Abstract
Fractal dimensions and characteristic periodicities were evaluated in normal sentences, computer-generated word salads, and word salads from schizophrenia patients, in both Japanese and English, using the random walk patterns of vowels. In normal sentences, the walking curves were smooth with gentle undulations, whereas computer-generated word salads were rugged with mechanical repetitions, and word salads from patients with schizophrenia were unreasonably winding with meaningless repetitive patterns or even artistic cohesion. These tendencies were similar in both languages. Fractal dimensions between normal sentences and word salads of schizophrenia were significantly different in Japanese [1.19 ± 0.09 (n = 90) and 1.15 ± 0.08 (n = 45), respectively] and English [1.20 ± 0.08 (n = 91), and 1.16 ± 0.08 (n = 42)] (p < 0.05 for both). Differences in long-range (>10) periodicities between normal sentences and word salads from schizophrenia patients were predominantly observed at 25.6 (p < 0.01) in Japanese and 10.7 (p < 0.01) in English. The differences in fractal dimension and characteristic periodicities of relatively long-range (>10) presented here are sensitive to discriminate between schizophrenia and healthy mental state, and could be implemented in social robots to assess the mental state of people in care.
Highlights
Language is generally regarded as a one-dimensional array working in a multidimensional space where characters interact with each other, from short to long-range, resulting in the formation of particular patterns, such as words and sentences
In normal conversations (NJ and normal conversations in English (NE)), the curves were smooth with gentle undulations, whereas in computer-generated word salads (CJ and computer generated word salad (CE)), they were rugged with mechanical repetitions
These methods are essentially independent of the meaning of the written or spoken word, and the relevant algorithms presented in the present study could be implemented in social robots to assess the mental state of a person in care
Summary
Language is generally regarded as a one-dimensional array working in a multidimensional space where characters interact with each other, from short to long-range, resulting in the formation of particular patterns, such as words and sentences. Such patterns typically represent meaning, and include human thoughts, feelings, emotions, will, and knowledge. Words are generated by choosing an appropriate word from multiple synonyms that possess various nuances (homonymy or polysemy) [1,2,3,4,5], and during that selection, the acoustic or sound image of signs is referred to. The interference between the sound image and the meaning discriminates the natural language from programming language or mathematical language.
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