Cowan Working Memory Capacity
Calculate the change-detection estimate K = setSize × (hitRate − falseAlarmRate), with rates as fractions. Preserve negative estimates without clipping; the caller supplies task-appropriate rates.
Description
Change-detection capacity estimates relate set size to hit rate corrected for false alarms.
Change-detection capacity estimates relate set size to hit rate corrected for false alarms. The estimate describes a task-specific model, not a general clinical memory score.1
Calculate the change-detection estimate K = setSize × (hitRate − falseAlarmRate), with rates as fractions. Preserve negative estimates without clipping; the caller supplies task-appropriate rates.
When to use Cowan Working Memory Capacity
Use this tool to calculate the change-detection estimate K = setSize × (hitRate − falseAlarmRate), with rates as fractions. Preserve negative estimates without clipping; the caller supplies task-appropriate rates.
Prepare the task-specific rates, comparable response-time means, identified spike train, processed ERP or estimated spectra requested. Confirm units, preprocessing, sample pairing and caller-fitted model coefficients.
How to use Cowan Working Memory Capacity and understand its results
- Prepare the task-specific rates, comparable response-time means, identified spike train, processed ERP or estimated spectra requested. Confirm units, preprocessing, sample pairing and caller-fitted model coefficients.
- Enter setSize, hitRate, falseAlarmRate using the field table and calculation rules, then run the tool.
- Read capacityItems. The explanation below defines the units, signs, ordering and any flags or placeholder values.
- If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.
| Input field | Meaning | Value type; see rules below | Requirement |
|---|---|---|---|
| setSize | Number of items in the memory set. | integer; minimum: 1 | Required |
| hitRate | Fraction of change trials correctly detected. | number; minimum: 0; maximum: 1 | Required |
| falseAlarmRate | Fraction of no-change trials incorrectly called change. | number; minimum: 0; maximum: 1 | Required |
Enter integer set size of at least one and hit/false-alarm fractions in 0–1. Multiply their signed difference by set size and return capacityItems without clipping negative values.
K=setSize×(hitRate−falseAlarmRate) Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| capacityItems | Signed Cowan K estimate. (item) | number |
{
"input": {
"setSize": 4,
"hitRate": 0.9,
"falseAlarmRate": 0.15
},
"output": {
"capacityItems": 3
}
}Limitations and assumptions
Task design, rate estimation, uncertainty and participant calibration are supplied responsibilities. The result can be negative and does not diagnose impairment.
Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.
Alternative or Complementary methods
Use Hick Choice Reaction Time: Evaluate the equally likely choice form RT = a + b × log2(n), using caller-fitted coefficients in milliseconds. Predictions must be nonnegative; this is a model evaluation without participant calibration. For a complementary task, use Stroop Interference: Calculate the signed stroop interference as mean incongruent response time minus mean congruent response time in milliseconds, using caller-prepared comparable correct-trial means.
References
-
Cowan Working Memory Capacity — tool.io
Similar or alternative tools
- Hick Choice Reaction Time
Evaluate the equally likely choice form RT = a + b × log2(n), using caller-fitted coefficients in milliseconds. Predictions must be nonnegative; this is a model evaluation without participant calibration.
- Stroop Interference
Calculate the signed stroop interference as mean incongruent response time minus mean congruent response time in milliseconds, using caller-prepared comparable correct-trial means.