Interaction of numbers and spatial attention in Iranian people

Abstract

Abstract Introduction Previous studies on mental representation of numbers have shown an interaction between numbers and space. This representation is called mental number line with small numbers in left and big numbers in right. It is affected by writing direction. The aim of this study was to investigate number-space interaction and its nature considering the characteristics of Persian writing system. Method In the first experiment 30 undergraduate students volunteered to complete two symbolic and non-symbolic Posner’s attentional tasks. In second experiment 37 new students completed the symbolic task and their ERPs were recorded meanwhile. Results Data were analyzed by repeated-ANOVAs. There was no interaction between magnitude and side (F=0.437, p=0.51). The main effect of magnitude was significant (F=5.21, p=0.03). Dot detection after small numbers were responded faster (468±13 ms) than bigger numbers (475±14). Response times for symbolic quantities (464±13) were faster than non-symbolic quantities (479±14) (F=5.12, p=0.03). Similarly, in the second experiment, main effect of magnitude was significant (F=9.612, p=0.005). No main effect or interaction for latency of P300 was significant. Conclusion Behavioral results showed the size effect. However no interaction of magnitude by side (SNARC effect) was seen. In other words magnitude did not shift the mental attention to left or right. Behavioral findings were not verified by ERP results. In summary, affected by Persian writing system, there was no interaction between numbers and space contrary to other languages except Hebrew. In addition, this study indicated that the source of this variation is not at perceptual level and it should be investigated at other levels. Keywords Number, mental representation, attention