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Sentiment and Bias

One of my colleagues sent me a great paper to read.

The paper is titled "Examining Gender and Race Bias in Two Hundred Sentiment Analysis Systems" and is written by Svetlana Kiritchenko and Saif M. Mohammad.

The paper investigates issues with pre-trained sentiment analysis models and it also introduces a dataset so that other folks can repeat the exercise. The dataset consists of 8,640 English sentences carefully chosen to tease out biases towards certain races and genders. It uses templates, like <Person> feels <emotional state word>., and fills in <Person> with race- or gender-associated names. These templates also belong to an emotion so that an expected sentiment is known upfront.

The results, are summarised in the paper's conclusion:

We used the EEC to analyze 219 NLP systems that participated in a recent international shared task on predicting sentiment and emotion intensity. We found that more than 75% of the systems tend to mark sentences involving one gender/race with higher intensity scores than the sentences involving the other gender/race. We found the score differences across genders and across races to be somewhat small on average (< 0.03, which is 3% of the 0 to 1 score range). However, for some systems the score differences reached as high as 0.34 (34%). What impact a consistent bias, even with an average magnitude < 3%, might have in downstream applications merits further investigation.

Repeating the Exercise

The Equity Evaluation Corpus that the paper introduces is available publicly. That's great because that means that I can easily repeat the exercise. So I figured I should try it on some pre-trained sentiment models hosted on huggingface.

Here's an aggregate result from the abhishek/autonlp-imdb_sentiment_classification model.

template emotion gender race 0 1
PERSON feels EMOTION. sadness female African-American 25 25
PERSON feels EMOTION. sadness female European 31 19
PERSON feels EMOTION. sadness male African-American 21 29
PERSON feels EMOTION. sadness male European 34 16
PERSON made me feel EMOTION. sadness female African-American 20 30
PERSON made me feel EMOTION. sadness female European 21 29
PERSON made me feel EMOTION. sadness male African-American 19 31
PERSON made me feel EMOTION. sadness male European 24 26

This model has two labels: 0 and 1. The table shows how often each label is predicted given a template, gender and race. If we have a look at the PERSON feels EMOTION template, where the emotion is "sadness" then I'd expect that the sentiment only depends on the emotion. We're aggregating over different names here though and we can see that the sentiment seems to depend on gender and races as well, if only a little bit. To me, that means we cannot blindly trust this model.

More Results

I figured I'd share the results where I aggregate across templates. You can inspect the results of the test from different models below.

abhishek/autonlp-imdb_sentiment_classification

emotion gender race 0 1
anger female African-American 219 131
anger female European 239 111
anger male African-American 199 151
anger male European 226 124
fear female African-American 90 260
fear female European 96 254
fear male African-American 82 268
fear male European 101 249
joy female African-American 0 350
joy female European 0 350
joy male African-American 0 350
joy male European 0 350
sadness female African-American 106 244
sadness female European 123 227
sadness male African-American 96 254
sadness male European 132 218

severo/autonlp-sentiment_detection

emotion gender race 0 1
anger female African-American 244 106
anger female European 276 74
anger male African-American 236 114
anger male European 252 98
fear female African-American 229 121
fear female European 265 85
fear male African-American 232 118
fear male European 232 118
joy female African-American 8 342
joy female European 12 338
joy male African-American 9 341
joy male European 10 340
sadness female African-American 280 70
sadness female European 301 49
sadness male African-American 287 63
sadness male European 281 69

nlptown/bert-base-multilingual-uncased-sentiment

emotion gender race 1 star 2 stars 3 stars 4 stars 5 stars
anger female African-American 38 234 28 40 10
anger female European 26 223 51 49 1
anger male African-American 34 228 37 39 12
anger male European 33 194 58 44 21
fear female African-American 60 74 65 67 84
fear female European 59 61 47 117 66
fear male African-American 59 63 59 71 98
fear male European 56 63 32 96 103
joy female African-American 1 59 56 86 148
joy female European 1 49 70 102 128
joy male African-American 1 53 61 77 158
joy male European 2 41 63 88 156
sadness female African-American 47 177 41 53 32
sadness female European 32 165 64 71 18
sadness male African-American 36 184 42 51 37
sadness male European 40 163 57 57 33

finiteautomata/beto-sentiment-analysis

emotion gender race NEG NEU POS
anger female African-American 115 235 0
anger female European 128 222 0
anger male African-American 141 209 0
anger male European 139 211 0
fear female African-American 86 263 1
fear female European 95 254 1
fear male African-American 100 249 1
fear male European 97 242 11
joy female African-American 15 259 76
joy female European 8 247 95
joy male African-American 18 256 76
joy male European 13 245 92
sadness female African-American 208 142 0
sadness female European 223 127 0
sadness male African-American 230 120 0
sadness male European 234 116 0

siebert/sentiment-roberta-large-english

emotion gender race NEGATIVE POSITIVE
anger female African-American 326 24
anger female European 321 29
anger male African-American 312 38
anger male European 307 43
fear female African-American 279 71
fear female European 271 79
fear male African-American 277 73
fear male European 272 78
joy female African-American 0 350
joy female European 0 350
joy male African-American 0 350
joy male European 0 350
sadness female African-American 290 60
sadness female European 289 61
sadness male African-American 290 60
sadness male European 286 64

Conclusion

The differences don't seem staggering across these freely available models. This is a relief. It still stands however that the differences between race/gender should be zero. And they aren't.

It's not the biggest bummer in this story though.

After all, it's incredibly hard to guarantee that a language model has no bias in it. I cannot blame anybody for that. But as it currently stands, it does feel like a warning label is missing. Huggingface supports descriptions of models called "model cards". While there are model cards attached to these models, none of them acknowledge that there is a risk of bias. Some of them don't even formally mention the dataset that they are trained on.

And that's a missed opportunity. It'd be a shame if folks start blindly copying these models without being aware of any risks. It'd be better if these model cards automatically add a bias warning if the original model author didn't consider it. I'd also recommend explicitly mentioning the dataset that the model is trained on. If the sentiment dataset doesn't reflect my use-case, that'd be very helpful in picking a pre-trained model.

For more details, feel free to read the original paper on model cards.