How long does the Navon Global-Local Task take?
About 3 to 5 minutes, as listed in the test library.
Attention
Navon Global-Local Task
Also called: Navon letters, hierarchical letters
Measure global precedence and interference between the whole and its parts with large letters made of small letters.
Useful for perception, attention, autism, aging, mood, and individual-differences research.
Run it with participant credits from $0.99 per participant, or any yearly plan. Preview any test free after you sign up.
Attention3-5 minTimed: desktop or laptop with a mouse or trackpadPaid plans and pay as you go
SSSSSSSSSSSSSSSSS
SSSSSSSSSSSSSSS
S
H
Name the large letter, then the small letters
What the participant sees
One trial, screen by screen, with the timings the test uses.
500 ms
A cross
Until a key press, up to 2,000 ms
A large letter made of small letters
- S
- The letter S
- H
- The letter H
One block asks for the large letter and the other for the small letters.
Example stimuli
Taken from the test's own stimuli.
Large H of small H
Congruent: one letter at both levels
Large S of small S
Congruent: one letter at both levels
Large H of small S
Incongruent: two letters
Large S of small H
Incongruent: two letters
Session structure
Practice
8 trials
Large letter
48 trials
Practice
8 trials
Small letters
48 trials
Scores and how they are computed
RT means response time. Mean RTs use correct responses at or after 100 ms.
- Global Advantagems
- Small-letter block minus large-letter block mean correct RT.
- Positive values mean the large letter was named faster
- Global Interferencems
- Incongruent minus congruent mean correct RT in the small-letter block.
- Larger values mean the large letter interfered more
- Local Interferencems
- Incongruent minus congruent mean correct RT in the large-letter block.
- Larger values mean the small letters interfered more
- Large-Letter RTms
- Mean correct response time when naming the large letter.
- Lower is faster
- Small-Letter RTms
- Mean correct response time when naming the small letters.
- Lower is faster
- Accuracyproportion
- Share of test trials answered with the letter at the named level.
- Higher is better
Example dataOne simulated session, scored by the code that scores your study's sessions.
- Large letter539.9 ms
- Small letters577.6 ms
Mean correct response time (ms)
- Global advantage
- 37.7 ms
- Global interference
- 72.5 ms
- Local interference
- 11 ms
- Accuracy
- 95.8%
| Large letter, mean correct response time | 539.9 ms |
|---|---|
| Small letters, mean correct response time | 577.6 ms |
What this task measures
Measures attention to the whole and to its parts. A large H or S is made of small H or S letters. Participants name the large letter in one block and the small letters in the other, pressing S or H.
Core constructs
- Global and local processing
- Selective attention
- Perceptual organization
Research fit
- Perception and attention research
- Within-study group comparison
- Individual differences in processing style
Paradigm overview
The Navon global-local task measures how people attend to a whole shape and to its parts. Each display shows a large H or S made of small H or S letters. In one block participants name the large letter and ignore the small letters; in the other they name the small letters and ignore the large one. The two levels show the same letter (congruent) or different letters (incongruent).
Each trial starts with a 500 ms cross, and the letters stay until a response or 2000 ms. Participants press S or H. Each block shows the four letter combinations equally often, after 8 practice trials with feedback. Block order is drawn from the session's random seed and recorded, and every session runs a recorded random order.
The global advantage is the small-letter block's mean correct response time minus the large-letter block's, so positive values mean the large letter was named faster. Interference is the incongruent minus congruent mean correct response time within a block.
Task design as built
The trial sequence participants see, as the test runs in ConductCognition. Settings a researcher can change are listed below.
- Display
- A large H or S drawn from small H or S letters on a 5 by 7 grid.
- Blocks
- One block naming the large letter and one naming the small letters; the block order is drawn from the session's seed and saved.
- Fixation
- 500 ms.
- Letters
- Stay until a response or 2,000 ms.
- Keys
- S and H.
- Trial mix
- Each block shows the four letter combinations equally often, two congruent and two incongruent.
- Practice
- 8 trials with feedback before each block.
Data you get
Every response is saved as it happens. Download scores for all plans, and every trial on yearly plans or with participant credits.
Trial columns for this test
- phase
- practice or test. Scores use test rows.
- trial_number
- Order of the trial within its phase.
- random_seed
- Seed of the session's trial order, to rebuild it.
- block
- global (name the large letter) or local (name the small letters).
- block_order
- global-first or local-first.
- global_letter
- The large letter: h or s.
- local_letter
- The small letters: h or s.
- condition
- congruent (one letter at both levels) or incongruent.
- correct_response
- The right key for the trial.
- response
- The key pressed, empty when none.
- rt
- Response time in ms from the moment the screen to answer appeared.
- correct
- Whether the key pressed was the right one.
- timed_out
- No key before the time limit.
- anticipation
- A key under 100 ms, too fast to be a response.
Columns in every export
- participant_id
- Short participant code, the same in every file of the study.
- external_id
- Your own participant ID, when you add one.
- test_version
- Task version the session ran.
- scoring_version
- Scoring version the scores came from.
- customization_status
- standard, or scored_modified when the study changed a setting.
- configuration_json
- The task settings the session ran with.
- is_valid
- The session's quality status (scores file).
- quality_primary_reason
- The main reason when a session needs review or is invalid (scores file).
- started_at
- When the session started (scores file).
- completed_at
- When the session ended (scores file).
Quality checks
Each session is marked valid, needs review or invalid, with the reason.
Scored rows: navon_test from the scored run, S or H (chance 50%, balanced in each block) within 2,000 ms, correctness from the letter at the attended level. Below chance invalidates and not above chance is flagged. One key on 90% of answers invalidates when accuracy is not above chance. Missed responses and responses under 100 ms follow the timed-test rule.
No percentile. Scores and quality flags only.
Running this test
Settings you can change
| Setting | Standard | Allowed |
|---|---|---|
| Trials per block | 48 | 24 to 96 |
Yearly plans can change settings within these limits. Free and pay-as-you-go studies use the standard settings.
Need a setting this test does not have?
Devices and languages
- Timed test: participants need a desktop or laptop with a mouse or trackpad. Participant devices
- Task text: English and Italian.
- Available on: Paid plans and pay as you go.
- No percentile. Scores and quality flags only. How norms work
- Recruiting online? See the setup guides for Prolific, Sona Systems, CloudResearch Connect and Qualtrics.
Cite and describe
Methods text, with the standard settings
Participants completed the Navon Global-Local Task in a web browser (ConductCognition task version 1.0.0, scoring version 1.0.0; Navon, 1977), with the standard settings (trials per block: 48). The global advantage was computed as the small-letter block's mean correct response time minus the large-letter block's. Mean response times used correct responses at or after 100 ms.
ConductCognition versions: task version 1.0.0, scoring version 1.0.0. Every export records the versions each session used, for a methods section.
- Navon, D. (1977). Forest before trees: The precedence of global features in visual perception. Cognitive Psychology, 9(3), 353-383. https://doi.org/10.1016/0010-0285(77)90012-3
Source papers
Navon D (1977). Forest before trees: the precedence of global features in visual perception. Cognitive Psychology, 9(3):353-383.
Paradigm sourceAdults
Research FAQ
Common questions about this online cognitive test
What device does a participant need?
Timed test: participants need a desktop or laptop with a mouse or trackpad. The browser must be Chrome, Edge, Firefox or Safari.
What scores does it produce?
Global Advantage, Global Interference, Local Interference, Large-Letter RT, Small-Letter RT and Accuracy. Each session is also marked valid, needs review or invalid, with the reason.
How is the global advantage computed?
Small-letter block minus large-letter block mean correct RT.
How is interference computed?
Incongruent minus congruent mean correct RT in the small-letter block.
Does it report a percentile?
No. Scores and quality flags only.
Which settings can a researcher change?
Trials per block (24 to 96). Settings can be changed on yearly plans; free and pay-as-you-go studies use the standard settings.
Which languages can participants use?
The test's own text is in English and Italian. Italian participant pages come with yearly plans.
Is this a clinical test?
No. ConductCognition is for research use only. It runs, scores and exports the test; clinical interpretation is outside the platform.
Every test: the full test list.
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