VisionNCT06933693
Mixed Vs Blocked Search: Four Unique Tasks
A study testing Mixed trials and Blocked Trials in people with Vision and Healthy, run by Brigham and Women's Hospital at 1 site in United States.
Trial summary
The goal is to look for qualitative differences in visual search behavior when one search is performed many times in a row compared to when multiple search tasks are intermixed. Four search tasks are tested. In the Mixed condition, the four tasks are randomly changed from trial to trial. Read more about this study
- Who is it for?
- Ages 18 years and olderHealthy volunteers can take part
- What is being tested?
- Mixed trials and Blocked Trials
- Type of treatment
- Lifestyle or therapy programme
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 40 participants
- Where
- 1 siteUnited States
- Study dates
- 1 Jun 2024to 30 Jun 2029
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- Pass Ishihara color vision test
Who cannot join
- vision less than 20/25 with correction
- history of neuromuscular or visual disorders
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
United States1 site, 1 recruiting
- Recruiting
Brigham & Women's Hospital
Boston, Massachusetts, 02116
Cailey Tennyson, BA, 617-525-3681, ctennyson1@bwh.harvard.edu
Jeremy M Wolfe, PhD, 617-851-1166, jwolfe@bwh.harvard.edu
About this study
Official title: Prevalence Effects in Visual Search: Theoretical and Practical Implications
The goal is to look for qualitative differences in visual search behavior when one search is performed many times in a row compared to when multiple search tasks are intermixed. Four search tasks are tested. In the Mixed condition, the four tasks are randomly changed from trial to trial. In the Blocked condition, each task is run as a block of 100 trials.
Read the detailed description
NOTE: This registration is linked to a Human Subjects registration in ASSIST. That, in turn, is part of an NCI Grant, R01EY017001. The grant describes many proposed experiments and notes that many others might be done as follow-up studies. At the suggestion of the NIH, the investigators grouped these studies into several "studies", each covering multiple experiments. The experiment described here is part of Aim 1 of R01EY017001. It is not possible to register a set of experiments through the PRS system in CT.gov and it is not possible to file an annual report for the grant (RPPR) without an NCT number for projects that have started collecting participants. Accordingly, the investigators are describing one experiment here that would be part of the "Project 1" bundle of studies.
When scientists study visual search in the lab, they usually ask people to do dozens of instances of the same type of task in a block. (e.g., Please find a vertical line….in the next 100 trials). However, in many (maybe most) visual searches in the real world, the participants are rarely looking for the same item (or same type of item) back-to-back. You do one search. Then the participants do another, and so on. (Find the jam. Now, find the bread. Now find a knife, etc). We want to know if the investigators would get the same results if the investigators mixed different searches together as the investigators do when the investigators test in long blocks of one specific type of search. This is important because the investigators want to know if the rules, established by years of blocked experiments, continue to apply in the more mixed real world.
There are multiple variants of this mixed/block experiment. In Experiment 1, observers are trained on four different search tasks. Then they perform 400 trials in the Mixed condition and the Blocked condition. In the Mixed condition, the four tasks are randomly changed from trial to trial. In the Blocked condition, each task is run as a block of 100 trials. Stimuli are placed in random locations in a jiggled 5 x 5 grid. The grid are placed within square field that is 0.5 of the maximum height of the screen. Each stimulus item fit into an invisible box that is 0.11 of the screen height. If the viewing distance is about 60 cm, a standard computer screen would show a stimulus field of about 15 deg on a side and each item would be placed in a box of about 3 x 3 deg. The background is white. Trials are divided evenly between three set sizes: 8, 16, and 24 items and evenly between target-present and absent trials. Stimuli are presented until the observer responds by pressing either 'p' or 'q' to indicate target present or absent, respectively. Accuracy feedback is provided after each trial.
- Being tested
- Mixed trials, Blocked Trials
- Keywords
- visual search, visual attention
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Mixed trialsBehavioural
All tasks will be randomly mixed in a single block of 400 trials.
Blocked TrialsBehavioural
Each search task will be presented in a block of trials.
| Study group | Role | What they receive |
|---|---|---|
| Blocked Trials | Experimental | There are four search tasks in this experiment. Each task will be presented in a separate block of 100 trials Receives: Behavioral: Blocked Trials |
| Mixed Trials | Experimental | There are four search tasks in this experiment. All tasks will be randomly mixed in a single block of 400 trials. Receives: Behavioral: Mixed trials |
What is being measured
The primary outcome is the main question the study is designed to answer.
Response Time (RT)
How long it takes to respond that the target is present or absent.
Measured: Through study completion, an average of one year
Secondary outcomes (1)
Accuracy
The rates of false positive and false negative errors
Measured: through study completion, an average of one year
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted18 Apr 2025
- Study start1 Jun 2024
- Primary completion1 Jun 2029 (estimated)
- Study completion30 Jun 2029 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for VisionStudies of the same condition, open and under way.
- More trials run by Brigham and Women's HospitalThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Sequential
- Model description
- Each observer will do 400 "mixed" trials and 400 "blocked trials.
- Masking
- None (open label)
- Enrolment
- 40 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Brigham and Women's Hospital
- Sponsor type
- University, hospital or other
- Collaborators
- National Eye Institute (NEI)
- Responsible party
- Principal investigator, Jeremy M Wolfe, PhD, Brigham and Women's Hospital
- Investigators
- Jeremy M Wolfe, PhD, Principal investigator, Brigham and Women's Hospital
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06933693
- Sponsor's protocol ID
- 2007P000646-G
- Other IDs
- R01EY017001
- Status last verified
- Aug 2026
- First submitted
- 11 Apr 2025
- Last updated
- 19 Aug 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Yes: We will share de-identified information about age, sex, and individual data
Study at a glance
From the registry record, last updated by the sponsor on 19 Aug 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Prevalence Effects in Visual Search: Theoretical and Practical Implications
- ClinicalTrials.gov ID
- NCT06933693
- Acronym / sponsor ID
- 2007P000646-G
- Keywords
- visual search, visual attention
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 40 participants (estimated)
- Lead sponsor
- Brigham and Women's HospitalUniversity, hospital or other
- Collaborators
- National Eye Institute (NEI)
- Study start
- 1 Jun 2024 (actual)
- Primary completion
- 1 Jun 2029 (estimated)
- Study completion
- 30 Jun 2029 (estimated)
- First posted
- 18 Apr 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The goal is to look for qualitative differences in visual search behavior when one search is performed many times in a row compared to when multiple search tasks are intermixed. Four search tasks are tested. In the Mixed condition, the four tasks are randomly changed from trial to trial. In the Blocked condition, each task is run as a block of 100 trials.
Detailed description
NOTE: This registration is linked to a Human Subjects registration in ASSIST. That, in turn, is part of an NCI Grant, R01EY017001. The grant describes many proposed experiments and notes that many others might be done as follow-up studies. At the suggestion of the NIH, the investigators grouped these studies into several "studies", each covering multiple experiments. The experiment described here is part of Aim 1 of R01EY017001. It is not possible to register a set of experiments through the PRS system in CT.gov and it is not possible to file an annual report for the grant (RPPR) without an NCT number for projects that have started collecting participants. Accordingly, the investigators are describing one experiment here that would be part of the "Project 1" bundle of studies.
When scientists study visual search in the lab, they usually ask people to do dozens of instances of the same type of task in a block. (e.g., Please find a vertical line….in the next 100 trials). However, in many (maybe most) visual searches in the real world, the participants are rarely looking for the same item (or same type of item) back-to-back. You do one search. Then the participants do another, and so on. (Find the jam. Now, find the bread. Now find a knife, etc). We want to know if the investigators would get the same results if the investigators mixed different searches together as the investigators do when the investigators test in long blocks of one specific type of search. This is important because the investigators want to know if the rules, established by years of blocked experiments, continue to apply in the more mixed real world.
There are multiple variants of this mixed/block experiment. In Experiment 1, observers are trained on four different search tasks. Then they perform 400 trials in the Mixed condition and the Blocked condition. In the Mixed condition, the four tasks are randomly changed from trial to trial. In the Blocked condition, each task is run as a block of 100 trials. Stimuli are placed in random locations in a jiggled 5 x 5 grid. The grid are placed within square field that is 0.5 of the maximum height of the screen. Each stimulus item fit into an invisible box that is 0.11 of the screen height. If the viewing distance is about 60 cm, a standard computer screen would show a stimulus field of about 15 deg on a side and each item would be placed in a box of about 3 x 3 deg. The background is white. Trials are divided evenly between three set sizes: 8, 16, and 24 items and evenly between target-present and absent trials. Stimuli are presented until the observer responds by pressing either 'p' or 'q' to indicate target present or absent, respectively. Accuracy feedback is provided after each trial.
Study design
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Sequential
- Masking
- None (open label)
- Number of arms
- 2
- Model description
- Each observer will do 400 "mixed" trials and 400 "blocked trials.
| Arm | Type | Receives |
|---|---|---|
| Blocked Trials | Experimental | Behavioral: Blocked TrialsThere are four search tasks in this experiment. Each task will be presented in a separate block of 100 trials |
| Mixed Trials | Experimental | Behavioral: Mixed trialsThere are four search tasks in this experiment. All tasks will be randomly mixed in a single block of 400 trials. |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (1 listed)
- Pass Ishihara color vision test
Key exclusion criteria (2 listed)
- vision less than 20/25 with correction
- history of neuromuscular or visual disorders
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Mixed trialsAll tasks will be randomly mixed in a single block of 400 trials. | Behavioural | Mixed Trials |
| Blocked TrialsEach search task will be presented in a block of trials. | Behavioural | Blocked Trials |
Primary outcome
Response Time (RT)
Time frame: Through study completion, an average of one year
How long it takes to respond that the target is present or absent.
1 secondary outcome
Accuracy
Time frame: through study completion, an average of one year
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 19 Aug 2026.
- Individual participant dataSharing planned: Yes. We will share de-identified information about age, sex, and individual data
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Jeremy M Wolfe, PhD principal investigator
Brigham and Women's Hospital
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Mixed trials and Blocked Trials in people with Vision and Healthy, run by Brigham and Women's Hospital at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 1 inclusion and 2 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 19 Aug 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Jeremy M Wolfe, PhD (6178511166, jwolfe@bwh.harvard.edu), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Response Time (RT) (time frame: Through study completion, an average of one year). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 19 Aug 2026.