What do we measure in perception?
| Detectability | The ability to notice the presence of a stimulus, like hearing a faint beep in a quiet room. |
| Sensory Magnitude | How strong or intense a stimulus feels, such as rating the brightness of a light on a scale. |
| Discrimination | The ability to tell two stimuli apart, like noticing which of two tones is higher in pitch. |
| Adaptation | The change in perception after prolonged exposure, such as colors appearing different after staring at a bright image. |
Aspects of Perception
Detectability:
- Lowest intensity that can still be noticed
- Helps us know what our baseline perception rate is for our senses
- Detection threshold
Sensory Magnitude:
- How strong stimulus feels compared to reference
Discrimination:
- Just Noticeable Difference/ discrimination threshold
- Smallest difference between stimuli a person can detect
Adaptation:
- How our perception changes after exposure to stimuli
Why is measuring perception important?
- Helps us know our sensory limits
- Safety research
- Business & product development
- Discrimination in radiology
- Designing work place environments
Psychophysics
Psychophysics = science of relating physical stimuli to subjective experiences.
Psychophysical methods
Detection thresholds:
- Measured by presenting stimuli at different intensities & asking if people noticed them
- Determines minimum energy needed for detection
- Comparison of sensory abilities across people, environments
Sensory Magnitiude:
- Measured by asking people to rate strength of stimulus compared to standard
- Compressive non-linear relationship
- Subjective ratings differ from actual intensity
Discrimination Thresholds:
- Measured by presenting pairs of stimuli & asking which one is stronger/ different
- Product design & medical diagnosis
Strengths & Limitations of Psychophysical Approaches
Strengths:
- Easy to set up
- High control
- Low cost
- Straightforward data
- Reliable, even with small samples
Limitations:
- Doesn’t map the brain (show which areas are responsible for perception)
- Repetitive tasks lead to participant fatigue
- Need other tools for brain function
When to use:
- Measuring perception directly
- Comparing sensory abilities
- Test how changes in the environment affect detection & discrimination
When not to use:
- If you have RQs focused on brain activity, neural pathways or biological basis of perception
- When you need neuroimaging tools
Main Neuroscience Tools
| EEG | Single – Cell Recording | TMS | MEG | MRI/fMRI |
| Measures electrical activity from the scalp to track rapid brain responses, often used to study timing of perception and cognition. | Uses tiny electrodes to record activity from individual neurons, revealing how single cells respond to specific stimuli, mainly in animal research. | Delivers magnetic pulses to temporarily disrupt or stimulate brain regions, helping reveal causal roles in perception and behavior. | Detects magnetic fields produced by brain activity, offering precise timing and better spatial detail than EEG, but requires specialized equipment. | MRI shows detailed brain structure; fMRI tracks changes in blood flow to reveal which brain areas are active during tasks. |
EEG
Method:
Electrical brain activity at the scalp.
Used for:
- Face Recognition
Strengths:
- Non-invasive
- Safe
- Good temporal resolution
- Widely available & affordable
Limitations:
- Poor spatial resolution
- Many trials needed for reliable results
Single-cell Recording
Method:
Activity of individual neurons.
Used for:
- Animal studies
Strengths:
- cell level detail
- high spatial & temporal resolution
- Gold standard for studying neurons
Limitations:
- Highly invasive
- Big ethical concerns
TMS
Method:
Uses magnetic pulses to disrupt or stimulate brain regions.
Used for:
- Disrupting speech production
Strengths:
- Allows testing for causal role of specific brain regions
- Non invasive
- Effects are temporary
Limitations:
- Can only reach areas just below scalp
- May affect connected areas
- Possible side effects
MEG
Method:
Magnetic fields from brain activity.
Used for:
- Mapping sensory processing
Strengths:
- Excellent temporal resolution
- Better spatial detail than EEG
- Non invasive
Limitations:
- Very expensive
- Needs specialised facilities
MRI/fMRI
Method:
MRI shows brain structure, fMRI shows function via blood flow.
Used for:
- Visualising memory networks
Strengths:
- High spatial resolution
- Non invasive
Limitations:
- Poor temporal resolution
- Expensive
- Not suitable for people with mental implants
Criteria for Comparing Research Tools
- Spatial resolution
- Temporal Resolution
- Invasiveness & Ethics
- Suitability for Population
- Alignment with RQ
