Since one of the main goal of the human brain is to take and evaluate stimuli that comes from sensory organs, it is possible to measure their functionality. In this study we classified the electroencephalography signals which were recorded during four different kinds of spice odors including peppermint, clove, thyme and rosemary were smelling. Additionally we investigated to find out which odor pair was the most discriminative by classifying all the combinations of odor pairs. The achieved classification accuracy rate of 75.96% showed that peppermint-clove odor pair was the most discriminative. Based on the obtained results it is believed that this research has increased the variability of the scent-based experiment and greatly contributes to such studies for evaluating the function of the olfactory organ.