Under federal law, marijuana and heroin are in the same legal regulatory category: Schedule 1. It's a surprising fact — one that's commonly cited by marijuana legalization advocates as a way to show how bizarre US drug policies can appear.

But a new poll from Vox and Morning Consult shows that most Americans don't know that marijuana is in the same legal category as heroin — or, in fact, where other illicit drugs lie in the federal scheduling system.

For the poll, Vox and Morning Consult first defined the federal schedules for nearly 2,000 registered voters in the US. Schedule 1 means a drug has no medical value and a high potential for abuse. Schedule 2 to 5 means a drug has some medical value and high to low potential for abuse, with a lower potential for abuse as the schedule descends. Generally, Schedules 1 and 2 are most restrictive, while Schedule 5 is least restrictive.

Then Vox and Morning Consult asked voters how they think marijuana, magic mushrooms (psilocybin), acid (LSD), ecstasy or molly (MDMA), ibogaine, cocaine, heroin, and methamphetamine are scheduled, and how those drugs should be scheduled.

The results, visualized by Javier Zarracina at Vox:

Most Americans don't appear to know how any of the listed drugs are scheduled. A majority of respondents failed to give the right answer for every single drug.

It was particularly bad for marijuana. People were fairly evenly divided — between all five schedules and no schedule at all — on what pot's schedule is and should be. There was, however, a significant shift to a laxer classification when respondents were asked what the schedule should be.

The confusion for marijuana in particular may reflect its confusing legal status right now in the US. Although it's strictly prohibited and Schedule 1 at the federal level, 23 states allow it for medical purposes, and Colorado, Washington state, Oregon, Alaska, and Washington, DC, allow it for recreational use.

It's also possible that Americans think the federal government already shares their belief that marijuana is relatively safe and therefore shouldn't be a Schedule 1 substance. After all, about 69 percent of Americans say marijuana is less harmful to a person's health than the fully legal — and unscheduled — alcohol, according to a 2014 survey from the Pew Research Center.

For the non-marijuana drugs, respondents seemed very likely to choose Schedule 1 as their response. Because of the drugs chosen for the survey, this was generally a good way to get the right answer — for marijuana, psilocybin, LSD, MDMA, ibogaine, and heroin. But it was the wrong answer for two drugs: cocaine and methamphetamine, which are legally allowed at the federal level for some medical uses.

Overall, Americans seem deeply confused about the scheduling system. So maybe they should all check out — and widely share on social media to help educate their friends — Vox's explainer.

Morning Consult polled 1,994 registered voters between March 10 and March 13, 2016. The interviews were conducted using large, established online survey vendors and were weighted to approximate a target sample of registered voters based on age, race/ethnicity, gender, educational attainment, region, annual household income, home ownership status, and marital status. Results from the full survey have a margin of error of +/- 2 percentage points. Topline results are available here, and cross-tabulation results are available here.