This lesson is called Human reaction time: practical and is from the unit Coordination and control: the human nervous system.

Hi there, my name's Mrs. McCready and I'm here to guide you through today's lesson.

So thank you very much for joining me.

In our lesson today, we're going to predict, plan, and carry out an investigation into the effect of a factor on human reaction time and analyse the data to draw a conclusion.

We're gonna come across a good number of keywords in our lesson today.

They're listed on the screen there for you now.

Pause the video if you want to make a note of them, but I will introduce them to you as we come across them.

Now, in our lesson today, we're going to first of all plan our investigation, then we're going to carry out the investigation before we draw a conclusion.

So you're looking forward to it.

I hope so.

I hope you're ready to go as well.

I know I am.

So let's get started.

So we know that organisms must be sensitive to their environment in order to be considered to be a living thing.

So this goes back to MRS GREN or MRS C GREN about movement, respiration, sensitivity and so on, the features that make an organism able to be considered living.

Now, in humans, we have a nervous system as part of the things that we use to monitor our environment and sense any changes to it.

And the nervous system monitors both the external environment, so what's happening around outside our body and also changes that are happening within our body.

And these changes are monitored and fed back to and help us to control our responses to our environment.

Now we can see how quickly we can respond to changes in our environment by measuring our reaction time.

Now, some people who have very particular jobs, such as racing drivers and tennis players and sprinters all deliberately practise to improve their reaction time so that it is as fast as possible.

So racing drivers can react as quickly as possible on the road around other drivers.

Tennis players can respond very, very quickly to fast hit balls coming towards them, and sprinters can get off the mark as soon as the gun is fired.

And these are just a few examples.

So it's possible to improve your reaction time with practise.

But our reaction time can also be changed by other factors.

So there's plenty of other things that can slow us down or speed us up, make us more responsive or less responsive.

So what do you think they might be? What are the factors might increase or decrease our reaction time to things? So you might have thought things like tiredness or how awake you are feeling, how old you are, whether you've had any caffeine or drunk tea or coffee or Coca-Cola or something like that.

Whether you've taken any drugs, either medicinal or illegal, whether you've had any alcohol to drink, and whether you are subjected to any distractions in your environment, whatever they might be, lots of different things might distract us.

So these are all things that might increase or decrease our reaction time.

So what of these do you think might impact our reaction time? Caffeine, background noise, tiredness, and how old you are, which do you think will impact your reaction time? I'll give you five seconds to think about it.

Okay, so caffeine will impact your reaction time.

So will background noise.

So will tiredness and so will your age.

Did you get them all right? Well done.

So what you're gonna do is, you're gonna work with a partner and you're gonna investigate the effect of a factor on your reaction time.

So they are going to drop a ruler without telling you and you are going to catch it.

And the distance that the ruler falls before you catch it will give you an indication of your reaction time.

The shorter the distance, the faster your reaction.

The key is, you have to catch the ruler without knowing that it's going to fall.

So you're going to investigate the impact of a factor on your reaction time.

So you could change for instance, the brightness of the room and see if that has an impact on how quickly you can catch it.

But whatever we choose to change, we have to be ethical in our decision, because we are ultimately experimenting on a living organism, us.

So we must be ethical.

So what do you think might be ethical? Ethical is about being moral and right and looking after the health and welfare and the morality of the situation of the individual involved.

So a good ethical choice is something that is right and proper and good for that person or that organism and is not gonna cause them harm.

So what might be an ethical factor that you can change within the classroom? So it's possible to acceptably and ethically change factors such as: The time of day that we're conducting the experiment.

Whether or not the person catching the ruler is concentrating on something else, such as standing on one leg at the same time as trying to catch the ruler.

Or other factors along those lines.

The problem with the time of day is that's really quite difficult to orchestrate within the school day.

So we need to choose something which is a bit more practical as well.

It is less acceptable, ethically speaking, to make our subject consume a fizzy drink or a drink which contains caffeine or lots of sugar in it, because this has a risk of harming their health and therefore that would be unethical.

So for this experiment, we're going to change which hand is used.

What happens to your reaction time when you are catching the ruler with your left hand versus your right hand? So let's just check this.

In experiments involving living organisms, we must be ethical in our approach.

True or false? True or false? So that is true, but why? Is it because living organisms can be easily harmed or is it because living organisms might lodge a complaint against us? What do you think? So this is because living organisms can be easily harmed.

Well done.

Now, with all experiments, there are variables that need to be changed, measured, and controlled.

So let's look at what these are.

So the independent variable is the variable that we're choosing to change.

The dependent variable is the one that we are measuring.

And the control variables are variables that we need to keep the same across all of the experiments.

So what are these for this experiment? Can you think what might be the independent, the dependent, and the control variables in this experiment? Well, hopefully you've identified that the independent variable is the hand that we are using, whether we're catching with our dominant hand or our not dominant hand.

The dependent variable is the distance that is caught on the ruler.

And the control variables will include things such as the ruler itself, the initial position that the ruler is aligned to your fingers, the person who is doing the dropping.

So you've got the same person doing the dropping each time.

The time of day that you are investigating this at and the number of practise attempts you're allowed before you start.

And there may be other control factors that you might have thought about as well.

So what I'd like you to do is to make a prediction on the effect of the factor.

So a scientific prediction is a testable statement about the possible outcome of the experiment.

So you need to think about: Which hand is going to have the fastest reaction time? Is it going to be your dominant hand, that's the one that you use to write with and you use most often, or is it going to be your non-dominant hand, your other hand? So let's just check again.

How many independent variables can there be in a valid experiment? One, two, three or more? I'll give you five seconds to decide.

So hopefully you've said that there can only be one independent variable.

This is the variable that we are choosing to change in a valid experiment.

So what I'd like you to do is to plan your experiment before you go on.

I want you to write a prediction for your investigation: which hand do you think will have the fastest reaction time? I'd like you to complete the table to list the variables within the practical.

So describe what the independent, the dependent, and the control variables are and give an example for each of them for this practical.

And I'd like you to write a method that you could follow to collect the data for your investigation.

So pause the video and come back to me when you are ready.

So you should have written a prediction for your investigation.

Which hand do you think will have the fastest reaction time? And you might have said that your dominant hand will have the fastest reaction time.

You might have predicted something different, but hopefully you've said that.

Then I asked you to complete the table to list the variables within the practical.

So you should have said that the independent variable is the one that is being changed, and this is the hand that is being used to catch the ruler.

The dependent variable is the one that is being measured, and this is the distance that the ruler falls before you catch it.

And the control variables are the ones that are kept the same across all of the experiments.

And this includes things like the ruler, the person dropping the ruler, the time of day and the number of practise attempts.

But you might have included some other examples for this practical as well.

Then I asked you to write a method that you could follow to collect the data for this investigation.

And your method should be ethical, so you are not harming your participant.

It should describe what the test subject and the person dropping the ruler will do and when.

It should describe the apparatus that you are going to use.

It should describe which measurements you are going to record and how many times you're going to repeat the test.

So just check over your work, make sure that your method does contain those various different points.

Well done.

Right.

Let's move on to carrying out the investigation.

So you are going to work with a partner in order to complete this investigation.

The subject is the person who is catching the ruler and the experimenter is the person who is dropping the ruler.

So the first thing you need to do is stand up with the experimenter holding the ruler firmly, with the 0 cm end aligned with the top of the subject's thumb and forefinger.

So you need to have your thumb and forefinger sort of clasped bit like that as I'm showing you in the video.

And then have the ruler position between the thumb and the forefinger at the very top of the hand aligned with the zero centimetre mark.

Then without any countdown, but when you are both ready, so the person who's going to be doing catching should tell the experimenter that they are ready, and then at some point relatively soon after that the experimenter will need to drop the ruler, let it go, just let it go, don't throw it or anything, just let it fall, and the subject needs to catch it as quickly as they can.

So you're gonna have to practise that to make sure that you're both coordinated, you know how to drop the ruler, you know how to catch it and that your positioning within your hand is all good and stable enough.

So practise it a couple of times.

And then on the third attempt, record the distance at which the ruler was caught.

Then repeat that four more times before you change hands so that essentially you are collecting five pieces of data.

So in order to make sure that your measurements are accurate and repeatable, you need to make sure that you keep the noise down within the classroom and avoid distractions so that both of you, both the experimenter and the subject, can concentrate.

You also need to make sure that the ruler is properly aligned to the fingers before every drop.

And you also need to allow the subject to declare when they are ready so that the experimenter knows when it's good to go and can drop the ruler at some point shortly after that point.

If you follow those instructions and the method, you hopefully will get accurate and repeatable results.

So to make the experiment a fair and reliable test: should the experimenter state when you are ready to start, should the top of the ruler be aligned with the bottom of the hand, should the room be quiet and free from distractions? What do you think? I'll give you five seconds to think about it.

Okay, so you should have said that the room should be quiet and free from distractions.

Remember, it is the subject who is stating when they're ready to start.

And remember, the zero centimetre part of the ruler should be aligned with the top of the hand.

So what I'd like you to do now is to carry out the investigation and record your results in a table.

So pause the video and come back to me when you are ready.

Okay, so you should have carried out your investigation And your results might be a bit like these results that I've put up on the screen here with different measurements for the left hand compared to the right hand.

Okay, so let's now draw a conclusion from the data that you've collected.

So you've measured the distance that the ruler fell, and now you can, firstly, identify and remove anomalous results, then calculate a mean reaction distance in centimetres, then convert that using the conversion table into a reaction time in seconds.

So the first thing you need to do is remove anomalous results because anomalous results will skew the mean.

Now, anomalous results are data points that are unusually high or low when compared to the other values in your data set.

So looking at the sample data for instance, we can see that test 4 on the left hand is very low compared to the other values and test 1 on the right hand is also very low compared to the other values on the right hand.

So we can ignore those values, remove them from our dataset before we then go on to calculate the mean distance.

Now, you might not have any values like this because you might have ignored that measurement and simply not recorded it.

But if you have recorded them, then identify them and remove them from your dataset.

So now we've removed that anomalous data, we can calculate the mean.

So we're going to calculate the mean of the left hand data by adding the left hand non-anomalous values together, then dividing by the number of values we've added.

So in this case for the left hand mean we're going to add 17 and 15 and 13 and 16, then divide that by 4 to give 15.

25, and then we can repeat that with the right hand data to calculate the mean for the right hand.

So that's 10 plus 7 plus 8 plus 11 all divided by 4 to give a value of 9.

We can add those values into our table, rounding them to the nearest centimetre.

So that's 15 centimetres for the left hand and 9 centimetres for the right hand.

They're our mean values.

Now we've got our mean values.

We can now convert the distance into a reaction time using the conversion table.

So for the left hand it was 15 centimetres, so that's a reaction time of 0.

175 seconds.

And for the right hand that was 9 centimetres and that's a reaction time of 0.

136 seconds.

We can add those reaction times into our results table and then we can work out what this all means.

So we can see that there is a difference between the mean reaction times for each hand.

My dominant hand, my right hand is faster at reacting to the falling ruler than my left hand.

And I expect you'll find a similar result that your dominant hand is able to react faster than your non-dominant hand.

Now, we could improve those reaction times through extensive practise, but the reason the dominant hand is faster than the left hand is because you use it more.

By using your hand more you are developing muscle nerve connections within the hand muscles, which means that the muscle responses can be controlled faster and they can be more accurate as well.

Also, the neural connections within the brain are more developed for your dominant hand than your non-dominant hand and that also will mean a faster response.

So because you are using that hand more often, those connections both within the hand itself and also within the brain are just much more developed, which is why your reaction time is faster with your dominant hand.

So let's review that then.

Which data points should you ignore? Mean values, calculated values or anomalous values? I'll give you five seconds to decide.

Okay, so you should be ignoring anomalous values.

These are the odd values which are lying well outside the general range of the other data that you've collected.

So finally, I'd like you to draw your conclusion.

I'd like you to cross through anomalous data in your results and then calculate mean distances for both your left and right hand values and record those mean values in your table to the nearest centimetre.

Then use the conversion table to convert your reaction distance into a reaction time and then record those values in your results table as well.

Then I'd like you to compare your reaction times for your dominant and non-dominant hands.

Which one gives the fastest reaction? Can you add a brief explanation as to why this is likely to be the case? So pause the video, come back to me when you've finished analysing and concluding your data.

Okay, so you should have crossed through any anomalous data and then calculated the mean distances for your left and right hands.

Then use the worksheet conversion table to convert your reaction distance into reaction time.

Then I asked you to compare those reaction times, decide which hand gives a faster reaction and add a brief explanation as to why this is likely to be the case.

So you should have said that your right hand is dominant over your left hand or maybe the other way around, and that therefore your right hand had a faster reaction time than your left hand.

Obviously, if you are left-handed than it would be the other way around.

In your dominant hand, reactions are faster because the nerve-muscle connections are more developed and the neural connections in your brain are more established as well.

So check over your answer.

Have you included those points and have you said your dominant hand over your non-dominant hand? Well done.

I hope you enjoy comparing your reaction times to, both, against each of your hands, but also against your partner as well.

It's quite interesting.

Were you similarly matched? I wonder.

So in our lesson today, we've seen that the reaction time is a measure of how fast we can respond to changes in our environment.

And this can be affected by a number of different factors.

Now we can predict and test our reaction time and the effect of changing a factor by dropping a ruler and measuring the distance taken to catch it.

Now, in our practical, we identified the variables in this experiment and we decided how best to control them to ensure a fair test.

And we also saw how it's important to be ethical in our practise when we are using living organisms to ensure their safety and wellbeing.

We also saw that it is our dominant hand that has a faster reaction time than our non-dominant hand and some of the reasons why that is.

So I hope you enjoyed our lesson today and you've learned about your reaction speed as well.

Maybe you can go away and improve that, maybe you've got a really fast reaction time.

Thanks very much for joining me and I hope to see you again soon.

Bye.