“…Clinical populations, such as those with PTSD, exhibit impaired reduction in CS+ responses during extinction and recall of learned extinction compared to healthy controls (Milad et al, 2009;Wessa & Flor, 2007). Despite the translational basis of fear conditioning and extinction research, there are some existing issues with its operationalization in the laboratory (Bach et al, 2018;Beckers, Krypotos, Boddez, Effting, & Kindt, 2013;Lonsdorf et al, 2017;Lonsdorf & Merz, 2017;Sjouwerman, Niehaus, Kuhn, & Lonsdorf, 2016). Group differences between healthy and clinical populations, such as anxiety for which the primary aetiological mechanism is believed to be fear extinction, are often undetectable in individual studies and may only emerge in meta-analysis as negligible, small or small-moderate effect sizes, which have been reported before correction for publication bias (Beckers et al, 2013;Duits et al, 2015;Lissek et al, 2005).…”