# ConductScience NOR Discrimination Index Calculator: method and validation record

This record fixes the calculation behind the free NOR Discrimination Index Calculator at https://conductscience.com/tools/novel-object-recognition-calculator, and the worked examples that check it.

## What the tool computes

From the time each animal spends exploring the novel and the familiar object in the test phase of a novel object recognition task:

- the discrimination index DI = (N − F) / (N + F);
- the preference index PI = N / (N + F);
- group means, SDs and SEMs of both indices.

Times are scored live with two keys or entered as totals. An animal that explored neither object has no index.

## Files

| File | Contents |
| --- | --- |
| `METHODS.md` | Formulas, conventions, references, and changes from the page before this record |
| `cases.json`, `cases.csv` | The worked examples: inputs, expected outputs and where each expected answer comes from |
| `validation-report.json` | The engine's output for every case, pass or fail, and the SHA-256 of each engine file |
| `engine/` | The calculation source files the report fingerprints (when included) |
| `data_dictionary.csv` | Columns of `cases.csv` |
| `CITATION.cff`, `LICENSE`, `MANIFEST.json` | Citation metadata, licence, and byte count and SHA-256 of every file |

## How to cite

ConductScience. ConductScience NOR Discrimination Index Calculator [software]. 2026. https://doi.org/10.55157/csd.tool.nor.2026.001

In a methods section: "Discrimination indices, DI = (N − F) / (N + F) (Ennaceur and Delacour, 1988), were calculated with the ConductScience NOR Discrimination Index Calculator (https://doi.org/10.55157/csd.tool.nor.2026.001)."