the claim that parties emerge from existing cleavages, or arguing that the claim is not empirically testable. Others note that while social cleavages might cause political parties to exist, this obscures the opposite effect: that political parties also cause changes in the underlying social cleavages. A further objection is that, if the explanation for where parties come from is that they emerge from existing social cleavages, then the theory is an incomplete story of where political parties come from unless it also explains the origins of these social cleavages. Individual and group incentives An alternative explanation for why parties are ubiquitous across the world is that the formation of parties provides compatible incentives for candidates and legislators. For example, the existence of political parties might coordinate candidates across geographic districts, so that a candidate in one electoral district has an incentive to assist a similar candidate in a different district. Thus, political parties can be mechanisms for preventing candidates with similar goals from acting to each other's detriment when campaigning or governing. This might help explain the ubiquity of parties: if a group of candidates form a party and are harming each other less, they may perform better over the long run than unaffiliated politicians, so politicians with party affiliations will out-compete politicians without parties. Parties can also align their member's incentives when those members are in a legislature. The existence of a party apparatus can help coalitions of electors to agree on ideal policy choices, whereas a legislature of unaffiliated members might never be able to agree on a single best policy choice without some institution constraining their options. Parties as heuristics Another prominent explanation for why political parties exist is psychological: parties may be necessary for many individuals to participate in politics because they provide a massively simplifying heuristic, which allows people to make informed choices with much less mental effort than if voters had to consciously evaluate the merits of every candidate individually. Without political parties, electors would have to individually evaluate every candidate in every election. But political parties enable electors to make judgments about just a few groups, and then apply their judgment of the party to all the candidates affiliated with that group. Because it is much easier to become informed about a few parties' platforms than about many candidates' personal positions, parties reduce the cognitive burden for people to cast informed votes. However,