Poster D109, Monday, March 26, 8:00-10:00 am, Exhibit Hall C
When “2 x 4” is meaningful: the N400 and P300 reveal operand format effects in multiplication
Vanessa Cerda1, Danielle S. Dickson1, Rosemary N. Beavers2, Andres G. Ruiz3, Nicole Y. Y. Wicha1,4; 1University of Texas at San Antonio, 2University of Texas Medical Branch, 3Texas Tech University Health Sciences Center, 4University of Texas at San Antonio Neurosciences Institute
When people read the solution to 3x4 =12 versus 3x4 =15 the brain elicits a robust event-related potential (ERP) effect. Initially, this effect was interpreted as a negative voltage modulation to the incorrect solution – an N400, implying that accessing arithmetic facts relies on a semantic memory network. This was consistent with models that argued for verbal memory representation of arithmetic facts. Subsequent work suggested instead that it was driven by a positive-going response to detecting the correct solution – a target P300. In the current study, operand format was manipulated to differentially promote access to arithmetic facts in verbal memory. Adults verified the correctness of simple multiplication problems. Two operands were presented as spoken number words or sequential Arabic numerals. The solution was always an Arabic numeral; ERPs were measured from solution onset. In Experiment 1, solutions preceded by spoken operands showed larger N400 amplitude for incorrect than correct problems, whereas solutions preceded by Arabic numerals showed a large P300 for correct problems. In Experiment 2, using only spoken operands, the delay between the second operand and the solution was manipulated (150ms, 1000ms) to determine if additional processing time would result in a P300, as with digit operands in Experiment 1. With a longer delay, an earlier N400 and no P300 was observed. In brief, highly familiar digit operands promote target detection, whereas spoken numbers promote semantic level processing even when solution format was held constant. This implies that format affects access to arithmetic facts in semantic memory.
Topic Area: THINKING: Problem solving