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Full Summary Methods of Cognitive Neuroscience
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Summary Methods of CognitiveNeuroscience Exam 2021
Disclaimer: I did not include information or a summarization of the articles that included commentary. These
articles were meant as examples and do not include any relevant knowledge or literature for the course. If there
was information mentioned in one of these articles, that was not mentioned in the other literature, I will include
it.
Problem 1: response times and cognitive
architecture
Cognitive psychology and behavioural methods
Cognitive psychology is the study of mental activity as an information processing problem.
Cognitive neuroscience is a distinctive study of brain and behaviour that combines paradigms
developed in cognitive psychology with methods employed in neuroscience; the study of brain
structure and function.
A basic assumption in cognitive psychology is that we do not directly perceive or act in/on the world,
our perceptions, thoughts and actions depend on internal transformations or computations.
Mental representations
Mental representations can take on different forms and the context helps determine which format is
most useful.
Michael Posner introduced the letter-matching task which demonstrates that even with simple
stimuli the mind derives multiple representations: two letters are presented simultaneously, the
perceiver has to judge whether they are both vowels, both consonants or a consonant and a vowel.
In one specific version there are 5 conditions:
1. Physical identity→ 2 letters are the same
2. Phonetic identity→ 2 letters have the same identity but one is capitalized and the other is
not
3. Same category→ both are vowels
4. Same category→ both are consonants
5. Different category→ 2 letters from different categories
For the first 4 conditions the 2 letters are from the same category, yet the response latencies differ
significantly: people respond fastest to physical identity, then phonetic identity and slowest to the
same category, especially when both are consonants.
These results suggest we derive multiple representations of a stimulus: first we look at physical
aspects, then identity and lastly category.
According to Posner these differing response latencies reflect the degree of processing. In this task
the primary dependent variable is reaction time (RT) and experiments using RT use the chronometric
,methodology. This is essential for cognitive psychologists because mental events occur rapidly and
efficiently.
Internal transformations
Taking action often requires that perceptual representations be translated into action
representations in order to achieve a goal. Information processing is not simply a sequential process
from sensation to perception to memory to action; memory and attentional constraints alter how we
perceive something.
Characterizing transformational operations
Sternberg introduced an experiment task where participants have to compare sensory information
with representations that are active in memory. On each trial the participant is presented with a set
of letters to memorize, then a single letter is presented and the participant has to decide whether
the letter was part of the memorized set.
The primary dependent variable is RT and Sternberg postulated that in order to fulfil the task,
participants engaged in 4 primary mental operations:
1. Encode
2. Compare
3. Decide
4. Respond
The recognition process might work in one of 2 ways:
1. A highly efficient system simultaneously compares a representation of the target with all
items in the set
2. The recognition process can only handle a limited amount of information at any point
RT data could distinguish between these 2:
➢ If the comparison process occurs simultaneously→ parallel process; RT should be
independent of the number of items in the set
➢ If the comparison occurs sequential→ serial process; RT should slow down as the set
becomes larger
Results supported the serial process hypothesis; RT increased linearly. Although memory comparison
appears to involve a serial process, much activity in our mind operates in parallel.
Reicher discovered the word superiority effect: an experiment in which a stimulus is shown briefly
and participants are asked which of the 2 target letters was present. The stimuli can be actual words,
nonsense words or letter strings. The critical question centres on whether context affects
performance.
The word superiority effect refers to the fact that participants are more accurate in identifying the
target letter when stimuli are words, suggesting we do not need to identify all letters of a word
before we recognize it.
Representations corresponding to the individual letter and to the entire word are activated in
parallel for each item. Performance is facilitated because both representations can provide
information as to whether the target letter was present.
,Constraints on information processing
Whenever a constraint is identified, it is important to ask whether it is specific to the system under
investigation or if it is a more general processing constraint. Processing constraints are defined only
by the particular set of mental operations associated with a particular task. Exploring limitations in
task performance is a central concern for cognitive psychologists.
A colour-naming task was invented by Stroop, called the Stroop task: a participant is presented with
a list of words and asked to name the colour of each word as fast as possible. it demonstrates the
multiplicity of mental representations.
The stimuli in this task activate 2 separable representations:
1. Corresponds to the colour of the stimuli
2. Corresponds to the colour of concept associated with each word
The activation of a representation based on a word rather than the colour of the word appears to be
automatic. The effect persists for hours after practice, however, the interference from the words is
markedly reduced is the response requires a key press rather than a vocal response.
Reaction time (RT)
Measuring mental processes
Reaction time is the time between stimulus presentation and response.
History
Dutch physiologist Fransiscus Donders wrote an article on the durations of mental processes, based
on measurements of reaction time. This type of research became popular with the advent of
cognitive psychology; mental processes do not seem to have physical properties but they have one→
the time they occupy.
Donder’s subtraction method:
Construct 2 tasks that differ only on a single component of processing and measure reaction times in
both→ subtract the RTs, the outcome is the duration of that single component. If we substitute RT
with voltage in EEG or the BOLD-signal we have the basis of much modern functional brain imaging.
Donder’s is considered the founding father of the discipline mental chronometry: the study of the
organization and timing of mental processes.
Reaction time definition
One trial: a participant is presented with either letter A or B and is asked to press a button with the
left finger when A appears and with the right finger when B appears.
Reaction time can be defined in 2 ways:
1. Operationally: RT is the time interval between stimulus onset and the overt response to that
stimulus
a. Extra assumption: the participant intends to be as fast as possible without making
errors
2. Theoretically: the observed average RT should gain validity as a measure of what we aim it to
reflect, i.e. the minimum amount of time needed by participants to produce the correct
response.
, Most researchers rather accept a small proportion of errors than desire perfect performance as to
avoid the risk that the participant takes longer than needed.
Why measure reaction time?
Reliability and orderliness
RT can be regarded as just a variable in experimental psychology and cognitive neuroscience, it
becomes interesting only when it’s sensitive to differences between experimental conditions.
Research showed it’s highly sensitive to even quite subtle differences, and RT results often display an
orderliness encouraging the construction of models on the underlying information processing.
Scale properties
Often the appropriate measurement scale is the ratio which can be directly interpreted in a physical
sense (meaningful 0 point and is linear). It is also sometimes interesting in its own right→ mental
chronometry, in yet again other cases the absolute time itself is relevant.
Sometimes time is not the variable of interest but we still use RT→ used to represent another
physiological variables, a certain arbitrariness applies.
Using RT’s toolkit: measuring established functions
A more pragmatic reason to measure reaction times is that some RT paradigms have been
constructed that have gained at least some validity as measures of specific cognitive functions that
underlie our daily functioning.
These models propose modules involved in performing these specific functions, which inspires brain
researchers and tells them what to look for.
Limitations
➢ If a response can only be given based on information extracted from the stimulus bit-by-bit
we can assume that at the moment of the response all necessary information has been
extracted
➢ If participants are instructed to be as fast as possible, we can assume that RT reflects the
minimum time needed for information extraction
This highlights an inherent weakness; RT only reflects the end product of processing we can only
make inferences about what happens in between.
RTs are predominantly used in experiments where they are between 200-1000ms→ simple tasks are
easier to study than complex tasks. It is plausible that more complex tasks allow more freedom in
how they’re caried out which can cause variations in participants over time and individual
differences, which can be interesting or considered as noise.
Donder’s subtraction method
Donder’s A, B and C-type tasks
Donder’s method is best exemplified by 3 RT tasks:
➢ Task A: simple RT
o One possible stimulus
o One possible response
o Sensory time + motor time= 201ms
➢ Task B: 2-choice RT
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