TIME TO RESPOND TO GRABBING A RULER

Practical analysis of the time it takes to capture a falling object can provide an estimate of how different persons have various reflex response capacities. Studying the likelihood that someone will actually prevent a falling object from hitting the earth is incredibly fascinating. This activity's goal was to learn how one person's reflex differs from the next. In order to conduct the experiment, a sample of fourteen people was chosen, and the reaction times of each were recorded.
The findings demonstrated that although there is an average time for halting falling objects, various individuals actually caught the falling ruler at various intervals. This was an indication that some people are highly responsive to reflex reactions while others have too weak response capabilities. Examination of the results indicates that from the taken sample a correlation coefficient of 0.1831 between the distracted case and the undistracted one exists. Throughout the experiment, the subject maintained normalcy to ensure that there was no exaggerated outcomes. The subjects were able to go through the experimentation and their reaction times obtained respectively.

Objectives

To investigate the distance a body travels while falling before a person can grab it.

To show that different people have different rates of reflex reaction.

Theory

Human beings have a complex structure that can be studied independently in biology as a response. As Purves et al., (2008) notes the structure is composed of nerve endings at the epidermis of the skin, endings attached to body organs, and endings attached to the bones. The endings act as sensory receptors that enable the five common senses in human beings to effectively work. Reception of sensory reactions is transmitted by hyperpolarization of the synaptic membrane to the spinal cord or the brain, depending on the interpretation of the received signal. For reflex senses, the spinal cord is usually used because it is the first sensory interpretation organ that receives the sensory impulse.

This experiment is objectively used to investigate the reflex interpretations of sensory impulse that occur when someone has to grab a falling object. The investigation seeks to answer the questions; what is the time lapse after photoreceptors sense a falling object and send an impulse to the spinal cord? For how long does the object keep falling until a coordination is done between the photoreceptor and the psychomotor reaction to grab the object? The reaction time is calculated using the formula:

Reaction time = Square root of distance, d

490

Where d is the distance the ruler slides between the fingers before the participant stops it from falling. The SI unit here is cm/s2. This reaction time is the basis of establishing how fast an individual’s reception and reaction to the stimulus is.

Procedure

Apparatus

A meter rule, 14 volunteer subjects.

Diagram(s)



Diag. 1



Method

The first subject was asked to hold their hand such that the thumb and the index finger extended by 8cm away from each other. A metric ruler was held by the experimenter, such that it was vertical and between the thumb and the index finger of the subject as shown in the diagram; dig 1 above. The initial mark coinciding with the top of the hand was made to be the 0cm mark of the ruler. A count, up to three, was done to alert the subject and the experimenter on the release time of the ruler. The subject was expected to react by grabbing the ruler after the 3rd count. The time taken to grab the ruler was to be calculated later as reaction time.

The distance, d, through which the ruler fell between the two fingers before the subject grabbed it was recorded. The results were tabulated. The experiment was repeated on each of the fourteen subjects under the following circumstances; when the subject was distracted, and he or she was using their dominant hand, the highly probable value, and the highly improbable value. The highly probable value was obtained when the dominant was used in the experiment while the highly improbable value obtained when the non-dominant hand was used. The results were tabulated in table 1 shown in the results.















Data presentation and analysis

Results.

Table1: Raw data and its analysis on reaction time to grabbing the ruler

Subject serial

Dom Avg (x1) in cm/s2

NonDom Avg (x2) in cm/s2

X= (x1 + x2)

2

DomDistracted (y)

a = (x-x)

b = (y-y)

A

14.0

11.3

12.65

19.7

1.014

-0.243

B

12.3

13.0

12.65

13.0

1.014

-6.943

C

10.0

6.7

8.35

9.0

-3.286

-10.943

D

5.7

12.3

9.00

32.3

-2.636

12.357

E

13.3

8.6

10.95

42.3

-0.686

22.357

F

11.5

8.2

9.85

24.3

-1.786

4.357

G

8.0

7.7

7.85

19.0

-3.786

-0.943

H

9.6

8.0

8.80

12.6

-2.836

-7.343

I

10.2

11.5

10.85

25.3

-0.786

5.357

J

7.0

6.0

6.50

12.3

-5.136

-7.643

K

21.3

20.7

21.00

15.0

9.364

-4.943

L

15.7

23.2

19.45

27.7

7.814

7.757

M

22.0

12.3

17.15

21.0

5.514

1.057

N

8.0

7.7

7.85

5.7

-3.786

-14.243









Data Analysis

T-test for the data

Mean of x = Sum of x = 162.9 ÷ 14 = 11.636 cm/s2

No. of subjects

Mean of y = Sum of y = 279.2 ÷ 14 = 19.943 cm/s2

No. of subjects

The mean of x and y are significantly giving the expected results. When a person is distracted, it is expected that concentration towards a particular event lowers. For that reason, the reaction time is expected to drop, which the average of y clearly indicates. The average reaction time of x is shorter than that of y indicating that this T-score has a p-value approximated to be about 0.02 due to normal human errors.

Correlation coefficient.

Sum of ab

(Sum of a2) x (Sum of b2)

Rxy = = 106.488 ÷ 581.576 = 0.1831.





Sum of ab = 106.488, sum of a2 = 266.320, sum of b2 = 1270.017

Values of a×b, a2 and b2 have been calculated and substituted in the correlation formula. This indicates that the correlation coefficient of undistracted response to grabbing the falling ruler against the distracted situation is 0.1831.

The graph of correlation is shown in graph 1 below.



Graph 1. A graph of scatter plot of x and y values

Discussion

From the tabulation above, the values obtained when the person is not distracted were taken as x1 and x2 and their average taken as x while the value obtained when the subject is distracted was regarded as y. The correlation of the two variables, x and y is done to know how distraction of the subject causes a shift, away from the average when the subject is not distracted. The figures show that there is a great departure from the undistracted situation to the distracted one (Hazewinkel, 2001).

The correlation coefficient has, in this case, been obtained as positive, this implies that both values of x and y increase together. Since the value is neither zero nor ±1, the correlation actually exists but it is not perfect.

Conclusion

To conclude, the objective of the practical has been met since it has explicitly shown that there is correlation between distraction and undistracted response. Although response has varied from one person to another, the T-score has confirmed the possibility of existence of this correlation coefficient. From the scatter plot graph, the distribution of values is extremely spread out for the distracted case. For the undistracted, the values are consistent and uniformly around the average expected value. This draws another conclusion that there is an average reaction time that is expected in order for someone to sense and react against a certain stimulus.































References

Hazewinkel, M. ed (2001)[1994]. Students’ test, Encyclopaedia of Mathematics. Springer+Business Media B.V/ Kluwer Academic Publishers.

Purves, D., Augustine, G., Fitzpatrick, D., Hall, W., LaMantia, A., McNamara, J., & White, L. (2008). Neuroscience (4 ed). Sinauer Associates, Inc. p207.



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