L9 - Mental Chronometry and Simple Decisions Flashcards
1
Q
How was the speed of human mind determined before psychology?
A
- Through introspection
- Thought mind was infinitely fast and unanalysable
- Then thought if not infinite, then it far too fast to be measured
- But NOW nerve conduction has finite speed
2
Q
How to work out nerve conduction velocity?
A
- Obtained first direct measure of NCV in frogs
- Dissected frog to expose nerve attached to leg muscle = measure the delay between electric stimulation of nerve and contraction of nerve
- Changed stimulation in point A and B
- Found that the conduction velocity was between 25-30 metres/sec
3
Q
What were follow up experiments in humans?
A
- People have a weak electric shock to limited space of skin like toe
- When shock is felt = asked to carry out a specific movement with hand/teeth interrupting the time measurement ASAP
- Tested on toe and thigh by working out the distance between toe/thigh and divided by RT of toe minus RT of thigh
- We know RT of nerves depends on a lot more than distance
- Most RT are within range of 10-100ms
4
Q
Why do we use RT?
A
- Marker of mental processing speed
- Allows movement of philosophy to psychology: more objective measurement
- Varies with many things e.g intelligence, memory, neurodegeneration, learning, motivation, attention, fatigue and depression
5
Q
What is the relationship between age and RT?
A
- Time taken for ppts to step on a nintendo wii board
- Females have a systematic higher RT slightly
- As we age, RT gets higher
6
Q
What is mental chronometry?
A
- Using reaction time to study structure and function of mental processes
- The subtraction method - Donders, 1868
7
Q
What did Donders do?
A
- Can compare across tasks
- Task A = press button when light seen= simple RT = detection and execution
- Task B = press button 1 when yellow light, and button 2 when blue light = detection, identification = selection = execution (slower than task A as more processes)
- Task C = press button 1 when yellow light and nothing when blue light = detection, identification, execution
8
Q
What does Donders subtraction method allow?
A
- We can infer speed/time of internal mental processes, which is not directly observable
- Relies on two strong assumption
9
Q
What is the first assumption?
A
- Serial processing
- Processes are arranged sequentially: output of one serves the input to the next e.g detection leads to identification etc.
- At a given time, only one process can be active: non-overlapping in time, each process takes a certain amount of time, RT is the sum of the durations of all processes
10
Q
What was the experiment of serial processing? (Miller 1982)
A
- Have 4 potential stimuli: S/T in upper/lower case
- Use left hand if S and diff fingers for big/small and right for T, or control: left is S/t and right is s/T
- Same hand letter is faster: consistently faster RT
11
Q
Why is the same hand letter faster?
A
- Hyp1: selection stage is shorter because the stimulus-response mapping is easier to remember BUT should go away with blocks as you should see a benefit as you get used to one condition, but there is not
- Hyp2: Hand selection can start before finger selection = response selection can start before all info is processed - brain finds it easier to distinguish between letter than size e.g you see S, you pick between middle/index finger, can pre-select hand = wait much later to identify before you can select = identification is longer
- Stages can be done parallel, benefit Is stable over time
12
Q
What is an alternative model to serial processing?
A
- Cascade processing: rather than being strictly sequential, info may flow continuously from one process to next = overlap
- e.g faster to identify letter, than size then vowel, then selection of hand/finger
13
Q
What is the second assumption?
A
- Pure insertion
- Stage can be added or omitted to a sequence of processes, without altering other processing stages e.g whether or not a stimulus needs be to identified does not affect the later execution stage
14
Q
What is an evaluation of pure insertion?
A
- In simple and choice RT tasks: also measure response force
- Force can probe the execution process, if pure insertion is true the execution should not change between task
- BUT exp found that response force varies between task, what you do before has an impact on execution
15
Q
What is the additive-factor method?
A
- Factor: an IV with different values/levels
- Additive: test if two factors have additive effects on RT
- Can infer existence of independent processing stages
- If two factors which effect on Rt is additive = parallel lines on graph (no interaction) = factors selectively affect two independent stages
- If factors interact = we do not know if we have two independent stages
- In a factorial design = if effects are additive on RT = factors affect different stages, if effects interact = factors affect at least one common stage
- Does not rely on the assumption of pure insertion: change IV within same task
- Allows to test the independence of processing stages but still assumes serial processing
16
Q
What is the application of additive-factor method? (Study)
A
- If ppts select 1 or 4: press right or otherwose press left
- Stimulus encoding, response selection and selection
- Factor 1 = stimulus quality: how easily read: intact or degraded
- Factor 2 = Memory set size - how many numbers do you press with one hand
- Very additive factors
17
Q
What is the application to MDD patients?
A
- MDD patients have slower RT
- Can this be attributed to impairments to stimulus identification or response selection or both: choice RT task
- Had a detection stage where there was a strong/weak signal and then selection with left/right hand as well as if it was compatible/in e.g if signal is on right, press with right hand
18
Q
Results of application MDD patients
A
- MDD group suffers more from incompatibility of stimulus-response mapping
- MDD likely affects response selection
- Within each group, effects seem additive
