This study considers the principle that governs syntactic parser's revision processes by investigating how the parser resolves temporary ambiguities which emerge during reanalysis. Previous studies which addressed this issue have argued that the parser prefers preserving as many existing structure and interpretation as possible. This study, however, argues that the hypothesis emphasizing preserving the existing structure needs to be revised and presents the Error Signal-based Revision Principle (ESRP). The ESRP requires the parser to constructs a maximal projection which has a minimal number of nodes dominating the error signal and can be attached into the existing structure in a legitimate way such that the rules of grammar are not violated. We demonstrate that the ESRP can correctly explain the parser's preference in resolving temporary ambiguities during reanalysis. Furthermore, we present empirical evidence from an experiment employing the event-related brain potentials (ERPs) technique which indicate that the ESRP is more plausible than the structure-preserving principle as an ambiguity-resolution principle. Finally, we argue that the ESRP is consistent with the assumption that the parser performs its task in the “least effort” way.