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Bio 103, Lab 6, Oneself as a Biological Entity. II. Reacting

Paul Grobstein's picture

In last week's lab, we noticed that a part of oneself (the heart) was influenced by but not fully under the control of other parts of oneself. In this lab, we want to further develop the idea that oneself consists of an array of parts that interact with one another to give what we observe as behavior.

A touch starts signals moving in sensory neurons which eventually cause signals to move in motor neurons which eventually cause muscle contractions and movement. How long does it take to move when one is touched, and why? How much of that time is the time it takes for signals to move from the endings of sensory neurons to the endings of motor neurons? How much of that time is the time it takes muscles to contract and cause movement? That's what we'll be looking at in the first part of the lab, and studying further in the second part

Following the demonstration, you and your team should develop your own questions and observation protocols to explore some interesting aspect of what is going on in reacting. For example, would you expect the time taken to be different if the stimulus occurred at a more distant location on the body? On the same side as the response as opposed to the opposite side? If the response was with your dominant or your non-dominant hand? Would you expect the time to change if you were tired? preoccupied? had recently had coffee? Is it the time that signals take within the nervous system that changes or is it the time for muscles to contract and cause movement? Or both?

Don't try and answer ALL the questions. Pick one (or think up one) that you're interested in and have a guess about. And collect enough data so you have some confidence in your conclusions about that situation. And write up your question/hypothesis, observations, conclusions in the lab forum.

cejensen's picture

Reaction Time (Claire and Valerie)

We did experiments with physiology equipment which measures reaction time. We took turns being the test subject and the tester. The tester would poke the subject in the dominant shoulder, and the subject, upon experiencing the stimulus, would press a button. We first measured our base responses. Latency is the time between stimulus and response.

Test 1
Latency 1: 126 milliseconds
Latency 2: 40 milliseconds
Total: 166 milliseconds

Test 2
Latency 1: 139 milliseconds
Latency 2: 44 milliseconds
Total: 183 milliseconds

Test 1
Latency 1: 420 milliseconds
Latency 2: 37 milliseconds
Total: 457 milliseconds

Test 2
Latency 1: 128
Latency 2: 26
Total: 154

We thought that our times might change when we were distracted. First, the tester asked the subject questions while the subject was trying to respond to the stimulus (as well as the questions). We collected data for this, however, we believe that we collected the wrong data for this, so we will not include it.

Realizing our mistakes from the previous experiment, we tried a new one. The subject would watch a music video while simultaneously trying to respond to the stimulus.

Data from the Music Video experiment:

Latency 1: 107
Latency 2: 93
Total: 200

Latency 1: 380
Latency 2: 53
Total: 433

These are from the same experiment. In the latter instance, in the subject was distracted by an outside factor (people walked in the room).

Test 1:
Latency 1: 176
Latency 2: 23
Total: 199

Test 2:
Latency 1: 122
Latency 2: 26
Total: 148

We found that in some instances the distraction of the music video had more of an impact on the reaction time than others. For the most part, the music videos had very little effect on reaction time. What had more of an impact on our reaction time was outside distractions that we had not anticipated and couldn't control.

Therefore, we think that unanticipated distractions have the greatest effect on reaction time (with the music videos, we anticipated distraction).

By Claire and Valerie

paoli.roman's picture

Music, Teaxting, and our Reaction

For this lab we were experimenting our reaction to an outside force ("poking stick") and how this could be affected by another outside force (music and texting). Our hypothesis was that with increased outside forces the amount of reaction time would increase meaning it would take longer for us to react with comparison to our base. I (Paoli) would listen to music while Laura was texting. Our hypothesis was correct because while we were attempting to concentrate on the main outside force it was difficult to pay attention. For Laura it was more difficult since both of her outside forces dealt with her hand and her reaction was negatively influenced. Thus, the muscles were not given enough time to react and got confused in Lauras case since the sensory neurons were concentrating on two different forces. In my case, Laura would pause in between the outside force ("poking stick") I would get distracted with the music and forget that she was poking me! My muscles did not react at all at times since I was not concentrating and the sensory neurons were functioning towards the other outside force (music).


  Latency 1 latency 2 total latency
paoli 108 179 287
laura 105 150 255
paoli 168 37 205
paoli 582 65 647
paoli 229 60 289
average 326.3333 54 380.3333333
laura 326 23 349
laura 328 41 369
laura 169 58 227
average 274.3333 40.66667 315
Yashaswini's picture

State of mind vs State of surroundings


We wanted to observe factors that affect our reaction time to outside stimuli. What makes us react almost instantly to certain situations, relatively slowly to others, and almost not at all to others? Does reaction or reaction time depend on external factors such as.. level of noice/disturbance, potential distractions, intensity of stimulus, frequency of stimulus etc? Or are internal factors such as.. mental  conditions, state of mind, drug-levels in our body (caffeine, nicotine etc) equally responsible?


Yashaswini's data:



With music

On phone

Latency 1




Latency 2




Total Latency




 Michelle's data:

Avg Latency 1:


Avg Latency 2:


Total Latency



On comparing Yashaswini's base trial with Michelle's, we notice that while Michelle's total latency was 193 ms, Yashaswini's was only 50ms! :O

This increased when Yashaswini was checking her voicemail to 84ms, which was still significantly lower (less than half!)  than Michelle's base trial!

It also further increased when we played loud music. Total latency increased to more than double of that during the base trial, to 118ms.



We concluded that Yashaswini's response time was FREAKISHLY HIGH, during all the trials, ALL the time, she is probably in the state of mind where her defenses are up, and she is conscious of every tiny thing that could.. threaten/hurt her. This could be because of.. a high level of adrenaline in her blood. Or this could be as a result of a high amount of caffeine-intake. Either way, her responses were far quicker than Michelle's responses, that were closer to the class average that approxiamtely lay between 150-200ms.

However, even though Yashaswini's responses were really FAST compared to others, we did observe variations within her.. "unusual" range. Talking on phone was a distraction and her mind was occupied doing other things, such as.. dialing numbers, paying attention and responding to what the other person has to say etc. This is probably what slowed down reaction time.



ktan's picture

Kristel Jesse & Sophie

Our group set out to find how different irritants on the lungs affect our reaction time. In order to measure this Sophie and Kristel each smoked a cigarette, and then measured their reaction times, and Jesse held his breath during the actual experiment.

BASE (average)
                   Latency 1          Latency 2          Total Latency
Jesse             144.2                  36.4                   180.6
Sophie           122.2                    62                    184.2     
Kristel            104.4                  29.8                   134.2         

                   Latency 1          Latency 2          Total Latency
Sophie           130.4                   54.8                  194.2
Kristel            100.6                    34                    134.6     
Jesse             242.8                   28.8                  271.6

We noticed that for all of these irritants our average reaction time increased. However Kristel's reaction time only went up by .4, however Kristel's reactions had been extremely consistent throughout both the base and the experiment. Jesse's reaction may have been so extreme because the lung duress was tied directly to physical duress.

Wil Franklin's picture

Latency Traces



Latancy Traces






Kalyn's picture

Testing the Effects of Sight on Reaction Times

Kalyn & Karina

Hypothesis: How does the sight affect reaction rates? We predicted that using your sight will give you a faster reaction time because your body is anticipating the shock and therefore is primed to send the electrical signals to the brain.

T1 = Time to Muscle activity

T2 = Time to button press

T3 = Time from muscle activity to button press.

Touch knee with dominate hand while eyes are closed

Experiment #1

T1 = 0.255

T2 = 0.310

T3 = 0.055

Experiment #2

T1 = 0.251

T2 = 0.295

T3 = 0.044

Experiment #3

T1 = 0.304

T2 = 0.325

T3 = 0.021


Close Eyes

Experiment # 1

T1 = 0.242

T2 = 0.265

T3 = 0.023


Experiment #2

T1 = 0.216

T2 = 0.242

T3 = 0.026


Experiment #3

T1 = 0.198

T2 = 0.230

T3 = 0.032


Open Eyes – Look directly at experimenter

Experiment #1

T1 = 0.127

T2 = 0.273

T3 = 0.146


Experiment #2

T1 = 0.102

T2 = 0.268

T3 = 0.166


Experiment #3

T1 = 0.110

T2 = 0.265

T3 = 0.155

Conclusion: We found that the time from muscle activity to button press, our T3 results, showed faster response times when the participant’s eyes were closed rather than when they were open. We feel this is because using your sight creates more distractions for the body to process since it must account for multiple stimuli and the added shock. This makes opening your eyes result in a slower response time while closing the eyes primes the body for a response.

When your eyes are closed you can directly focus on the sensation and therefore the electrical signal of the shock can be relayed to the brain at a faster pace. Besides sight other factors could be taken into consideration which would also affect the reaction time of an individual. These factors include sobriety, fatigue, hunger and other things.  Since factors vary greatly among individuals this would account for the large class differentiations result times found. 



dchin's picture

Relationship between Reaction Time and Distance

For our lab, we hypothesizes that the closer the point of contact is to your brain, the faster the reaction time is.  We think that by having the point of contact closer to the brain, the exchange between the brain and the point of contact is shorter.  The brain then relays the message to press the button to your hand much faster.  
Methods:  We decided to pick the arm and the foot as points of contact because the arm is closer to the brain and to the hand pressing the button and the foot is the furthest point from the brain. 
We decided to test the arm first. We conducted three trials.
Trial 1
t1 = .179s
t2 = .252s
t3 = .073s
Trial 2
t1 = .16s
t2 = .355s
t3 = .195s
Trial 3
t1 = .106s
t2 = .174s
t3 = .068s
The average time from muscle activity to button press was .112s.
Then we tested the foot. We, again, conducted three trials.
Trial 1
t1 = .103s
t2 = .245s
t3 = .142s
Trial 2
t1 = .142s
t2 = .406s
t3 = .264s
Trial 3
t1 = .183s
t2 = .257s
t3 = .074s
The average time for t3 was:  .16
Our hypothesis was proven incorrect. Our conclusion is that there is not a correlation between reaction time and distance. We expected that the reaction time for the arm would be faster that the reaction time for the foot. However, it is possible that this is due to human error. Also, we wonder if perhaps the position of our body would affect out reaction times. For example, maybe having your arm or foot in different positions would result in different reaction times. Another factor that may have affected our results is that Debbi was expecting the stimulus, so she might have pressed the button prematurely, which also would have affected the results.
-Debbi Chin and Herman Marcia

drichard's picture

i have a better reaction time than stu - david

For this lab we focused on the question of whether or not the origin of a stimulus affected reaction time. After fixing electrodes to the participant's dominant thumb, we poked the participant in the calf, knee cap, and stomach. We recorded the time that elapsed between the poking stimulus and the button-pressing reaction, as well as the time between the poking stimulus and muscle action. Using these two values we were able to calculate the time elapsed between muscle action and the instant of button-pressing. Each participant was subjected to two trials (two calf, knee, and stomach pokes, respectively). We took the average time elapsed between (t1) poking stimulus and button-press, (t2) poking stimulus and muscle action, and (t3) muscle action and button-press.

Our results are as follows:


Calf: t1=.1325 s, t2=.192 s, t3=.0595 s

Kneecap: t1=.149 s, t2=.214 s, t3=.065 s

Stomach: t1=.155 s, t2=.219 s, t3=.064 s


Calf: t1=.1775 s, t2=.2205 s, t3=.043 s

Kneecap: t1=.188 s, t2=.2395 s, t3=.0515 s

Stomach: t1=.174 s, t2=.214 s, t3=.040 s

We standardized stimulus on the same side (if the participant was right handed, we poked their right calf, their right knee cap, and the right side of their stomach) and we made sure the participant kept his/her eyes closed. This was meant to control for the variable of anticipation. The participant did not know when he/she was going to be poked and thus could not "prepare" for a more swift reaction.

Initially our hypothesis was that the distance between the origin of stimulus and the brain would increase the reaction time, but our data proved inconclusive on this point. On the whole, it was hard to isolate a trend between the two sets of data. One thing we did notice is that Julia's t3 (the time elapsed between muscle activity and button-press) was consistently lower than David's t3. We hypothesize that this is a result of David having a larger thumb muscle; because the muscle is composed of more cells the orchestration required to press the button would take longer.

Further testing would, of course, be necessary, due to the nature of experimenting on complex organisms such as humans.

Also, it is worth noting that Julia actually had the fastest reaction time recorded, with a t1 time of .098. Do not be fooled by our title.


Terrible2s's picture

Handedness and reaction times

We tested the variability of handedness. First we tested the standard (dominant hand, eyes closed, knee stimulous on the same side) for each of us (we are both right-handed). Then we tested handedness by doing 6 trials per person, 3 on each hand. We did the trials poking the same side as the button was in - but on our arms instead of our knees - and with our eyes open. Our results were as follows:


Lili - t1 = .144, t2 = .166, t3 = .022

Halima - t1 = .142, t2 = .179, t3 = .037

Median reaction times:

Lili (left hand) - t1 = .075, t2 = .128, t3 = .053

Lili (right hand) - t1 = .086, t2 = .115, t3 = .029

Halima (left hand) - t1 = .049, t2 = .076, t3 = .027

Halima (right hand) - t1 = .046, t2 = .064, t3 = .018

First, we observed that the standard reaction times are higher for the stimulus to the muscle activity and the stimulus to the button press. We think that this can be attributed to the fact that, in the handedness trials, we were watching the stimulus be applied and the stimulus was located closer to the button press.

We found that our data showed a subtle trend that the time from muscle activity to button press was slightly longer for our left hands. We didn't notice any differences in the time from the stimulus to the muscle activity or the time from the stimulus to the button press, however. It would have been helpful to conduct more trials to see whether or not these are true trends.

-Terrible2s and Lili


mfmiranda's picture

Lab 6

In this lab we wanted to figure out whether our ability to see the stimulus affected the response time.


t1- time until muscle activity

t2- time until button is pressed

t3- t2 - t1 - time from muscle activity until button is pressed


Subject 1

Eyes closed

t1 = .111

t2 = .15

t3 = .039


Eyes Open

t1 = .048

t2 = .077

t3 = .029


Subject 2

Eyes Closed

t1 =  1.768

t2 = 1.83

t3 = .062

Eyes Open

t1 = .078

t2 = .122

t3 = .044


Subject 3

Eyes Closed

t1 = .097

t2 = .172

t3 = .075


Eyes Open

t1 = -.023

t2 = .049

t3 = .072



At the end of our experiment we realized that during the second trials, when our eyes were open, we had negative times. This was because when the person could see what was about to happen, there wasn't muscle activity, but the muscles were getting ready to move. Because of this the time between the stimulus and the time when the button was pressed was much shorter. We had predicted that this would happen, since being able to see what would happen, would mean that the person was anticipating, and would then react sooner, and maybe even prematurely.


The time between when there was any muscled activity and when the button was actually pressed was also much shorter during the second trials when our eyes were opened. We thought that this might mean that there was some sort of visual component. This would mean that somehow the message was related more quickly when it was done visually than when all we had to rely on was feeling the stimulus.


Maria, Mariah, Heather