Visual Symbol Search Task

Version: v1 (current)

A processing speed task measuring the ability to quickly scan and compare visual symbols.

Overview

The Visual Symbol Search task assesses perceptual speed and visual attention by presenting a target symbol alongside an array of symbols. Participants must quickly determine whether the target appears in the array. Unlike visual search tasks that study attention mechanisms, symbol search emphasizes processing speed, measuring how fast you can scan and compare visual information.

This task is widely used in neuropsychological assessment batteries (e.g., WAIS, WISC) as a measure of processing speed, visual scanning, and sustained attention. Performance correlates with working memory, learning disabilities, and general cognitive efficiency.

Scientific Background

Classic Findings:

Processing Speed: Healthy adults complete 20-30 items per minute
Age Trajectory: Speed increases through childhood, peaks in young adulthood, declines with aging
Individual Differences: Correlates with IQ, working memory, and academic achievement
Practice Effects: Modest improvement with repeated administration

Key Mechanisms:

Perceptual Speed: Rapid rate of visual information processing
Visual Scanning: Systematic or random search through array
Decision Speed: Quick match/no-match judgment

Seminal Papers:

Wechsler (1997): WAIS-III and processing speed index
Salthouse (1996): The processing-speed theory of adult age differences in cognition

Why Researchers Use This Task

Neuropsychological Assessment: Standard measure of processing speed
Educational Psychology: Identify learning disabilities and processing deficits
Aging Research: Sensitive to age-related cognitive slowing
Clinical Screening: Assess attention and processing in ADHD, brain injury
Research on Cognitive Efficiency: Correlate with other cognitive abilities

Where to Configure

Study Form → Tasks → Visual Symbol Search → Configure.

Configuration Parameters

Parameter	Type	Default	Description
Array Size	number	5	Number of symbols in the search array
Time Limit (ms)	number	120000	Total time for the task (default: 2 minutes)
Trials	number	40	Number of items to complete
Target Present Probability	number	0.5	Proportion of trials where the target is present

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
Yes key	key	Y	Key for "yes" (match found) response
Yes action label	text	"Yes"	Label shown in the keyboard hint
No key	key	N	Key for "no" (no match) response
No action label	text	"No"	Label shown in the keyboard hint

Participant Flow

The participant sees a target symbol at the top of the screen and a row of symbols below.
The participant decides as quickly as possible whether the target symbol appears in the row.
The participant presses Y for "Yes" or N for "No" (or clicks the corresponding buttons) to respond. (Default keys -- configurable by researcher.)
The next trial appears immediately. Trials continue until all items are completed or the time limit expires.
Accuracy and response time are recorded for each trial.

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

Data Output

Markers and Responses

The task records high-resolution timestamps in two separate collections:

Markers (stimulus_shown):

{
  "type": "stimulus_shown",
  "ts": "2024-01-01T00:00:01.000Z",
  "hr": 1234.56,
  "data": {
    "trial_index": 1,
    "stimulus_id": "visual_symbol_search_0_1",
    "target_symbols": ["triangle", "circle"],
    "search_symbols": ["square", "circle", "diamond", "star", "pentagon"],
    "contains_target": true,
    "block": "main",
    "difficulty": 2,
    "is_practice": false
  }
}

Response Data:

{
  "trial_index": 1,
  "stimulus_id": "visual_symbol_search_0_1",
  "source": "keyboard",
  "raw_key": "y",
  "target_symbols": ["triangle", "circle"],
  "search_symbols": ["square", "circle", "diamond", "star", "pentagon"],
  "contains_target": true,
  "response_value": true,
  "response_correct": true,
  "is_practice": false,
  "block": "main",
  "difficulty": 2,
  "latency_ms": 1250
}

Summary Artifact

A JSON file (visual_symbol_search_summary_<taskIndex>.json) with signal detection metrics:

{
  "task_kind": "visual_symbol_search",
  "task_index": 0,
  "total_trials": 40,
  "overall": {
    "total": 40,
    "valid_responses": 38,
    "correct": 34,
    "accuracy": 0.89,
    "mean_rt_ms": 1250,
    "mean_correct_rt_ms": 1180,
    "timeouts": 2,
    "hits": 17,
    "misses": 2,
    "false_alarms": 2,
    "correct_rejections": 17,
    "sensitivity": 0.89,
    "specificity": 0.89
  },
  "by_block": { /* block statistics if blocks defined */ },
  "by_difficulty": { /* difficulty statistics if defined */ },
  "trials": [ /* per-trial data */ ]
}

Key metrics:

sensitivity: Hits / (Hits + Misses) -- ability to detect present targets
specificity: Correct Rejections / (Correct Rejections + False Alarms) -- ability to reject absent targets
hits: Target present + "Yes" response
false_alarms: Target absent + "Yes" response

Design Recommendations

Array Size: 5 symbols is standard for adult populations. Reduce to 3-4 for children or clinical populations.
Time Limit: Two minutes is standard. Ensure the limit is long enough for most participants to attempt all items.
Trial Count: 40 items is typical for research; 60 items provides more reliable estimates.
Target Probability: 50% present/absent is standard. Varying this can increase task difficulty.
Practice Trials: Include practice trials with feedback so participants understand the task before timed testing begins.
Symbol Sets: Use abstract symbols (geometric shapes) to minimize cultural or linguistic bias.

Common Issues and Solutions

Issue	Solution
Participants respond too slowly	Emphasize speed in instructions; ensure practice trials are completed
Accuracy is very low	Reduce array size; add more practice trials; check that symbols are visually distinct
Time limit expires before all trials completed	Increase time limit or reduce trial count; this is expected for some clinical populations
Floor or ceiling effects	Adjust array size or trial count to match your population

References

Wechsler, D. (1997). WAIS-III: Wechsler Adult Intelligence Scale (3rd ed.). The Psychological Corporation.
Salthouse, T. A. (1996). The processing-speed theory of adult age differences in cognition. Psychological Review, 103(3), 403-428.

Overview​

Scientific Background​

Why Researchers Use This Task​

Where to Configure​

Configuration Parameters​

Keyboard Shortcuts​

Participant Flow​

Data Output​

Markers and Responses​

Summary Artifact​

Design Recommendations​

Common Issues and Solutions​

References​

See Also​