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Isabelle Charbonneau, Joël Guérette, Caroline Blais, Stéphanie Cormier, Fraser Smith, Daniel Fiset; Discrimination of facial expressions and pain through different viewing distances. Journal of Vision 2019;19(10):180c. doi: https://doi.org/10.1167/19.10.180c.
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© ARVO (1962-2015); The Authors (2016-present)
Due to its important communicative function, a growing body of research has focused on the mechanisms underlying the recognition of the facial expression of pain. A study suggested that pain recognition relies on the use of low spatial frequencies (SFs; Wang et al., 2015) although another study has highlighted the importance of mid-SFs (Guérette et al., VSS 2018). With the aim of clarifying these contradictory results, we manipulated the effect of distance, a method that better reflects the reality of clinicians who may have to recognize pain from a near or a far distance. Importantly, changes in viewing distance modulate the available SFs by progressively removing high-SFs as the stimulus moves further away. With a concern to replicate previous findings (Smith & Schyns, 2009), the six basic emotions and neutral were also included in the experiment which consisted of an 8-expression categorization task (16 participants; 2400 trials per participant). The Laplacian Pyramid toolbox (Burt & Adelson, 1983) was used to create six reduced-size images simulating increasing viewing distances (3.26, 1.63, 0.815, 0.41, 0.20, 0.10 degree of visual angle). Unbiased hit rates (Wagner, 1993) were calculated to quantify the participants’ performance at each distance. A 6 × 8 (Distance × Emotion) repeated-measures ANOVA revealed a significant interaction F(8.54,128.22)=15.97, p< .001 (η2=0.516). Separate repeated-measures ANOVAs looking at the effect of Emotion for each Distance were conducted and follow-up paired sample t-tests (corrected p=0.05/28) revealed significant differences between expressions. Most importantly, recognition of pain decreased with increasing viewing distances and was not recognized above chance level at further distances, whereas surprise and happiness were the best two recognized expressions at these distances (all p’s< .05). These results support the central role of mid-SFs for the recognition of pain.
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