Week 13 - Measuring People Flashcards
What is reaction time?
The time that passes from the introduction of a stimulus until the response is made
e.g. firing of start pistol is stimulus + runner moving is response
-> so the time that passes between the firing of the starting pistol and the runner starting to move is the reaction time
What are the three components of reaction time?
Perception -> person needs to perceive the stimulus
e.g runner needs to hear the starting pistol
Processing -> brain needs to make sense of what this auditory signal means
Produce response -> time taken to produce response
e.g brain needed to send commands to muscles to initiate the individual to run
What can reaction times tell us?
- Provide an indirect measure of mental processes
-> in research we typically ask people to perform a cognitive task + will measure the time it takes for them to respond
-> looking at how different response times differ as a change of different task conditions
Measuring reaction times can tell us about:
- The nature of mental processes
- The effect different stimuli has on mental processes
Describe Shepard and Metzler (1971) study
Mental rotation of 3D objects
- Ppts had to determine whether the two pictures were of the same object or not
- Found reaction time increased with the angular difference between the two objects
-> the reaction times were longer when the angular difference between the two objects was at its greatest
- Results suggested ppts imagined rotating the object to solve the task
-> reaction time informs us how ppts completed the task
Describe the stroop effect (1935)
- Ppts are asked to state the ink colour of the word (i.e. ignore what the word says)
Two conditions: - Congruent -> ink colour of the word matches the word itself e.g. blue written in blue, yellow written in yellow etc.
- Incongruent -> mismatch between the word and ink colour its written in e.g. blue written in yellow, yellow written in red etc.
- Found reaction times are shorter for congruent than incongruent trials
-> when word + ink colour match, people are quicker to respond - Manipulation demonstrates cognitive inference occurring in the incongruent trials
-> you have to inhibit your response
What are the different types of reaction time experiments?
Simple reaction time -> 1 type of stimulus + 1 type of response
e.g. ppt viewing computer screen + asked to press the X key every time they see a green light flash
Choice reaction time -> more than 1 stimulus + each has its own specific response
e.g. ppt views computer screen + presented with red light and green light, every time they see the red light they have to press the X key and every time they see the green light they have to press the Y key
Discriminant reaction time -> more than one stimulus, but ppt only needs to respond to one
e.g. may be presented woth a yellow light, a red light, a blue light and a green light but their task is to only respond when the green light is shown
What is Positron Emission Tomography (PET)?
- Utilises the fact that the uptake of glucose is greater in active brain areas
- Some preparation is required - a radioactive substance that mimics glucose is injected into the bloodstream
- Active brain areas take up this radioactive substance more readily + it accumulates in the cell
-> computer can use this info to generate colourful images which reflect brain activity/levels of radioactivity
-> images are referred to as PET scans - Greater levels of radioactivity reflect greater amounts of brain activity
What is the subtraction method?
- Requires ppts to complete a control task as well as experimental task whilst inside the scanner
- Control task provides a baseline measure of brain activation
- To understand what brain areas are activated during the cognitive task - baseline activity is subtracted out
Evaluate PET scanning
Strengths:
- Creates relatively high spatial resolution images of the brain
-> techniques ability to capture different brain structures -> to differentiate between different brain areas
Weaknesses:
- Poor temporal resolution
-> techniques ability to capture brain activity in real time
- Individuals are exposed to radioactive substances which limits the number of scans that can be carried out
What is functional magnetic resonance imaging (fMRI)?
- Utilises the fact that active brain areas require more oxygen, thus blood flow increases to these areas
- Perform tasks while in a scanner + head is exposed to a powerful magnet
- Oxygenated blood produces a different signal to deoxygenated blood
- Signals are used to create high spatial resolution images of the brain
Evaluate fMRI scanning
In comparison to PET
Strengths:
- Nothing needs to be injected into ppts
- Offers better spatial resolution
Weaknesses:
- Poor temporal resolution
What is Transcranial Magnetic Stimulation (TMS)?
PET + fMRI can’t determine whether the brain area is crucial in the performance of a task
- Can use evidence from patients to determine whether a particular brain area contributes to the performance of a task
- Used to establish causal effects in non-patient populations
- Coil creates a magnetic field which is applied to scalp + inhibits the area directly below
- By temporarily ‘turning off’ brain areas we can understand their involvement in particular tasks
What is electrocenphalography (EEG)?
- Measures the brain electrical activity
- Electrodes are attached to the scalp -> by fitting an electrode cap to ppts head
-> electrodes serve to detect small changes in voltage - Different waveforms produced reflect different functional states of the brain
-> EEG waveforms - referred to as alpha waves which are high in amplitude
What are event related potentials (ERPs)?
- Researchers are typically interested in EEG waves produced in response to psychological events (e.g. presentation of a stimulus)
- ERPs are effectively average samples of recording taken after the event has taken place or the stimuli has been produced
-> EEG experiment typically consists of a number of experimental trials + researcher would average across these recordings to wash out random effects
-> left with the waveform that is associated with processing that psychological event
ERP components -> peaks observed in the ERP
- Names after their polarity (positive/negative peak) + latency (when they occurred after event had taken place
e.g. P300 and N400
- Typically researchers are interested in how task conditions affect the amplitude and latency of specific ERP components
Evaluate EEG
Strengths:
- Excellent temporal resolution
-> compared to PET + fMRI which offer poor temporal resolution
Weaknesses:
- Poor spatial resolution -> difficult to determine where this electrical activity was generated from
What are psychological tests?
- Offer a way of measuring psychological constructs (e.g. self-esteem, happiness, motivation etc.)
- Psychological constructs are abstractions -> can’t directly measure them in people
- Psychological tests typically consist of a number of items so we can understand what info ppts are basing their answers on
-> range of items included to obtain a more precise response - Items tend to take the form of either being a closed question or statement
-> ppts’ responses are restricted - Psychological scales provide quantitative data about the characteristic of interest
What are two drawbacks to using psychological tests?
- No insight into why a ppt selected their particular response
- Might be difficult for ppts to provide a ‘clear cut’ response
What are two types of response biases?
Acquiescence bias -> refers to the tendency to respond positively to all items
Response bias -> refers to thee tendency to give the same response to all items
How can you overcome response biases?
- Scales typically include a number of positive and negatively worded items to overcome response biases
-> this encourages ppts to read through each of these items carefully and think about their response - Need to reverse score negative-worded items in the analysis
