They explain the possible A/C confound like this: “We don’t know what the kid is doing 2 hours before the test implementer arrives at the house, it’s quite pos

They explain the possible A/C confound like this: “We don’t know what the kid is doing 2 hours before the test implementer arrives at the house, it’s quite possible the kids are outside,” he says. “It’s quite possible these kids are exposed to some heat even if they can then come in and cool off.” I actually had a different and precisely contradictory explanation: the test-takers on hot days were more likely to be in heavily air-conditioned environments and thus the air in the test-taking environment is too cold (and dry, and probably mouldy). It's certainly an interesting effect but they need to do a lot more work to establish the cause.