The processing of perceptual similarity with different features or spatial relations as revealed by P2/P300 amplitude

• Published in: International journal of psychophysiology Vol. 95; no. 3; pp. 379 - 387
• Main Authors: Chen, Qingfei, Liang, Xiuling, Li, Peng, Ye, Chun, Li, Fuhong, Lei, Yi, Li, Hong
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.03.2015
• Subjects: Brain Mapping; Difference judgment; Electroencephalography; ERPs; Event-Related Potentials, P300 - physiology; Female; Humans; Judgment - physiology; Male; P300; Pattern Recognition, Visual - physiology; Photic Stimulation; Reaction Time - physiology; Similarity judgment; Space Perception - physiology; Time Factors; Young Adult; Similarity judgment; ERPs; P2; P300; Difference judgment
• ISSN: 0167-8760; 1872-7697; 1872-7697
• DOI: 10.1016/j.ijpsycho.2015.01.009

Visual features such as “color” and spatial relations such as “above” or “beside” have complex effects on similarity and difference judgments. We examined the relative impact of features and spatial relations on similarity and difference judgments via ERPs in an S1–S2 paradigm. Subjects were required to compare a remembered geometric shape (S1) with a second one (S2), and made a “high” or “low” judgment of either similarity or difference in separate blocks of trials. We found three main differences that suggest that the processing of features and spatial relations engages distinct neural processes. The first difference is a P2 effect in fronto-central regions which is sensitive to the presence of a feature difference. The second difference is a P300 in centro-parietal regions that is larger for difference judgments than for similarity judgments. Finally, the P300 effect elicited by feature differences was larger relative to spatial relation differences. These results supported the view that similarity judgments involve structural alignment rather than simple feature and relation matches, and furthermore, indicate the similarity judgment could be divided into three phases: feature or relation comparison (P2), structural alignment (P3 at 300–400ms), and categorization (P3 at 450–550ms). •The processing of features is dissociated from the processing of spatial relations.•The P2 amplitude was modulated by whether a feature difference is present.•Larger P3 was elicited by difference judgment than by similarity judgment.•Similarity and difference depend on structural alignment with different outputs.•Similarity involved feature comparison, structural alignment, and categorization.