TEST
Visual Search with Interference (VSI)
Visual selective attention and interference control
Ability to locate what matters and ignore distractions. Explains complaints such as “I can’t find things” or “I get lost among papers,” common after brain injury or in multiple sclerosis.
6
LETTERS PER TRIAL
Z
TARGET LETTER
4
CONDITIONS
2
DERIVED INDICES
WHAT THE TEST IS
Finding the target among similar distractors
Inspired by the Neisser (1964) paradigm. The user must respond with the left hand when a group of six letters includes a Z, and with the right hand when it does not.
The stimuli vary across two dimensions: presence/absence of the target and level of interference (rounded distractors — easy — or angular distractors, similar to Z — difficult). This produces 4 conditions that make it possible to calculate two key derived indices: visual search speed and interference control capacity.
HOW IT IS ADMINISTERED
Four search conditions
Target · Low interference: Z present among rounded letters (GODZCQ).
Target · High interference: Z present among angular letters (VWMZEX).
No target · Low interference: No Z, rounded letters (CQUGRD).
No target · High interference: No Z, angular letters (VXWEIM).
WHAT THE TEST MEASURES
Indicators and their interpretation
Correct responses
Correct responses across the four conditions. Global accuracy integrating sustained attention, discrimination, and executive control.
High: good visual search and interference control.
Low: difficulties especially with distractors similar to the target.
Omissions
Stimuli with no response. Sustained attention and activation level.
High: attentional lapses, fatigue, incomplete strategies.
Low: adequate sustained attention.
Commissions
Indicating that the target was present when it was not, or vice versa. Inhibitory control and accuracy.
High: impulsivity or poorly discriminative style.
Low: good response control.
RT in correct responses
Mean time in correct responses. Overall efficiency of visual search.
Slow: difficulties discriminating or exploring.
Fast: attentional efficiency in search.
RT variability
Stability of attentional processing during the task.
High: instability, fatigue, or distractibility.
Low: stable and efficient performance.
Search speed
Derived index. Speed at which a set of stimuli is explored. Comparison between conditions.
Interference control
Key derived index. Difference between high and low interference (ΔRT). Ability to filter distractors that are perceptually similar to the target.
A small ΔRT reflects good attentional filtering; a large ΔRT is typical of frontoparietal involvement or MS.
RT fatigue
Change in RT between the final and initial 25%.
High: fatigue, lower attentional efficiency.
Low: endurance and learning.
Speed-accuracy tradeoff
Relationship between RT and proportion of correct responses.
High: bias toward speed or accuracy.
Low: optimal balance.
REFERENCES
Bibliography
- Neisser, U. (1964). Visual search. Scientific American, 210(6), 94–102.
EXPLORE OTHER TESTS
Related tests
Would you like to administer this test in your practice?
Request a personalized demo and quantify attentional interference control.
