Unit 11 Sensing the Environment

Topic

What are the factors affecting reaction time?

Curriculum Link

11 Sensing the Environment (Responses to stimuli)

Estimated Lesson Time

40 minutes

Introduction

Reaction time is the time between our senses receiving a stimulus and making a response to that stimulus.  Reaction time plays a significant role in our everyday life, in some cases a long reaction time will lead to tragic outcomes.  When a driver sees a jaywalking pedestrian in front of his moving car, the visual stimulus that he receives will be sent to the brain for processing and then makes a response to the muscle to brake the car.  If the driver's reaction time is long, a traffic accident may occurr.  A shorter reaction time is thus life saving.

A simulation of braking a car to test reaction time can be carried out in the following websites:

[English version] http://www.phys.hawaii.edu/~teb/java/ntnujava/Reaction/reactionTime.html
[Chinese version] http://www.phy.ntnu.edu.tw/oldjava/Reaction/index.html

In most situations a long reaction time might not as fatal as a traffic accident, but surely you would prefer a shorter reaction time in other situations, such as when you are playing a computer game.

Key Question

A short reaction time, in general, is beneficial and significant.  What is/are the factor(s) that affect one's reaction time?

Learning Objectives

In this activity, the students should be able to

  1. recognize that the brain interprets sensory signals;
  2. explore some factors affecting reaction time;
  3. acquire planning and designing skills (SP3) in designing an experiment to measure reaction time;
  4. acquire measuring skills (SP1) and experimenting skills (SP4) in measuring reaction time;
  5. acquire interpreting data skills (SP5) in analysing the data collected;
  6. acquire communicating skills (SP6) in presenting the data systematically.

Teaching Plan

Task (Time) Brief Description Materials Objectives

Engagement & Explanation
(5 min)
  • Teacher lets students play a simulation of braking a car and from this brings out the importance of a shorter reaction time.
  • Teacher shows a light plastic ruler to elicit students to suggest ways to measure reaction time without using a stop watch
  • Teacher shows a conversion graph to find out reaction time for a given distance a ruler falls and let students know that scientific investigation sometimes needs to use tables or graphs from a databook
  • Teacher shows a blindfold to elicit students to suggest possible factors that affect reaction time. Discuss with students whether a blindfolded person requires a longer reaction time to grasp a falling ruler.
  • A plastic ruler and a blind fold
  • A graph of reaction time against distance fell
(1)

Exploration
(15 min)

Students identify possible factors that affect reaction time and design setup(s) to measure reaction time accordingly.

Possible factors are:

  • With vs Without a countdown
  • Blindfolded vs Not blindfolded
  • Trained vs Not trained
Students carry out the experiment with different variables		 (2), (3) & (4)

Evaluation
(10 min)

Students analyse the set(s) of data

   (5)

Explanation
(10 min)

Students present the data, the conclusion and explain how they reach the conclusion

   (6)