Are negative numbers processed differently than positive numbers in arithmetic problems?In two experiments, adults (N = 66) solved standard addition and subtraction problems such as 3 + 4 and 7 -4 and recasted versions that included explicit negative signs, that is, 3 -(-4), 7 + (-4), and (-4) + 7. Solution times on the recasted problems were slower than on standard problems, but the effect was much larger for addition than subtraction. The negative sign may prime subtraction in both kinds of recasted problems. Problem size effects were the same or smaller in recasted as compared to standard problems, suggesting that the recasted formats did not interfere with mental calculation. These results suggest that the underlying conceptual structure of the problem (i.e., addition vs. subtraction) is more important for solution processes than the presence of negative numbers.Negative Numbers -3
Negative Numbers in Simple ArithmeticAre negative numbers processed differently than positive numbers in arithmetic problems? Negative numbers are thought to be conceptually difficult for both children and adults (De Cruz, 2006). Although no one has addressed the question of whether negative numbers interfere with solving arithmetic problems, there is evidence suggesting that negative terms (e.g., 6 -x = 4) might be more difficult for students to process than positive terms in algebraic equations (Peterson & Aller, 1971;Vlassis, 2004). We hypothesized that arithmetic problems with negative numbers may be processed differently because they usually require subtraction, rather than because of the negative number, per se. Subtraction is slower and more error-prone than addition (Campbell & Xue, 2001;LeFevre, DeStefano, Penner-Wilger, & Daley, 2006;Seyler, Kirk, & Ashcraft, 2003). On this view, the conceptual structure of the problem (i.e., the mental operation that is required) is the critical determinant of processing difficulty rather than the presence of a negative number.In the present research, adults solved addition and subtraction problems in standard formats, that is 3 + 4 and 7 -4, and as addition or subtraction of negative numbers in recasted formats, that is, 3 -(-4), 7 + (-4) and (-4) + 7. In the recasted formats, the conceptual structure of the problem did not change but the format was manipulated to explicitly isolate a negative number. Shaki and Petrusic (2005) outlined two hypotheses about how people process negative numbers. According to the magnitude-polarity hypothesis, the magnitude of the number and the polarity (i.e., positive vs. negative) are processed independently, as distinct features of the stimulus. In contrast, according to the number-line hypothesis, people represent negative and positive numbers along a number line, with negative numbers extending to infinity on the left and positive numbers extending to infinity on the right. Accordingly, the negative or positive status of the number is integral to mental processing. Ganor-Stern and Tzelgov (2008) The most common use of negative signs in arit...