{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,29]],"date-time":"2026-10-29T12:33:00Z","timestamp":1793277180576,"version":"4.5.0"},"reference-count":37,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,7,29]],"date-time":"2026-07-29T00:00:00Z","timestamp":1785283200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Psychol."],"abstract":"<jats:sec>\n                    <jats:title>Introduction<\/jats:title>\n                    <jats:p>\n                      Emotion recognition through facial expressions is crucial for interpreting social cues. However, it is often influenced by biases, i.e., systematic recognition advantages for particular emotions. Nevertheless, these biases are inconsistently reported across studies, likely due to methodological variations which underline the necessity for a standardized approach. Traditional face morphing methods can create unnatural-looking stimuli, and may confound the interpretation of emotions. To address this issue, we here introduce\n                      <jats:italic>STEMorph<\/jats:italic>\n                      , a validated stimulus set based on the NimStim set.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>We employed neutral-anchored morphing and neural-network-generated masks to reduce morphing artifacts and preserve the coherence of the depicted expressions. We validated our stimulus set by having participants rate each face on a 9-point scale ranging from angry to happy, assessing the perceived emotional intensity. Reliability was assessed through a two-week follow-up rating session with a subgroup of the same participants.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      <jats:italic>STEMorph\u2019s<\/jats:italic>\n                      validity was confirmed through linear mixed-effects modeling, showing a strong association between subjective ratings and intended morph level (\n                      <jats:italic>\u03b2<\/jats:italic>\n                      = 0.735,\n                      <jats:italic>p<\/jats:italic>\n                      &amp;lt; 0.001) while accounting for other effects and explaining a large proportion of variance (marginal\n                      <jats:italic>R<\/jats:italic>\n                      \u00b2 = 0.725). Moreover, aligning with previous research highlighting gender as a key factor in emotion recognition, STEMorph also showed variation across participant-gender dimension (\n                      <jats:italic>\u03b2<\/jats:italic>\n                      = 0.325,\n                      <jats:italic>p<\/jats:italic>\n                      &amp;lt; 0.001).\n                      <jats:italic>STEMorph\u2019s<\/jats:italic>\n                      reliability was confirmed through high agreement between initial and follow-up ratings (ICC = 0.858).\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Discussion<\/jats:title>\n                    <jats:p>\n                      By introducing a controlled and empirically evaluated stimulus set of morphed emotional faces,\n                      <jats:italic>STEMorph<\/jats:italic>\n                      provides a useful resource for future investigations of facial emotion recognition.\n                    <\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fpsyg.2026.1751625","type":"journal-article","created":{"date-parts":[[2026,7,29]],"date-time":"2026-07-29T04:45:12Z","timestamp":1785300312000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["STEMorph: a set of morphed emotional face stimuli from angry to happy derived from NimStim"],"prefix":"10.3389","volume":"17","author":[{"given":"Mohammad Ebrahim","family":"Katebi","sequence":"first","affiliation":[{"name":"School of Cognitive Sciences, Institute for Research in Fundamental Sciences","place":["Tehran, Iran"]},{"name":"School of Medicine, Tehran University of Medical Sciences","place":["Tehran, Iran"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mohammad Hossein","family":"Ghafari","sequence":"additional","affiliation":[{"name":"School of Medicine, Shahid Beheshti University of Medical Sciences","place":["Tehran, Iran"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Tara","family":"Ghafari","sequence":"additional","affiliation":[{"name":"Department of Experimental Psychology, University of Oxford","place":["Oxford, United Kingdom"]},{"name":"Oxford Centre for Human Brain Activity (OHBA), Oxford Centre for Integrative Neuroimaging (OxCIN), Department of Psychiatry, University of Oxford","place":["Oxford, United Kingdom"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2026,7,29]]},"reference":[{"key":"ref1","year":"2016"},{"key":"ref2","doi-asserted-by":"publisher","first-page":"171","DOI":"10.13140\/2.1.4881.4723","article-title":"A comparison of backward masking of faces in expression and gender identification","volume":"35","author":"Aguado","year":"2014","journal-title":"Psicol\u00f3gica"},{"key":"ref3","doi-asserted-by":"publisher","first-page":"433","DOI":"10.1163\/156856897X00357","article-title":"The psychophysics toolbox","volume":"10","author":"Brainard","year":"1997","journal-title":"Spat. 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