METHOD AND APPARATUS FOR
ESTIMATING FITNESS TO PERFORM
TASKS BASED ON LINGUISTIC AND
OTHER ASPECTS OF SPOKEN RESPONSES
IN CONSTRAINED INTERACTIONS 5
This application is a continuation-in-part of U.S. application Ser. No. 08/753,580, entitled Method and Apparatus For Combining Information From Speech Signals for Adaptive Interaction in Teaching and Testing, filed Nov. 25,1996 by Jared C. Bernstein now U.S. Pat. No. 5,870,709, issued Feb. 9, 1999.
FIELD OF THE INVENTION 15
The area of the present invention relates generally to voice-interactive systems using speech recognition and, more particularly, to such systems which track the linguistic, indexical and/or paralinguistic characteristics of spoken 20 inputs to estimate the suitability or fitness of a user to perform employment duties or tasks.
Many computer systems support a function whereby a human user may exert control over the system through spoken language. These systems often perform speech recognition with reference to a language model that includes a rejection path for utterances that are beyond the scope of the application as designed. The speech recognition component of the application, therefore, either returns the best match within the language model designed for the application, or it rejects the speech signal. A good description of a variety of systems which incorporate such methods can be found in "Readings in Speech Recognition," edited by Alex Waibel and Kai-Fu Lee (1990).
Computer assisted language learning (CALL) systems for second language instruction have been improved by the introduction of speech recognition. Bernstein & Franco, 4Q ("Speech Recognition by Computer," Principles of Experimental Phonetics, Ch. 11, pp. 408-434, 1996) and the references therein show some examples. In most cases, the speech recognition component of the CALL system has been used as best match (with rejection) or as a scored perfor- 45 mance for testing and skill refinement, either for nonnative speakers of the target language or for hearing-impaired speakers.
Prior laboratory demonstration systems have been designed to offer instruction in reading in the user's native 50 language. Two systems have emulated selected aspects of the interaction of a reading instructor while the human user reads a displayed text aloud. One system based its spoken displays on the running average of poor pronunciations by the reader (see, e.g., WO 94/20952 by Rtischev, Bernstein, 55 and Chen), and the other system developed models of common false starts, and based its spoken displays on the recognition of the occurrence of these linguistic elements. (See J. Mostow et al., "A Prototype Reading Coach that Listens," Proc. 12th Nat. Conf. Artificial Intelligence, AAAI- go 94, pp. 785-792, 1994).
Expert teachers and other human interlocutors are sensitive not only to the linguistic content of a person's speech, but to other apparent characteristics of the speaker and the speech signal. The prior art includes systems that respond 65 differentially depending on the linguistic content of speech signals. Prior art systems have also extracted indexical
information like speaker identity or speaker gender, and calculated pronunciation scores or speaking rates in reading. However, these extra-linguistic elements of human speech signals have not been used in combination with the linguistic content to estimate the speaking proficiency or other characteristics of a human user. Measurement of extra-linguistic aspects of a user's speech along with the linguistic content of the speech allows finer estimation of the human user's skill state and the user's psychological state. Finer estimation of skills or states facilitates more exact control of the operation of the computer system in a manner appropriate to the skill state of the human user and the current state of readiness of the user. Such control of computer-based graphic and audio displays is useful and desirable in order to facilitate fine-grained adaptation to cognitive, verbal and physical skill state of the human user.
In the U.S. Pat. No. 5,870,709 of U.S. application Ser. No. 08/753,580, it was shown how computer systems that interact with human users via spoken language may be improved by the combined use of linguistic and extra-linguistic information manifest in the speech of the human user. It is also known that an individual's psychological state impacts aspects of that individual's speech. For example, it has been determined that mean fundamental frequency and other extra-linguistic speech characteristics can be markers of a speaker's emotions. See, e.g., Stassen H H, Bomben G, Gunther E. Speech characteristics in depression. Psychopathology, 24:88-105, (1991).
Using such knowledge, and recognizing that other speech characteristics are considered to be important in the analysis of emotion from speech, others have proposed methods for using these speech characteristics in self-training biofeedback systems. See, e.g., U.S. Pat. No. 5,647,834. However, to date such system have relied on measures from open speaking to estimate a user's psychological state.
SUMMARY OF THE INVENTION
In one embodiment, the present invention provides a computer-assisted method that involves determining a user's fitness for a particular task based, at least in part, on one or more measures estimated from one or more spoke n responses received from the user in response to one or more prompts. Importantly, the prompts are chosen on the basis that they can be expected to elicit responses characterized by low linguistic entropy. For example, the prompts may be requests for information; requests to draw an inference; requests to read a linguistic unit; requests to repeat or paraphrase a linguistic unit; or requests to complete, fill in or identify a verbal or graphic aggregate. The measures may be linguistic and/or extra-linguistic measures. The user's fitness for the particular task may then be estimated with reference to selected constructs required for the performance of the particular task. For example, psychomotor, perceptual, cognitive and/or emotional constructs may be used.
The user's spoken responses may be received at an interactive computer system via telephone or other telecommunication or data information network. Depending on the particular system, the prompts may be graphical prompts, audio prompts, or a combination of verbal and graphical elements.
In addition to the above, the prompts may be further chosen based, at least in part, on one or more extra-linguistic and/or linguistic measures estimated from the one or more spoken responses.
In another embodiment, a computer-assisted method involves estimating states of a user from measures derived