Categorical perception of morphed objects using a free-naming experiment

Abstract

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.

Keywords:

• Object categorization
• Categorical perception
• Free naming

Acknowledgements

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 Katinka van der Kooij for her help in the analyses.

Notes

¹We acknowledge that labelling a series as CP or non-CP is slightly arbitrary and is an example of dichotomous categorization itself. However, we argue that our distinction is defendable; CP is a well-described phenomenon in the literature from which we have inferred conservative criteria that a series should fulfil before being labelled as a CP series.