Loving your child's mind: Evidence (Concept Teaching)
A teacher discusses evidence with two students, Alana and Marwa, moving from the basic definition to real examples: underwater births, handwriting revealing character, a candy theft, forensic traces, and traffic predictions. They compare how evidence works differently in science, law, and mystery stories, and learn to judge what makes evidence strong or weak.
Chapters
And this week I wanted to talk about evidence again. Let me see if I can paste something about evidence. Well, first let's, let's have each of you say what you think evidence is. So what is, what is evidence?
Who's going first? I think evidence is a thing that you can just— that you can use to describe if the thing is false or true.
Which is good, and I realize I pasted the definition of evidence about the same time you say it. So did you see the definition that I pasted?
Yes.
Okay. So one or more reasons for believing that something is or is not true. And when do we have to decide if something's true? Do we always Do you automatically know if something's true or not every day or everything that happens? Or when would you need evidence to decide whether or not something is true?
Maybe this probably wouldn't be real, but if you were trying to solve a mystery or something like that, someone did a really big crime, You'd have to have evidence to see like where he went or where— what he or she did.
Okay. Um, Marwa, do you have any examples of when we might need evidence to decide if something is true?
Maybe when there's a lie or a crime.
Okay. Um, in the dictionary definition, there are actually several examples of cases where we might need evidence, or we might use the word evidence. And let's, let's see what you think of these. So the first one is, there is no scientific evidence to suggest that underwater births are dangerous. Do you guys know about underwater births?
No.
So normally most, most women give birth, you know, above, you know, in a hospital without water. But there are actually some people in some cultures where they give birth underwater, like in a bathtub. And so why would somebody say there is, or why would we need evidence to see if underwater births are dangerous or not? Go, Marwa.
Maybe because someone like, after you give birth, like a baby the baby might not survive to get out of the water or something.
Okay. Do you have any more to say on that, Alana?
Um, no, not really.
So I guess Marwa's wondering, I guess some people might think that underwater births are dangerous because, oh my gosh, you're letting a baby underwater. And as Marwa says, maybe it wouldn't, uh, you know, maybe it might not breathe or survive. So would it be surprising to discover that underwater births are safe?
Maybe.
Okay, um, so how about the next one? Is there any scientific evidence that a person's character is reflected in their handwriting? Um, you know, they mean by a person's character?
I think so.
What do you mean? Can you explain it?
Maybe like if you were writing by hand and you were trying to describe a character's personality, then maybe you would write like softer or harder, like harder as in being like more fierce and stuff like that.
Do you think that a person's character is revealed by their handwriting?
Um, no, not always, but in that case maybe.
What do you think, Marwa, is a person's character revealed by their handwriting? Okay, do you think that, um, you— this is something we could study scientifically to see if in fact a person's character is revealed by their handwriting?
Yeah, maybe.
So suppose we had 100 people and we had them all— first we described if they're maybe aggressive or not aggressive, you know, aggressive or passive. Then we see if they write their hand, how they write their signature. Do you think that aggressive people would have more aggressive signatures than passive people?
Yeah.
What do you think, Marwa? Okay, well, this is— does that seem like a scientific experiment to try to figure that out?
Yes, maybe.
Okay, we're kind of involved in a big project to figure out what is science, what does count as scientific, what doesn't count as scientific. And so these are sort of, um, you know, I would say interesting and unusual examples. Here, this is, I think, what similar to what you first said, Alana, uh, regarding a court case. There's only circumstantial evidence against her, so she is unlikely to be convicted. First, do you guys know what circumstantial evidence is in law?
No, I don't.
Do you know it, Marwa? Okay, so, um, circumstantial evidence means evidence about the circumstances. So suppose we'll go to the example of, say, somebody stealing a candy bar out of somebody else's lunchbox. Um, if you actually saw somebody's hand go into the lunchbox grab the candy and pull it out, I would say that's pretty much direct evidence. Does that make sense?
Yes.
But suppose, um, there's a lunchbox in a room, a classroom maybe, and somebody is seen going into the classroom and coming out of the classroom, and later you discover the candy bar is missing. Then you didn't actually see her take the candy, but the circumstances are kind of suspicious. Does that make sense? Yes. So do you think that we should convict people based on circumstantial evidence or only direct evidence?
Direct.
You think only direct, Marwa?
Most of the time, yes.
Okay. How about you, Alana?
Yeah, maybe I agree with Marwa. Maybe most of the time direct, but sometimes if you don't actually see direct but you do see circumstantial evidence, then I think you should Judge them by that.
Um, do you think that we could, um, decide innocent people are guilty based on circumstantial evidence?
If you know they're innocent, no.
Okay. Um, well, this is why circumstantial evidence is tricky, um, because you could imagine— bless you, Alana— you can imagine seeming like somebody is guilty, but maybe they're not actually guilty. So it is tricky, but let's keep going through the examples. The traces of petrol found on his clothing provided the forensic evidence proving he had started the fire deliberately. Um, first, do you know what forensic evidence means?
No.
Um, okay, do you know what petrol is? Maybe we'll start there.
I think so. I think it's like either a gas or like a type of gasoline.
Exactly. It's actually a British term for gasoline. If Sankara was here, he would probably use petrol when we Americans would say gasoline. Marwa, do you say gasoline or petrol or something else in Kenya?
I don't really know.
Okay, no problem. So forensic evidence is evidence used in deciding who did a crime or not. So if there were traces of gasoline on somebody's clothing, would you say— and would you say that could be evidence that they started a fire?
Pour it on his or her shirt.
Yeah. Suppose there was a fire. I mean, in some ways this sounds like a form of, um, circumstantial evidence, that is, maybe we didn't see the person start the fire, but maybe there was a fire and that person was near where the fire started and they had gasoline on their clothing. Um, does that make it seem maybe more likely that he started the fire than if there was no gasoline on his clothing?
Yeah.
Okay, and then here's a new sentence: All the evidence points to a substantial rise in traffic over the next few years. What kind of evidence would lead us to believe there was going to be more traffic, say, in your neighborhood in the next few years? What kind of evidence would be relevant there?
Um, maybe because more and more people are buying cars, more and more people are making cars, and there's more gasoline.
Okay, those are all kinds of evidence that might lead you to think that maybe there will be more traffic in the next few years.
Yes.
What do you think, Marwa? Does— did Alana provide an explanation for the kinds of evidence that would lead you to believe there could be more traffic in the next few years? Okay, then we've got one more. There is increasing evidence that people whose diets are rich in vitamins are less likely to develop some types of cancer. So how could we have evidence that eating vitamins would— or if your diet is rich in vitamins, you're less likely to develop cancer? What kind of evidence would be relevant there?
Well, maybe because some vitamins, if you're eating them, help your immune system, and maybe that immune system protects you from those types of cancer. So you would be less likely to get it.
Okay. What do you think, Marwa?
The same as Alana.
Same as Alana? Okay. So, and just on a technical point, I think something like what you're talking about might make sense, Alana. It's usually not the immune system when we're talking about cancer. But that's okay. People there— some people do think that, say, um, certain vitamins, or maybe a lack of certain vitamins, can change something about your biochemistry so that you're more likely to get cancer. Um, and so, right, you would look and see what is it about these vitamins or lack of these vitamins that might increase the probability you're going to get cancer. Um, so we've went through several different examples of evidence Now that we've talked about several different examples of evidence, can you say more about when and why we might need evidence? You're muted, Alana.
Does the example have to be big or small?
Take your— whatever works for you, doesn't matter. Okay.
Maybe if people kept thinking that you were guilty of something, like if you're in court and you needed, you really, really needed evidence, you and your, you and other people that are defending for you, you really, really needed evidence.
Okay. So in a court, you may or may not need evidence to prove that you're guilty— I mean, you're innocent. You want people to prove you're innocent, presumably, and not that you're guilty. And how about— I think, Alana, you also started in a mystery story. There's evidence in mystery stories. Is that similar to the legal case?
Um, maybe, maybe not.
Okay, why not?
Well, if you were in a mystery story, that, uh, in the mystery stories that sometimes I've read, not all mystery stories you go to court.
I see. But what I mean is, um, so in a mystery story, whether you go to court or not, do you look for evidence to see who did the thing?
Yes.
So that, to that extent, whether you go to court or not Would you say that what counts as evidence is similar?
Yes.
Do mystery stories sometimes rely on circumstantial evidence?
Yeah, sometimes.
Would you say at the end of the day they have to find direct evidence or not necessarily?
Not necessarily, but sometimes.
Do you, do you sometimes figure out who's going to be— who did it based just just on the circumstantial evidence?
Yeah, sometimes.
Okay. And how about scientific evidence? Does it seem like scientific evidence is similar to mystery story evidence, or are they very different?
Um, sometimes, maybe in some cases in what the mystery story is about, and it could be similar or really, really different.
Okay. What if in a mystery story, do you think, would you be convinced in a mystery story if somebody said, look, their handwriting shows that they're a liar, that's why I think they're lying? Would you think that's good evidence in a mystery story or would that not be good evidence in a mystery story?
In my opinion, not really. It doesn't sound that head-on. But maybe it would in some cases.
Suppose somebody showed you a study that showed that you could in fact predict that they had 100 people and they knew that 50 of them were liars and they knew that 50 of them were honest, and every single time the liars had a certain kind of— maybe they crossed their T's in a certain way, and every certain— every single time the honest people crossed their T's in a different way. And then you saw somebody who crossed their T's in the same way that all the liars crossed their T's, would then you think that the handwriting would tell you something about their character?
Yes, it would, at least in a little bit.
Yeah, and by the way, I don't think it's true that liars always cross their T in a certain way, so I think I'm giving you, you know, just an example but probably not a real example. But I think it might be— I guess the question is, could science tell you something about who is more likely to do a crime?
Yes. Maybe.
Okay. How about— this is maybe an easier one. Suppose in order to do a crime, you had to lift something that weighed ah. 200 pounds. Um, do you think that if somebody was really big and strong and could easily lift 200 pounds, that's different than somebody really small and thin and there's no way they could lift 200 pounds?
Like, if— like, if they could lift it, then they're guilty?
Well, or at least if that was a necessary, necessary step in committing the crime, that if they could lift it, it would mean they're more likely to be a suspect than if they could not lift it.
Yes and no, because if that person, that big and strong person, wasn't actually the guilty person and the other one was, he— the other one could have just gotten another big muscly person to pick it up.
Got it. So maybe you, maybe you might say that being big and strong alone is weak circumstantial evidence. And it does make sense to say some evidence is strong and some evidence is weak?
Yes.
So some evidence is pretty compelling. Some evidence is more likely to make you believe that somebody is guilty, and other evidence might be a tiny step in the right direction, but not very strong step in the right direction. Does that make sense?
Yes.
What do you think, Marwa? Is some evidence strong evidence and other evidence is weak evidence? Yeah. Okay. Um, maybe we won't figure out, uh, how— I mean, it's an interesting question to me then. How do we decide if evidence is strong evidence or weak evidence? Is it just like intuition or a guess? How do you, how do you know in a mystery the Because I bet in mysteries sometimes there is strong evidence that's probably the guilty person, and other times there's weak evidence that maybe that person's guilty, but it's not very strong evidence. How do you know if evidence is strong evidence or weak evidence?
Maybe if, like, it isn't something big, or it isn't that Or it isn't, or it's really obvious to do.
Okay. Have you ever decided, or have you ever thought that somebody was going to be guilty in a mystery story and then discovered you were wrong?
Yes.
Do you think the authors deliberately try to trick you like that?
Yeah, maybe.
Do you get better at figuring out when the authors are going to trick you and when they're not tricking you?
Um, kind of, not really.
Okay. Marwa, do you ever read mystery stories? So Alana, maybe you could recommend some mystery stories for Marwa. Do you know any mystery stories you might want to read? Is Lana frozen for you, Marwa? Okay.
I think you have it though.
You froze for a minute, Lana. Can you say it again?
I think Marwa has it. And then I don't really read other mystery stories very much. I usually read like fiction, but I think one other kind of mystery book that I just started to read is called— or it's a series, but the first book that I'm on is called The Maze of Bones.
The Maze of Bones. Okay, well, um, I will see if, uh— Marwa, do you think you would like mystery stories? Do you know what a mystery story is, Marwa? Okay, do you think you would like them? No? Okay, then we won't recommend them if you don't like them. That's cool. All right, in which case, um, we will leave the mystery of strong versus weak evidence for another time. And thanks to you both, and hope you have a good week. Okay, bye.
