5. Homeostasis and Response (required practical 7 - reaction time)

Question 1

What is this practical?

Answer 1

investigating reaction time of a person

Question 2

What are the steps for the practical?

Answer 2

1. First, person 1 sits on a stool with good upright posture
2. Person 1 then places the forearm of their dominant arm across the table, with their hand overhanging the edge
3. Person 2 holds a ruler vertically. The 0cm mark should be between person 1’s thumb and first finger.
4. Person 2 then tells person 1 to prepare to catch the ruler
5. Person 2 then drops the ruler at a random time
6. Person 1 has to catch the ruler with their thumb and first finger as quickly as possible when it drops
7. Person 2 records the measurement on the ruler that is level with the top of person 1’s thumb
8. Person 1 has a short rest
9. The test is then repeated several times and a mean is calculated
10. Convert person 1’s results into a reaction time using a conversion table
11. At the end, person 1 and person 2 swap roles so that by the end, person 2 has data on their reaction time

Question 3

Why do person 1 and person 2 swap roles (person 1 tests person 2)?

Answer 3

this allows us to see whether the two people have different reaction times

Question 4

What is the independent variable for this experiment?

Answer 4

the person having their reaction time tested

Question 5

What is the dependent variable for this experiment?

Answer 5

the reaction time

Question 6

What are the control variables for this experiment?

Answer 6

• the starting distance between the thumb and the first finger
• the ruler should always be measured at the top of the thumb
• conditions in the room should be kept the same. eg. the lighting and the level of background noise

Question 7

What other independent variables could be investigated in this experiment?

Answer 7

• effect of practise (1 person would catch the ruler a larger number of times)
• the hands catching the ruler (dominant/non-dominant)
• caffeine (drink cola half an hour before the test and compare to normal reaction time)

Question 8

What is the problem with ing cola for the caffeine reaction time test?

Answer 8

• there could be some other chemical in the cola that could be affecting the reaction time.
• so you could use a caffeine-free cola

Question 9

Where must the reaction time test be taken?

Answer 9

In a lab where hazardous chemicals are not normally used