Pro/Antisaccade Task

Version: v1 (current)

An oculomotor control paradigm measuring inhibitory control and voluntary gaze redirection.

Overview

The Pro/Antisaccade task is a powerful measure of inhibitory control and executive function using eye movements. In prosaccade trials, participants look toward a suddenly appearing peripheral target (reflexive, prepotent response). In antisaccade trials, participants must inhibit this reflexive urge and instead look in the opposite direction (requiring cognitive control).

Antisaccade errors (looking toward rather than away from the target) reveal failures of inhibitory control. Error rates and latencies provide sensitive measures of executive function. The task requires minimal instruction and can be adapted for populations with limited verbal abilities, making it valuable for clinical and developmental research.

The task is widely used in neuropsychiatry (schizophrenia, ADHD, Parkinson's), aging research, and cognitive neuroscience studies of prefrontal cortex function.

Scientific Background

Classic Findings:

Antisaccade Cost: Antisaccades are slower (50-100ms) and more error-prone (5-20% errors in healthy adults) than prosaccades
Inhibitory Failure: Errors reflect failure to suppress reflexive saccade toward target
Error Correction: Many antisaccade errors are self-corrected within 100-200ms
Age Effects: Children and older adults show higher antisaccade error rates
Clinical Markers: Elevated errors in schizophrenia (40-50%), ADHD, frontal lobe damage

Key Mechanisms:

Reflexive Suppression: Inhibiting automatic saccade toward sudden onset
Voluntary Generation: Programming saccade to mirror location
Response Conflict: Competition between pro and anti responses

Seminal Papers:

Hallett (1978): Primary and secondary saccades to goals
Munoz & Everling (2004): Look away: The anti-saccade task and the voluntary control of eye movement
Hutton & Ettinger (2006): The antisaccade task as a research tool in psychopathology

Why Researchers Use This Task

Executive Function: Sensitive measure of inhibitory control and response suppression
Clinical Biomarker: Endophenotype for schizophrenia and other neuropsychiatric disorders
Aging Research: Track age-related decline in cognitive control
Prefrontal Function: Probe dorsolateral prefrontal cortex and frontal eye fields
Pharmacology: Test effects of medications on cognitive control

Current Implementation Status

Fully Implemented:

✅ Prosaccade and antisaccade blocks
✅ Left/right target locations
✅ Error rate and latency measurement
✅ Practice trials for each condition
✅ Self-reported saccade direction (in absence of eye-tracker)

Partially Implemented:

⚠️ Manual keyboard/button response instead of eye-tracking
✅ Per-trial gap/overlap (set the Gap (ms) column per trial; 0 = overlap)

Not Yet Implemented:

❌ Eye-tracking integration for true saccade measurement
❌ Error correction detection
❌ Mixed block variant (pro and anti cued trial-by-trial)

Configuration Parameters

The Pro/Antisaccade configuration exposes a small set of global display/behaviour options. Timing (fixation, gap, cue, target, ITI) and eccentricity are per-trial values set in the trial spreadsheets (see Trial Spreadsheet below), not global parameters.

Display Options

Parameter (form key)	Type	Default	Range	Description
`pro_antisaccade_fixation_size_px`	number	20	5–50	Size of the central fixation cross (px)
`pro_antisaccade_cue_size_px`	number	20	5–50	Size of the peripheral cue (px)
`pro_antisaccade_fixation_color_hex`	string	`#000000`	—	Fixation cross color (hex)
`pro_antisaccade_cue_color_hex`	string	`#000000`	—	Peripheral cue color (hex)

Behaviour Options

Parameter (form key)	Type	Default	Description
`pro_antisaccade_time_based`	boolean	true	When on, each trial auto-advances on timeout (target window) and keyboard responses are collected. When off, on-screen Left/Right buttons are shown.
`pro_antisaccade_practice_enabled`	boolean	true	Whether the practice phase (with feedback) runs before the main block.

Trial Spreadsheet

Main and practice trials are defined as spreadsheet rows. Each row has the following columns:

Column	Type	Description
Trial Type	dropdown	`prosaccade` or `antisaccade`
Side	dropdown	`left` or `right` (cue side)
Block	text	Free-text block label (optional)
Fixation (ms)	numeric	Fixation duration (min 100, default 1000; default rows use 500)
Gap (ms)	numeric	Gap between fixation offset and cue onset (min 0, default 0; default rows use 200)
Cue (ms)	numeric	Peripheral cue duration (min 50, default 200; default rows use 100)
Target (ms)	numeric	Response window after cue offset (min 50, default 1000)
ITI (ms)	numeric	Inter-trial interval (min 0, default 1000; default rows use 500)
Eccentricity (deg)	numeric	Cue distance from center in degrees (default 10; default rows use 8)

Keyboard Shortcuts

Researchers can customize the keyboard bindings used during the task:

Parameter	Type	Default	Description
Show keyboard hint	boolean	True	Display an on-screen hint showing the configured keys
Left key	key	Arrow Left (←)	Key for left response
Left action label	text	"Left"	Label shown in the keyboard hint for the left key
Right key	key	Arrow Right (→)	Key for right response
Right action label	text	"Right"	Label shown in the keyboard hint for the right key

Data Output

Markers

The runtime emits, per trial: a slug-prefixed trial-start marker (pro_antisaccade_trial_start, or pro_antisaccade_practice_trial_start in the practice phase), fixation_onset/fixation_offset, gap_onset (only when the trial's gap is > 0), cue_onset/cue_offset, target_phase_start (opens the response window; latency is measured from here), and a trial-end marker. Practice trials additionally emit feedback_shown.

Example cue_onset marker:

{
  "type": "cue_onset",
  "ts": "2024-01-01T00:00:01.000Z",
  "hr": 1234.56,
  "data": {
    "trial_index": 0,
    "is_practice": false,
    "stimulus_id": "pro_antisaccade_0_1",
    "trial_type": "antisaccade",
    "cue_side": "right",
    "expected_response": "left",
    "block": "main",
    "cue_ms": 100
  }
}

Response Data

Each response is recorded as a trial-grain row (the source enum is keyboard, button, timeout, or moderator_advance):

{
  "trial_index": 0,
  "is_practice": false,
  "stimulus_id": "pro_antisaccade_0_1",
  "source": "keyboard",
  "trial_type": "antisaccade",
  "cue_side": "right",
  "expected_response": "left",
  "response_value": "left",
  "raw_key": "ArrowLeft",
  "response_correct": true,
  "responded": true,
  "block": "main",
  "latency_ms": 285
}

Summary Artifact

Emitted as pro_antisaccade_summary_<taskIndex>.json:

{
  "task_kind": "pro_antisaccade",
  "task_index": 0,
  "total_trials": 24,
  "overall": {
    "total": 24,
    "valid_responses": 22,
    "correct": 18,
    "accuracy": 0.818,
    "mean_rt_ms": 285,
    "mean_correct_rt_ms": 270,
    "timeouts": 2
  },
  "breakdowns": {
    "trial_type": {
      "prosaccade": { "total": 12, "valid_responses": 12, "correct": 11, "accuracy": 0.917, "mean_rt_ms": 245, "mean_correct_rt_ms": 240, "timeouts": 0 },
      "antisaccade": { "total": 12, "valid_responses": 10, "correct": 7, "accuracy": 0.7, "mean_rt_ms": 325, "mean_correct_rt_ms": 300, "timeouts": 2 }
    }
  },
  "effects": {
    "antisaccade_cost_ms": 60
  },
  "trials": [...]
}

When practice is enabled and practice trials were run, a practice object (same shape: total_trials, overall, breakdowns.trial_type, trials) is also included.

Example Research Configurations

Standard Pro/Antisaccade

Blocks: Prosaccade (30 trials), then antisaccade (30 trials)
Timing: 1000ms fixation, immediate target onset, 1000ms target display
Locations: ±10° left/right
Analysis: Antisaccade error rate, RT cost

Gap Paradigm (Enhanced Reflexive Saccades)

Timing: 1000ms fixation, 200ms gap (blank), then target
Effect: Gap increases reflexive saccade errors in antisaccade
Purpose: Examine inhibitory control under stronger prepotent response

Mixed Block (Advanced)

Trials: Pro and anti randomly intermixed
Cue: Color/shape cue indicates pro vs. anti on each trial
Purpose: Maximize response conflict and test rapid task-switching

Participant Experience

Instructions: Learn to respond "Same side" or "Opposite side" depending on the trial label shown on screen (paradigm names are never exposed to participants)
Practice - Same Side: Each trial shows "Same side" label; respond with the arrow key toward the dot (10 trials)
Practice - Opposite Side: Each trial shows "Opposite side" label; respond with the arrow key toward the other side (10 trials with feedback)
Main Same-Side Block: 30 trials, respond to indicate direction
Break: Brief rest and reminder
Main Opposite-Side Block: 30 trials, respond toward the other side
Completion: See accuracy for each block

Response Methods

Keyboard (recommended):

Press Left Arrow Key (←) for left response (default -- configurable by researcher)
Press Right Arrow Key (→) for right response (default -- configurable by researcher)

Buttons (if button mode):

Click "Left" or "Right" button on screen

All keyboard bindings are configurable by the researcher in the study configuration. The keys listed above are the defaults.

Design Recommendations

General Guidelines

Block Order: Counterbalance pro-first vs. anti-first across participants
Trial Count: 30-40 trials per condition for stable error rates
Instructions: Emphasize speed AND accuracy (don't just respond quickly without controlling saccade)
Target Eccentricity: 8-12° typical; closer = harder to inhibit

Gap/Overlap Manipulation

Overlap: Target appears while fixation still visible (easier to inhibit)
Gap: 200ms blank before target (harder, more errors)
Express Saccades: Very short latency saccades in gap condition

Population-Specific Adaptations

Children (8+ years):

Extended practice (15-20 trials per condition)
Slower pacing
Gamification ("look at the spaceship" vs. "look at the empty space")
Expect higher error rates (15-30%)

Older Adults (65+):

Clear, high-contrast targets
Generous time limits
More practice trials
Expect moderately elevated errors (12-20%)

Clinical Populations:

Schizophrenia: Expect 40-50% antisaccade errors
ADHD: Elevated errors and RT variability
Parkinson's: Impaired antisaccades, normal prosaccades
Frontal damage: Severe antisaccade deficit

Common Issues and Solutions

Issue	Solution
High prosaccade errors (>5%)	Participants misunderstand task; add more practice
No antisaccade cost	Task too easy; reduce target eccentricity or add gap
Participants close eyes	Emphasize keeping eyes open throughout trial
Manual response doesn't match saccade	Emphasize honest reporting; ideally use eye-tracking
Ceiling effects (perfect antisaccade)	Use gap paradigm or mixed block to increase difficulty

References

Hallett, P. E. (1978). Primary and secondary saccades to goals defined by instructions. Vision Research, 18(10), 1279-1296.
Munoz, D. P., & Everling, S. (2004). Look away: The anti-saccade task and the voluntary control of eye movement. Nature Reviews Neuroscience, 5(3), 218-228.
Hutton, S. B., & Ettinger, U. (2006). The antisaccade task as a research tool in psychopathology: A critical review. Psychophysiology, 43(3), 302-313.
McDowell, J. E., Dyckman, K. A., Austin, B. P., & Clementz, B. A. (2008). Neurophysiology and neuroanatomy of reflexive and volitional saccades. Journal of Neurophysiology, 100(6), 3053-3062.

Overview​

Scientific Background​

Why Researchers Use This Task​

Current Implementation Status​

Configuration Parameters​

Display Options​

Behaviour Options​

Trial Spreadsheet​

Keyboard Shortcuts​

Data Output​

Markers​

Response Data​

Summary Artifact​

Example Research Configurations​

Standard Pro/Antisaccade​

Gap Paradigm (Enhanced Reflexive Saccades)​

Mixed Block (Advanced)​

Participant Experience​

Response Methods​

Design Recommendations​

General Guidelines​

Gap/Overlap Manipulation​

Population-Specific Adaptations​

Common Issues and Solutions​

References​

See Also​