kantahayashi
4 hours ago
I tested Jev with a fair die 400 times without telling it the die result. The true probability of face 1 is 1/6, but Jev always chose face 1 and the probability it returned was about 83%. I also tested with a fair coin 200 times and got 0.92 probability.
I did several tests and I think Jev is good at problems with a correct answer but weak at problems about actual probabilities whose answers can't be known at all.
Write-up: "Jev Does Not Play Dice" https://kantahayashiai.github.io/posts/jev-does-not-play-dic...
drtz
3 hours ago
In the early Gemini 2 days (don't remember which version exactly) I had Gemini running as a voice assistant in my kitchen, and asked it to flip a coin and tell me if it was heads or tails. It responded with "heads". I was curious if it was actually doing something to simulate randomness, so I asked a few more times and saw a pattern: "tails", "heads", "tails", "heads"...
It continued alternating between the two until I got bored (around a dozen turns).
Unless your specific test is baked into its training, real probabilities require math and rough approximation at a minimum needs reasoning to sanity-check. Jev does neither. This isn't a new problem or anything unique to Jev.
tomrod
3 hours ago
The value of grandparent comment is that it identifies an edge case to keep in mind and make well-defined -- keeps us from blindly trusting.
edot
3 hours ago
Hah! I did the exact same tests as you! I found that if you give it the choice to say "not sure", it picks that 100% of the time. But if you pin it in a corner, then yes it does these weird things. Also yes, the continuous options were much more accurate than the choices. Not sure why that is.
throwaway_7274
3 hours ago
If you instead offer probabilities as answers, it picks the right one with high credence.
alexmolas
4 hours ago
But "problems about actual probabilities whose answers can't be known at all" are exactly the problems where calibration is important. Since calibration is one of the big claims about Jev I'd expect it to perform well in these problems.
kantahayashi
3 hours ago
I agree. I think it's odd behavior too. Jev should be good at actual probability problems given the phrase "calibrated probabilities" TypeSafe uses for Jev. Maybe the reason is the data used in their training method (RLCD). If all the data consists of problems with a correct answer, I think this kind of odd behavior could happen.
tomrod
3 hours ago
Echoes a bit of a philosophical distinction with a long history: "Knightian Uncertainty" versus "Probability".
seizethecheese
3 hours ago
Maybe I’m confused here, but it’s perfectly reasonable to just guess the same dice roll every time right?
kantahayashi
3 hours ago
Yes. There's no problem with choosing the same face every time. The problem is the probability it attached to the choice. Jev gave face 1 an 83% probability while the true probability is 1/6.
seizethecheese
3 hours ago
Okay, I see, you're expecting Jev to properly give 1/6 probability for each option. This is different from my intuition of how LLMs work, where their probabilities don't really work like this (I would expect LLM to also do something like 0.83 for 1).
kantahayashi
2 hours ago
That's right. It's normal behavior of LLMs. But what matters is TypeSafe argues it's different exactly on this point. The selling point of Jev is "calibrated probabilities", so I checked it on probability problems.
maayank
2 hours ago
Jev and LLMs give other promises. Jev's RLCD training aims to make its probabilities calibrated such that given many cases where it assigns label Y about X% probability, Y should be the correct label about X% of the time.
sshine
3 hours ago
Do you provide Jev that the probability is 1/6 and yet it gives back a probability that is way off?
kantahayashi
3 hours ago
Yes. For example, one of the prompts said "The die is unbiased: each of the six faces has probability exactly 1/6."
dgritsko
3 hours ago
Reminds me of this... https://xkcd.com/221/
alexmolas
3 hours ago
I don't know if it's reasonable. What it isn't is calibrated.
lesam
3 hours ago
So you want the probability that the answer is correct, but Jev is providing the probability that its answer is optimal?
kantahayashi
2 hours ago
Yes, and TypeSafe itself says Jev returns "calibrated probabilities", which is the former.
From TypeSafe docs:
"Higher probability should correspond to a greater chance that the answer is correct."
"Outcomes assigned a probability of 0.2 should occur about 20% of the time."
https://docs.typesafe.ai/introduction/machine-learning-prime...
scotty79
3 hours ago
Did you expect it to be good at it?
Humans also don't give a perfect 1/n probability when asked for a random number.
formerly_proven
3 hours ago
Humans give way more random answers than LLMs to questions like "give me a random number between 1-100" (when not giving the LLM any tool calls).
tomrod
an hour ago
Typically not! The distribution is not uniform.
esperent
2 hours ago
> The true probability of face 1 is 1/6, but Jev always chose face 1 and the probability it returned was about 83%
I think this is a misunderstanding of what that 83% probability means. You think you're asking Jev to assign a probability to a dice roll, and if so then obviously it should pick each answer 1/6 of the time.
However, what Jev is doing is assigning a probability to the answer it should choose. And it's choosing 1 with 83% probability, as the correct answer to give, when there's no additional knowledge available.
1 is a perfectly valid answer here. In the absence of other data there's no more (nor less) valid answer than that. and I assume that just like LLMs, the token prediction must assign higher probability to one outcome.
If you keep feeding the previous answers back in (if you can do that with Jev) I assume it would start giving other numbers because it's no longer operating from zero info. Maybe that would even reach ~1/6 after enough rounds, although maybe not.
kantahayashi
an hour ago
TypeSafe defines the probabilities Jev returns as "calibrated probabilities". "Probability" here means the probability of the answer being correct. If the probability is 10%, the choice should be correct about one time in ten. So, when Jev returns 83% probability it should be correct about 83 times out of 100, but the choices were only correct about 19 times out of 100, and the true probability is 1/6.
"Higher probability should correspond to a greater chance that the answer is correct."
https://docs.typesafe.ai/introduction/machine-learning-prime...
bee_rider
2 hours ago
As someone who hasn’t used Jev, this seems reasonable in the sense that “probability that I’ve given the best answer” seems like a useful thing to provide.
Anyway, if it is “probability that I gave the best answer” why 83%? I mean, the question is a sort of a textbook-style probability question in the sense that everything is well defined. Shouldn’t it be basically 100%?