The maturation of speech structure in psychosis is resistant to formal education

Abstract

Discourse varies widely with age, level of education, and psychiatric state. Word graphs have been recently shown to provide behavioral markers of formal thought disorders in psychosis (e.g., disorganized flow of ideas) and to track literacy acquisition in children with typical development. Here we report that a graph-theoretical computational analysis of verbal reports from subjects spanning 6 decades of age and 2 decades of education reveals asymptotic changes over time that depend more on education than age. In typical subjects, short-range recurrence and lexical diversity stabilize after elementary school, whereas graph size and long-range recurrence only steady after high school. Short-range recurrence decreases towards random levels, while lexical diversity, long-range recurrence, and graph size increase away from near-randomness towards a plateau in educated adults. Subjects with psychosis do not show similar dynamics, presenting at adulthood a children-like discourse structure. Typical subjects increase the range of word recurrence over school years, but the same feature in subjects with psychosis resists education.

Verbal Short‐Term Memory Underlies Typical Development of “Thought Organization” Measured as Speech Connectedness

“…This is exactly what was found in schizophrenia, since the first symptomatic manifestations (Mota et al, ). Moreover, in typical development, the more years of education, the farther from randomness is the connectedness of memory reports, an association not found in the occurrence of psychosis (Mota et al, ). This suggests that verbal memory is linked to this ability to produce a well‐connected report, a measure linked to FTD, and that probably verbal short‐term memory is associated with FTD.…”

“…In average, the total time to collect data from one child was 10 min. The verbal reports were collected using the same protocol and the same pictures used in previous studies of speech connectedness (Mota et al, , , , ). Using a laptop, we presented three affective photos from the IAPS database (Lang, Greenwald, Bradley, & Hamm, ), which has been previously validated in children: one positive (e.g., a baby in a bathtub), one negative (e.g., a plane crash scene), and one neutral (e.g., a truck on a road).…”

“…For instance, FTD symptoms such as aberrant word flow are amenable to precise mathematical estimation. Nonsemantic word graphs, in which each node represents a word, and each directed edge represents the temporal order of consecutive words, have been shown to be quite informative even in the case of the limited samples of oral discourse collected in naturalistic settings, such as clinics or schools (Mota et al, , ; Mota, Copelli, & Ribeiro, ; Mota, Furtado, Maia, Copelli, & Ribeiro, ; Mota, Sigman, Cecchi, Copelli, & Ribeiro, ; Palaniyappan et al, ).…”

“…Next we investigated the development of LSC in relation to age and education, using a larger sample ( n = 214) with a wide range of ages (2–60 yo) and educational levels (0–20 years of education), comprising individuals with and without psychotic symptoms (Mota et al, ). Among the typical individuals we found positive correlations with both age and education, but years of education explained the variation better than years of age.…”

“…While the correlation with education was independent from age, the reverse was not true. Interestingly, among the psychotic individuals there were no significant correlations with either age or education (Mota et al, ).…”