Ruler Lab - Part One

In this lab, you will be measuring your reaction time in response to a falling object. Under a constant acceleration (gravity = g ), the average velocity is gt/2 (time = t), if the starting velocity is 0. Distance (d) is related to acceleration and time by the following equation:

d = V(av.)t or (gt/2)(t) = (gt2/2)

For the purposes of this lab, you will be measuring the distance (how far the ruler falls before you catch it) and solving the above for time.

Aconversion table for converting distance to time has been provided for you, so you don't have to calculate it yourself!
 

Here is how you measure your reaction time:

  1. Find a ruler and a partner (preferably a fellow Intro to Psych student).
  2. Person 1 holds up ruler lightly between 2 fingers, preparing to drop ruler. Hold ruler vertically.
  3. Person 2 prepares to catch the ruler between thumb and index finger (keep them about 1 inch apart) at the bottom edge of the ruler, without touching the ruler.
  4. Person 1 says "ready" and drops the ruler within the next 2 seconds. Person 2 will catch the ruler as soon as person 1 lets go of ruler, using thumb and index finger.
  5. Look at the ruler right where Person 2 caught it--this is the distance (in inches). You can convert this distance to time (in milliseconds) using the conversion table.
  6. Try this a few times until you are comfortable with this procedure.

Activity:
  1. First, try the catch with your writing (dominant) hand. Record distance and convert to time using the table. Do the same with your other (non-dominant) hand. These values will serve as baseline values to which you can compare your consequent performances.
  2. Experiment 1: Learning
    Do the catch 8 more times using your writing hand. Record distance and calculate reaction     time.

Question 1: Does your reaction time improve with practice ?   

     3.  Experiment 2: Transfer
          Now, do the catch once using your other (non-dominant) hand. Repeat this trial 8 more               times. Record distance and calculate reaction time using the conversion table.

Question 2: How does the reaction time for your other hand (a) improved compared to its baseline value and (b) compare to the last time for your writing hand?   
  1. Experiment 3: Focusing on the Stimulus vs. the Response
If the initial of your last name is A thru L do (a) first, (b) second. For initials M thru Z, do (b) first and (a) second.

(a) Stimulus:
Person 2: focus your attention on the ruler, and the moment it is released by person 1. Do this 3 times, and calculate the mean reaction time for the 3 trials.

(b) Response:
Person 2: focus your attention on the movement you will make for catching the ruler. Do this 3 times, and calculate the mean reaction time for the 3 trials.  

Question 3: Which was faster, focusing on the response or stimulus?

Question 4: How do the results of this lab support (or not support) the mechanist-vitalist issue discussed in class?

Turn in:

  1. One plot of all of the learning and transfer trials (with trial number on the x-axis and reaction time on the y-axis), and a second graph with the stimulus and action trials. The same graph can have multiple lines.  Create one line for each type of trial with each reaction time value recorded as one point on the line. The line may not be straight (this will depend upon your rate of improvement).
  2. The answers to the 4 questions.
  3. Comments on the plot, if you find anything interesting



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