bert-finetuned-imdb — Sentiment Classification (Positive / Negative)

Overview (what this model is)

bert-finetuned-imdb is a sentiment classification model that takes an English text (typically review-like text) and predicts whether the overall sentiment is:

• Positive (the author is favorable / satisfied / approving), or
• Negative (the author is unfavorable / dissatisfied / critical).

It is built by fine-tuning the transformer model BERT (bert-base-uncased) for binary text classification.

You can think of this model as a rule-free automatic tagger that reads a sentence or paragraph and outputs a sentiment label plus a confidence score.

---

What you can do with it (practical uses)

This model is useful when you have a lot of text feedback and you want a quick, consistent way to label it.

Common use cases:

1. Review analysis

   • Movie reviews
   • Product reviews
   • App store reviews

2. Customer feedback triage

   • Mark feedback as “positive” vs “negative”
   • Route negative feedback for faster response
   • Track sentiment trends over time

3. Survey responses / open-text fields

   • Convert free-text answers into measurable sentiment

4. Dashboards & analytics

   • Compute % positive / negative by week, campaign, product, etc.
   • Use sentiment as one feature in a bigger reporting system

---

What the output means

When you run the model, you typically receive something like:

[
  {
    "label": "POSITIVE",
    "score": 0.992
  }
]

---

```python
from transformers import pipeline

clf = pipeline("text-classification", model="Anant1213/bert-finetuned-imdb")

print(clf("This movie was fantastic, I loved it!"))
print(clf("Worst film ever. Completely boring."))

---

How and why it works (simple explanation)

What is BERT?

BERT is a neural model trained to understand language patterns and context (how words relate to each other in a sentence).

What is fine-tuning?

Fine-tuning teaches BERT one specific job:
given a review → output positive or negative.

Why this is usually better than simple rules

Keyword rules fail on phrases like:

• “not good”
• “good but disappointing”
• “hardly impressive”

BERT-based models consider context, so they usually handle these better.

---

Differences between sentiment approaches (with examples)

People often ask: “Why use this model instead of a simpler method or a bigger model?”
Below is a practical comparison.

The 4 common options

1. Keyword / rule-based

   • Example rule: if text contains “good” → positive
   • Fast, but often wrong on negation/mixed opinions.

2. Traditional ML (Logistic Regression / SVM + TF-IDF)

   • Learns from word counts and common phrases.
   • Better than rules, but still limited at understanding context.

3. BERT fine-tuned classifier (this model)

   • Understands context better.
   • Usually stronger on negation and phrasing.

4. Large LLMs (chat models) for sentiment

   • Can handle nuance and explanations.
   • But heavier/expensive, slower, and sometimes inconsistent without strict prompting.

---

Side-by-side examples (what typically happens)

Note: The exact outputs differ by implementation. The point here is the behavioral difference.

Example 1: Negation

Text: “The movie was not good.”

• Keyword rules: ❌ often Positive (sees “good”)
• TF-IDF + Logistic Regression: ✅ usually Negative
• This BERT model: ✅ Negative (handles “not good” well)
• Large LLM: ✅ Negative (and can explain why)

Example 2: Mixed sentiment

Text: “Great acting, but the story was terrible.”

• Keyword rules: ❌ often Positive (sees “great”)
• TF-IDF + Logistic Regression: ⚠️ depends; can flip either way
• This BERT model: ✅ usually picks Negative (because “terrible” dominates overall sentiment)
• Large LLM: ✅ can say Mixed, but if forced to choose binary may pick Negative

Important: This model is binary, so it must choose one label even when the text is mixed.

Example 3: Subtle negative phrasing

Text: “I expected more.”

• Keyword rules: ⚠️ often Neutral/unknown
• TF-IDF + Logistic Regression: ⚠️ depends (may miss it)
• This BERT model: ✅ often Negative (common review pattern)
• Large LLM: ✅ Negative with explanation

Example 4: Sarcasm (hard case)

Text: “Amazing… I fell asleep in 10 minutes.”

• Keyword rules: ❌ Positive (sees “Amazing”)
• TF-IDF + Logistic Regression: ⚠️ inconsistent
• This BERT model: ⚠️ may still fail sometimes (sarcasm is genuinely hard)
• Large LLM: ✅ more likely to catch sarcasm, but not guaranteed

Takeaway: If sarcasm is common in your data, test carefully.

---

When to choose which approach (simple guide)

• Choose keyword rules if you need something quick, tiny, and you accept lower accuracy.
• Choose traditional ML (TF-IDF + LR) if you need fast inference and decent baseline results.
• Choose this BERT model if you want a strong balance of:
  • accuracy
  • speed
  • consistent binary outputs
• Choose large LLMs if you need:
  • explanations
  • “mixed/neutral” labels
  • deeper nuance
    (but you pay in cost, speed, and potential variability)

---

Limitations (important)

• Only two labels (positive/negative). No neutral or mixed label.
• Sarcasm and humor can confuse it.
• Very short text is often ambiguous (“ok”, “fine”).
• Works best on English review-style text similar to IMDb.

Practical rule: if score < 0.60, treat it as uncertain and review manually.

---

Training and evaluation data

Intended fine-tuning dataset: IMDb movie reviews (binary sentiment).
Input: review text → Output: positive/negative label.

If you trained on a different dataset, update this section so the card remains accurate.

---

Training procedure (transparency)

Base model: bert-base-uncased

Hyperparameters:

• learning_rate: 2e-05
• train_batch_size: 8
• eval_batch_size: 8
• num_epochs: 11
• seed: 42
• optimizer: AdamW (torch fused)
• lr_scheduler_type: linear

Evaluation metric available:

• Eval Loss: 0.0014 (lower is generally better)

---

Ethical considerations

• May reflect biases present in training data.
• Not recommended as the sole decision-maker for high-stakes decisions.
• Always evaluate on your own domain text before production use.

---

Framework versions

• Transformers: 4.57.3
• PyTorch: 2.9.0+cu126
• Datasets: 4.4.2
• Tokenizers: 0.22.1

---

License

Apache-2.0

---

Citation

BERT paper (base architecture):

Devlin, J., Chang, M.-W., Lee, K., & Toutanova, K. (2018).
BERT: Pre-training of Deep Bidirectional Transformers for Language Understanding