Categorical perception of morphed objects using a free-naming experiment Mijke O. Hartendorp and Stefan Van der Stigchel Helmholtz Institute, Experimental Psychology, Utrecht University, Utrecht, The Netherlands Hollie G. Burnett and Tjeerd Jellema Department of Psychology, University of Hull, Hull, UK Paul H. C. Eilers Department of Methodology and Statistics, Utrecht University, Utrecht, The Netherlands Albert Postma Helmholtz Institute, Experimental Psychology, Utrecht University, Utrecht, The Netherlands Morphed figures entail a dominant and nondominant interpretation. Testing perception of morphed objects using forced-choice methods demonstrates that morphed figures are perceived as their dominant interpretation (‘‘categorical perception’’, or CP). Using a more natural free-naming response could reveal whether CP is an effect independent of method. In Experiment 1, therefore, series of morphed figures were tested for CP using free naming. Half of the morph series were identified as CP patterns. In Experiment 2, we used forced choice to investigate CP, resulting in an increase of number of CP series compared to free naming. The overlap between CP series of Experiments 1 and 2 was small, however. Experiment 3 revealed that higher perceptual similarity between the extremes of the series was strongly related to CP for the free-naming method, in contrast to the forced-choice method. We conclude that the observation of CP depends on the intactness of the intrinsic object structure caused by the morphing procedure. Please address all correspondence to Mijke Hartendorp, Experimental Psychology, Helmholtz Institute, Universiteit Utrecht, Heidelberglaan 2, 3584 CS Utrecht, The Netherlands. E-mail: M.O.Hartendorp@uu.nl This work was supported by the Unconscious Boundaries of Mind project of the European Science Foundation. We thank Jeanette Mostert and Sander Bosch for their help to set up the experiment and to run participants, and Katinkavan der Kooij for her help in the analyses. VISUAL COGNITION, 2010, 18 (9), 13201347 # 2010 Psychology Press, an imprint of the Taylor & Francis Group, an Informabusiness http://www.psypress.com/viscog DOI: 10.1080/13506285.2010.482774