Background: How quickly can you respond to something? If you are expecting to se
ID: 3040937 • Letter: B
Question
Background:
How quickly can you respond to something? If you are expecting to see a green light, but don't know exactly when it will be turned on, how much time elapses between the light turning green and your response? This is sometimes called simple detection because the only decision you are making is whether the stimulus has appeared. In more complex tasks, you might need to press one button for Stimulus A and a second button for Stimulus B. In that task, there is an additional decision: Not only must you decide that a stimulus has been shown, but you must also decide which of two responses is appropriate.
Debriefing:
What methods did we employ in this experiment?
On each trial of the experiment, a dot appeared after a variable amount of time and you were asked to respond as soon as you detected it.
This task is not really a proper experiment; rather, it is a way of measuring a basic ability. Detection is not instantaneous: it takes time for the information registered by your eyes to be converted and sent on to the brain. Then, it takes additional time, perhaps the largest proportion, for you to decide that the information means that a green circle was seen and therefore you should press the button. Then, it takes additional time for that message to go to your finger. Finally, there is the time it takes to actually move your finger.
What do we predict participants will do? Why?
The graph below plots the time you took to detect the circle as a function of the trial number. Most people should have a response time between about 200 and 300 ms (although this may vary depending on your computer/tablet). In general, response times will be faster on computers with keyboards than on tablets due to the way in which these devices process key presses and taps.
How robust is this effect? Are there limits to this effect?
Even on the most accurate equipments, it is unlikely that people will respond much faster than about 200 ms due to a combination of cognitive and biomechanical constraints.
Results:
The plot shows your response time in milliseconds for each trial. The expected result is that while you might improve slightly with practice, your RT will be more than 200 ms.
Trial Number
RT (ms)
1
350.616
2
308.754
3
300.720
4
296.985
5
296.378
6
296.371
7
296.393
8
296.271
9
296.245
10
296.637
11
297.116
12
296.769
13
296.454
14
296.899
15
297.295
16
297.903
17
297.830
18
297.778
19
298.206
20
295.560
Questions:
1. Explain why this CogLab exercise is termed “detection”, and provide a guess why it is “simple” and not complex.
2. Here is an issue to consider concerning internal validity. Sometimes a participant in this lab has a response time that is less than 100 milliseconds. How might you explain such very short responses? Suppose another experiment had participants say the word “now” as soon as they detected the green circle, and that the response times were between 100 and 200 milliseconds. What would you conclude about the cognitive tasks involved in these two versions of simple detection?
Trial Number
RT (ms)
1
350.616
2
308.754
3
300.720
4
296.985
5
296.378
6
296.371
7
296.393
8
296.271
9
296.245
10
296.637
11
297.116
12
296.769
13
296.454
14
296.899
15
297.295
16
297.903
17
297.830
18
297.778
19
298.206
20
295.560
Explanation / Answer
1. The exercise involves identifying a green circle and showing a response to it by pressing a button. It is termed detection because the participant needs to identify that an event has occured and give a physical affirmation towards it. It is simple because it does not involve any further decision making; there is just a one point plan - see the green circle, push the button. The participants simply register the event that a green circle came up and thereby their response time to the event.
2. One possibility is that the participant might have noticed a pattern as to the repetitive interval of the green circle, and hence pressed just before the expected moment, thus bypassing the actual cognition process. For the experiment when they say the word "now", the response time is considerably reduced in comparison to the one in which a button needs to be processed. If we analyze the breakdown of where the response time gets spent, the eye to brain and brain to motor (finger/ vocal chord) activation remains same. It is the actual processing of doing the assigned task which makes the difference. Hence, the considerably reduced time can only be alluded to the possibility that the process of speech does not take that much longevity as does the process of pushing the finger to press a button
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