P3b amplitudes differences in ultra-rapid visual categorization task of food and non-food items

Abstract

P300, especially P3b, the third positive wave of EEG signal with near 350ms associated with occipito-patieto-temporal region of the brain, is mainly responsible for categorization of different objects. So, this study investigates the nature of amplitude and reaction time difference in ‘food’ and ‘no-food’ objects categorization task. Object categorization processes were investigated by measuring event-related potentials while participants were categorizing different ‘food’ and ‘no-food’ items. The EEG study of this experiment found no P3b amplitude differences for ‘food’ and ‘no-food’ category in the ultra-rapid categorization task. On the other hand, from the behavioral study we observed no significant difference in both reaction time (RT) and error rate (ER) in the above task. The result of this study is consistent with some previous experiments. For example, regarding the reaction, the findings can be compared with VanRullen & Thrope (2001) who also found no significant longer reaction time for ‘means of transport’ item in comparison with ‘animal’. The result of this study can also be interpreted from the perspective of ‘coarse-to-fine account’ hypothesis (Prass et al. 2013) which indicated that to recognize objects belong to basic level category one needs detail information with sufficient time. Since this study includes ultra-rapid visualization task participants did not get enough time to process objects of two different categories. Hence both reaction time and error rate were not significant in this regard.