There’s some debate surrounding the concept of ego depletion — the idea that you have a finite amount of mental energy to spend before you become decision-fatigued — but even for someone with infinite willpower, making all those choices with a partner can be a fraught, highly delicate balancing act, says psychology professor Julie Peterson, who leads the Self and Close Relationships Lab at the University of New England. Shopping for a high-stakes item is stressful even when you’re on your own, “but then you add a relationship partner to that — who you care about, love, ostensibly want to please in some way — and it it just compounds it even more,” she says. “Any big shopping experience, when you’re doing it as a dyad, it becomes ripe for conflict … [You have] so many choice options, and then on the other hand you have this sort of burden of balancing your needs and desires with your partner’s needs and desires, and as a result it kind of creates this perfect storm.”

Which, in turn, can magnify any disagreements, infusing the Ektorp and the Knopparp with a symbolism they don’t really deserve. Suddenly, a chair isn’t just a chair — it’s a metaphor for all the ways you’re incompatible. If you’ve seen that 30 Rock episode, you may remember that excellent moment when a man tells his female companion, “I’m just not sure that my chair wants to be with this table.” Her reply: “Why, because deep down your chair would rather be with other chairs? … The table thinks the chair takes too many camping trips with Richard.” It may be an exaggeration, but not a huge one: “People misattribute that arousal, that ‘We can’t even agree on a chair,’ to something that’s indicative of their relationship,” Peterson says, “when likely it’s just indicative of all these other forces working on their really limited cognitive capacity at that moment.”

Once the arguing starts, you find yourself trapped: both literally, in that it’s impossible to find your way out of Ikea, and figuratively, in that the fight can bring unrelated past grievances to the surface. “Disagreement puts people in a negative mood state, and when you’re in a negative mood state, you actually remember more negative things,” says Ozlem Ayduk, a psychologist who heads up the Relationships and Social Cognition Lab at the University of California, Berkeley. It’s a process called “mood-congruent memory recall”: If you’re happy, you’re more inclined to look back on happy memories. If, on the other hand, you’re peeved because your better half has spent an hour going back and forth on the same two sofas, you’re more likely to recall other times when they made your life harder by dawdling.