The relationship between delusional ideation/schizotypy tendencies and global-local processing : an eye movement study

Abstract

Differential global–local processing and eye movement patterns between individuals with schizophrenia and healthy individuals were documented in the literatures. Schizophrenics were found to have global processing deficit but intact or even be advantageous in local processing. Nevertheless, the findings were equivocal and most if not all studies, were conducted with the involvement of Westerners or East Asians residing in the West. The current study aimed to examine the relationships, using healthy individuals with delusional ideation / schizotypy tendencies as an analogue of schizophrenia, in the local population. A total of 77 college students were recruited and reported their delusional ideation (Peters et al Delusions Inventory; PDI–21) and schizotypy tendencies (Schizotypal Personality Questionnaire; SPQ). Face Recognition Task, Embedded Figures Test (EFT), Contour Integration Test, and Navon Task were administered to examine different facets of global–local processing. Cognitive abilties were measured by Trail Making Test, The Chinese version of Stroop Color-Word Test – Victorian version, Flanker Task, Verbal and Spatial two-back Tasks, and Tower of London Test. The Eye Movement analysis with Hidden Markov Models (EMHMM) approach was adopted to investigate eye movement patterns during the Face Recognition Task. Individual eye movement patterns were clustered to reveal two common eye movement patterns. The eye movement patterns were also quantified as H–A scale. The participants were divided into high or low level groups of PDI (i.e., total score) and SPQ (i.e., three factor scores: Cognitiveperceptual, Interpersonal, and Disorganized Features) by median split for analyses. Using independent samples t-test, significant group differences in reaction time of EFT and accuracy of Contour Integration Test were found between those with higher levels of Cognitiveperceptual score and their lower level counterparts, sugeesting the higher level group had poorer performance. Participants with higher levels of Interpersonal score were more likely to adopt a holistic eye movement pattern than those with lower levels. Correlational analyses revealed an inverse relationship between Cognitive-perceptual score and accuracy of Contour Integration Test and a positive relationship between Interpersonal score and H–A scale. Although participants scored higher and lower in Interpersonal score were found to marginally differ in reaction time of Contour Integration Test, significant positive relationship was identified by correlational analyses. Using stepwise regression analyses, reaction time of Contour Integration Test was identified as a significant predictor of all three SPQ factor constructs, whereas subscale score No Close Friends of SPQ was found to be related to H–A scale. The current study provided some preliminary evidence on the differential global–local processing and eye movement patterns in local, healthy individuals with schizotypy tendencies. Schizophrenics’ differential patterns in global–local processing might be owning to their difficulties in attending to the relevant stimuli while ignore the irrelevant stimuli and in integrating the local elements to form a perceptual whole. More studies with the involvement of local population were necessary and of clinical significance to unravel whether the differential performance and eye movement patterns could serve as markers or constitute the phenotype of schizophrenia for early detection and prevention.