I tend to believe Pescado because he usually gets his ideas by examining the source code. That's usually better than any number of tests, although it won't necessary tell you whether a bug is causing the randomization to fail.

simsample, it seems like you've done half of the necessary tests. The question is: how different are the sims' appearances when the randomizer is used?

Did you age the children up so that you could compare their adult appearances? Also, did you check their genetics in SimPE? It seems that starting with parents with 4 different dominant genes is the best way to run the test. If you do that for skin color, hair color, eye color, etc., then your tests would be more likely to produce variations.

That's good to know about the batbox randomizer. It's obviously a better choice than rolling the pacifier.

I've never had this problem. My sim siblings always look different and often have different zodiac signs. I have this result whether I randomize or not.

I know- I would tend to believe him too (but don't tell him I said that!). But the thing is, every test I was doing was saying the opposite. HystericalParoxysm did her own tests too because she wrote the wiki article on this; the reason I did these tests in the first place was because I sided with Pescado and disbelieved HP's observations.


Sufficiently different so that you could tell there was a difference; in just the same way as you'd see it when rolling the pacifier in CAS.


Yes, this was comparing the sims aged up to adult each time. We used the Simdna cheat to give us the genetics of the sim to compare. I've attached two examples, I'm not sure I have the images of all of the tests we did any more, but they were all the same without exception for the unrandomized sims (barring gender).



As you can see, we did it slightly differently- the father had S4 skin, blonde/blonde hair and green eyes, the mother had S1 skin, red/red hair and light blue eyes. So all recessives there. Should give the same result though, I think. Oh, and we gave them very different appearances- so the father had huge ears, the mother small; the father a long pointy nose, the mother a stubby nose and so on. The idea behind this was that any differences would be more apparent.

Edited to add: Thinking about it, I think we used sims with all dominant genes on my daughter's machine- I can't find her pictures though, I'll have to ask her if she remembers. I'm sure we used different sims on her tests to rule out any idiosyncracies.

Great. That's a much better test than just checking 3 non-randomized and 1 randomized sim.

I'm guessing that the source code shows the genetics being randomized, but a bug is causing the game to avoid the randomization logic. That would explain both Pes's insistence and the test results.

So, if there's a bug, I wonder whether there's some way to fix the bug? Or perhaps some way to get the batbox randomization to occur automatically when you start the game?

Play style is a factor in whether or not you ever see this glitch.

From the Wiki:
Firstborn syndrome may not be noticeable in your game if you tend to have more than one child per load of the game, if you often make new sims in Create a Sim first (thereby randomizing genetics when you hit "random sim"), if you use very basic facial sculpts for your sims (as most people do!) or if the parents of your sims are very similar in appearance. However, it is occurring, and if you want to have unique children, you should Roll the Pacifier!
http://www.modthesims.info/wiki.php...stborn_Syndrome

I tend to backup before babies, so I'm a prime victim.

My funniest and most annoying experience with it was in twins. A couple had boy/girl twins, then a second set of boy/girl twins with the same personalities (as the older two - not each other), except that the younger boy's personality was the same as the older girl's, and the younger girl's the same as the older boy's.

I think there was a similar mirroring of hair color, if I recall, as in the older boy/younger girl being blond and the older girl/younger boy being redheaded. They all reminded me of the four corners of a square, somehow, with a big X in the middle, connecting to each other in multiple same/opposite ways of gender, personality, and hair color.

At the time, I'd never heard of Firstborn Syndrome, so I was a bit baffled.

I hope you named them Nan, Bert, Freddy, and Flossie!

I'm usually very good about hitting the randomizer these days, but even I get caught out every now and then... I forgot to roll when one parent got pregnant (again!), and her son fell victim to Firstborn Syndrome. However, there was a slight twist; it wasn't the FIRST-born he mirrored, but the second in the family!

I'm fully aware that oldest child Daisy and her younger sister Dawn are nothing alike (I rolled before Dawn and her twin Declan were born), yet little Drew mirrors Dawn, not Daisy. By contrast, baby sister Dakota (who was born within the same game load as Drew) looks like Daisy colouring-wise - I've not checked her personality yet!

I'm sad to say I had to look that up, Peni. The phrase "Bobbsey Twins" is one I was well aware of growing up, but I never read the books. If I had, and I'd known that second set of twins was forthcoming, I may very well have used those names! :D

Same - in five years of playing, I think I've gotten my first instance of the Firstborn Effect. The couple I'm playing just had a son who has the exact same eye color, hair color, and personality points as his college-age sister. *rolls the batbox*

Once I forgot to roll the pacifier and a family was about to have their second child. I didn't save throughout the game either so the firstborn effect kicked in.

Well, they had a party with barbecue later that day <.<

After some research, I'm convinced that there is a randomization bug which causes the first-born effect for appearance, and that the bug is inside of the EXE, which means that it cannot be modded directly.

I still think that it might be possible to create a mod which just runs the batbox randomization routine when the game is started.

So are there then two sims randomizers possibly getting stuck - one for personality and one for appearance? That would seem to explain the confusion over whether or not appearance is part of the syndrome. As in, the personality randomizer always gets stuck, but the appearance randomizer only sometimes?

The game has a number of different randomizers for different things, including personality, genetics, sex, etc. There's an bug in the personality randomizer, which Pes documented. After doing some research, I'm convinced that there is also a bug in the genetics randomizer. However, the sex randomizer seems to work correctly.

The problem is that computers are not very good at being random. Instead, they are really great at doing exactly the same thing every time.

Randomizers work as follows: You provide an initial "seed" value. After that, each call to the randomizer runs an algorithm (mathematical formula) on the existing value to produce a new value. If the seed value is the same each time you run the program, then the set of "random" numbers generated will be the same, every single time.

Because of this, you want to use a random number as the seed. But remember, computers are really bad at being random, so where do you get this "random" seed? Often programmers will seed the randomizer with the time, which is likely to be random.

(Note that the time is not always a reasonable "random" seed. For example, I've heard of problems because a gambling program was started automatically at the exact same time every day. Instead of random numbers, the exact same numbers were being generated every time. Someone noticed the pattern and used that bug to win a lot of money.)

Unfortunately, it looks like the genetics seed is always the same value, which means that the "random" numbers will not be random at all. Since we don't have access to the seed, which is inside the EXE, the only other option for getting a random number is to run the randomizer a random number of times. That's why you roll the pacifier a random number of times when you start the game; you are basically running each of the randomizers when you roll the pacifier.

The Batbox does basically the same thing, because it runs the Make New Character primitive, which in turn runs each of the randomizers.

The genetics randomization bug always occurs, just as the personality randomization bug always occurs. The fact that personality and genetics use different randomizers is basically irrelevant. In both cases, the randomizers are always starting with the same value (seed) when the game starts, which means that the results are predictable.

Hope that wasn't too techie. However, you can now quote me as having done the research necessary to prove that a sim's appearance is also prone to the "first-born syndrome". The solution is the same: use the pacifier or the batbox to randomize the randomizer.

Nope, not too techie, but I do have a question. If the genetics randomization bug always occurs, just as the personality randomization bug always occurs, why is it that not all instances of the glitch include identical appearance as well as identical personality?

I thought the long-standing confusion over the whether or not appearance is an aspect of the glitch was due to some players seeing identical sims, and others not. Perhaps the apparently non-identical ones are always boy/girl, and thus harder to spot as being "identical"?

As simsample learned through extensive testing, all children born to the same parents will be identical, as long as you restart the game before each birth and don't do anything to randomize. That convinced me to do more research to see whether I could understand the reason why this was happening.

Lots of people go into CAS and create families, or have multiple births per play session, or roll the pacifier, or randomize using the batbox. All of these things will make the genetics more random. Some number of people, like me, just don't happen to notice that all of the children born to one set of parents basically look the same. Other people tend to mix their couples up more, which produces different genetics. And, as you say, sex can mask identical genetics because those genetics are expressed differently for men and women.

Its also possible that creating a new townie will run the randomizer. If a new townie or twelve are created between starting the game and giving birth, then it's possible that you'll get different genetics. Note that I can't confirm this without more research. There may be other things which run the randomizer as well.

One more thing; I only looked at one EXE. While it's hard to believe that EA actually fixed and then re-broke the randomizer seed, I suppose that it's possible. We've seen them "lose" fixes before.

Okay, that all makes sense. Thanks.


That we have.

I can confirm this from my observations- when I first began the tests I started with the two parent sims moved into a lot but forgot that the paper-boy was due. If I spawned the child after the paper-boy arrived then I got a different looking sim, so I had to save the game after the paper delivery and start again.

Great research and information, Mootilda- thank you!

I did a bit of research into this issue and it appears that there is no way to make a global mod which will roll the pacifier a random number of times when the game is started. That's because the Make New Character primitive actually creates new sims. The only way to avoid filling up your neighborhood is to enter a lot, make a number of new sims, and then exit the lot without saving. This basically means that it can't be a global mod.

I think that there is a bug in the twin generator or what ever it's called. I got around 20 sets of twins in a row until I thought to start using the bat box's randomizer before getting my sims pregnant. Then it settled down to a much more reasonable rate of twins. Even so, if I forget to roll it per-pregnancy, then I will get twins again, every single time. Highly annoying seeing as how I only occasionally like twins.

I also have a problem with my multi-pt pack always giving me the same pt parent. Bat-box can't fix that though, I have to just force someone alien pregnant through the simblender a few times terminating the pregnancy each time before letting them at the telescope or the dance sphere.

Sounds like you may have CC which is causing you problems. Does this happen if you remove all of your CC?

It was happening before I got CC. I think the only reason Dina didn't have twins is because I got her pregnant right after Nina.

Although, getting the no a+ cheer mod did get rid of it for a while. That was the only piece of CC I got before I got any expansions, and once I got expansions, the twin glitch came back.

More bad news. Yes, the batbox creates a "random" number of sims, which it then discards. Unfortunately, it looks like the batbox is using a broken random number generator, so the "random" number of sims is exactly the same every time. The number is only random if the random number generator has been called multiple times since the game was started.

Yikes! Does Pescado know this?


If the random number generator is "called"? What does that mean, exactly.