneme.
Absence of segmentation: The speech signal is continuous, while the speech sounds are perceived as discontinuous, for example, if in a syllable we separate the fragment of the consonant spectrum from the vocal spectrum and present the subject only the part of the Consonant, he is able to guess the vowel.
These problems lead to the need to recognize different levels of processing:
Auditory level (represents the signal according to its attributes of frequency, intensity and time).
Phonetic level (recognition of sounds by a combination of acoustic signals, such as formant transitions).
Phonological level (the phonetic segment becomes a phoneme applying phonological rules to the sequence of sounds). These three levels can be interpreted as successive discriminations applied to the signal.
Modularity: In relation to a principle of functional specialization is studied if the processing of the language constitutes a modular system. See characteristics of the modular systems exposed by Fodor in 1983.
We also study the relations of the processes of the perception of the speech with the rest of processes carried out in the language.
Theory of categorical perception (Liberman, Harris, Hoffman and Griffith, 1957)
It indicates that responses to verbal stimuli occur in absolute terms even when the stimuli themselves can vary continuously, and indeed vary, in some gradual way.
While this theory is not one of the most supportive of today, categorical perception has developed a lot and can be considered a research paradigm. A good article on categorical perception:
Speech perception motor theory (Liberman et al., 1967) speech perception is produced by reference to production, that is, that listeners use their implicit articulatory knowledge, knowledge about how sounds are produced.
Interactive Activation Model (McClelland and Rumelhart, 1981) Based on previous efforts (Adams, 1979; Johnston and McClelland, 1980; Morton, 1969). Model mainly focused on word, applied to written or spoken. It is based on the fact that the processing takes place simultaneously and with interaction of the three levels: traits, letters and words. Inhibitory, inhibitory and excitatory and inhibitory levels. It is the beginning of interactive and connectionist models.
In general the connectionist models accept influence of the syntactic and semantic context.
Source: Carroll, David, W. (1999). Psychology of Language. Pacific Grove: Brooks/Cole Publishing.
There are many theories and studies on the perception of speech, it is a very developed and complex field, I hope to reflect basic questions to facilitate a field of study for any theory. I believe that the book on which I base provides a great basis for studying later any theory, study, etc.