Abstract
The question whether facial expression processing may be impaired in Parkinson’s disease (PD) patients so far has yielded equivocal results – existing studies, however, have focused on testing expression processing in recognition tasks with static images of six standard, emotional facial expressions. Given that non-verbal communication contains both emotional and non-emotional, conversational expressions and that input to the brain is usually dynamic, here we address the question of potential facial expression processing differences in a novel format: we test a range of conversational and emotional, dynamic facial expressions in three groups – PD patients (n = 20), age- and education-matched older healthy controls (n = 20), and younger adult healthy controls (n = 20). This setup allows us to address both effects of PD and age-related differences. We employed a rating task for all groups in which 12 rating dimensions were used to assess evaluative processing of 27 expression videos from six different actors. We found that ratings overall were consistent across groups with several rating dimensions (such as arousal or outgoingness) having a strong correlation with the expressions’ motion energy content as measured by optic flow analysis. Most importantly, we found that the PD group did not differ in any rating dimension from the older healthy control group (HCG), indicating highly similar evaluation processing. Both older groups, however, did show significant differences for several rating scales in comparison with the younger adults HCG. Looking more closely, older participants rated negative expressions compared to the younger participants as more positive, but also as less natural, persuasive, empathic, and sincere. We interpret these findings in the context of the positivity effect and in-group processing advantages. Overall, our findings do not support strong processing deficits due to PD, but rather point to age-related differences in facial expression processing.
Highlights
Human communication is rich with both verbal and non-verbal signals, enabling us to act and interact in highly complex social situations
The first analysis was concerned with assessing the absolute variability of the rating values across the three tested groups, that is, how the raw ratings gathered from participants varied for each of the ratings dimensions and in each of the groups
How facial expression processing may be affected by the presence of Parkinson’s disease (PD) or age-related factors has so far been addressed mainly in the context of recognition experiments on the so-called universal expressions
Summary
Human communication is rich with both verbal and non-verbal signals, enabling us to act and interact in highly complex social situations. Several emotional expressions were tested across different literate and pre-literature cultures and it was found that six facial expressions were recognized well in all cultures – these are anger, disgust, fear, happy, sad, and surprised and have since become known as the “basic” or “universal” facial expressions (Ekman and Friesen, 1971) as well as coded in terms of specific muscle movements the Facial Action Coding System (FACS) (Ekman and Friesen, 1978) These six expressions are referred to as “universal,” various studies have reported differences in perception and production of facial expressions depending on gender (Ebner et al, 2010), cultural and ethnic background (Matsumoto, 1993; Jack et al, 2009, 2012a,b; Jack, 2013), as well as age (Ebner et al, 2010). There are significant agerelated differences that modulate the perception and production of facial expressions
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