Ifan Johnston

Ifan Johnston

Understanding form and the Octopus test

I recently listened to an episode of the Gradient Dissent (the Weights & Biases podcast) with Emily Bender in which they discussed Language Models (LM) and the dangers arising from making increasingly larger ones. The discussion was primarily centered around the paper On the Dangers of Stochastic Parrots: Can Language Models Be Too Big? 🦜. They also discuss some ideas from Climbing towards NLU: On Meaning, Form, and Understanding in the Age of Data (E. Bender & A. Koller, 2020). Here I wanted to present a few of the ideas discussed in the podcast episode and the referenced papers.

Meaning, form and understanding

My favourite quote from the Bender & Koller1 paper is the following,

Meaning cannot be learned from form alone - E. Bender, A. Koller (2020)

Everytime a new larger language model is released, there appears new articles claiming that the model 'understands' language. The term 'understanding' is quite the loaded term, and needs to be carefully examined before claiming that a machine learning model possesses it. Because language models are trained on text (form), it is not possible for the language model to learn meaning from the data in the same way as a person would learn from it. It can learn to associate inputs to outputs, and learn to pick out clusters of words that are associated with each other - but that is not the same as understanding the meaning.

Getting an accurate and consistent definition of 'meaning' and 'knowledge' is surprisingly difficult. Here are some useful definitions from Bender & Koller1

Form - Any observable realization of language. For example, marks/words on a page, pixels in an image, movements of hands in sign language or the dashes and dots of Morse code.

Communicative Intent is grounded in the real world that the speaker and listener inhabit together.

There are many types of communicative intents: they may be to convey some information to the other person; or to ask them to do something; or simply to socialize.

Conventional Meaning of an expression is what is constant across all of it's possible context of use. Conventional meaning is an abstract object that represents the communicative potential of a form, given the linguistic system it is drawn from.

Meaning is the relation between form and communicative intent

So meaning is made up out of two things, an expression of language (form) and the communicative intent which may be independent of the form.

Then to understand something is the process of retrieving the communicative intent given the form.

So in a conversation between two people, the speaker has a certain communicative intent i, and chooses an expression e with a standing (conventional) meaning s which is fit to express i in the current communicative situation. Upon hearing e, the listener then reconstructs s and uses their own knowledge of the communicative situation and their hypotheses about the speaker’s state of mind and intention in an attempt to deduce i.

It is often impossible to say something that doesn't require knowledge/understanding about the world. Let's look at an example,

  • Person A and B are sat on opposite sides of a table. There is a clock on the wall behind person A.
  • "The clock says that it is almost 10pm", says A.
  • Person A and B both get up and go to the next room to watch TV

Person A had the communicative intent of wanting to say what the time was, because A knew that their favourite TV show starts at 22.00, so they had better go to the TV room. Person A then chose the expression (the form) "the clock says that it is almost 10pm" which they feel has the conventional meaning of telling the time and is enough to express their communicative intent.

Upon hearing this expression, person B then begins the task of reconstructing the conventional meaning of the form, and then use their knowledge of the world2 to deduce that person A's communicative intent was that they should go to the TV room because it is almost 22.003.

Given only the expression that A used, a language model would not have much hope to really understand what the intent was.

It's also interesting to think about how we know that the 'clock' is almost certainly not a thing that can speak, nor do we expect it 'say' anything else other than the correct time (let's assume that it is a magical clock that is never wrong). How do we know these things? We just know that the idea of a talking clock is nonsense, and only happens in sci-fi stories.

The Octopus test

An interesting thought experiment that Bender and Koller discuss in their paper is a test they call the octopus test, which illustrates the difficulty in learning from form alone. Imagine that person A and B are independently stranded on two deserted islands, but they can communicate with each other via an underwater cable and often send text messages in english to each other.

Without either person A or B's knowledge another entity O (a very clever octopus) who cannot speak english but has a very advanced knowledge of statistics and pattern matching.

After some very long time, O decides to cut the wire so that they can speak directly to each person. The question is, could O have learned enough from the form (the text messages) so that neither person knows that anything has changed?

The answer depends on the nature of the task that O is given. If person A and B have been using the text messages for small talk (i.e, a communicative intent of 'socialising'), then O would likely have learned enough from the form to be able to continue this small talk. But this is not the same as O understanding what A is talking about, it just means that A is doing the mental work of attributing meaning to the responses of O.

If person A suddenly needs advice about how to construct a weapon to defend itself from a bear, then there is no chance that O could give a helpful response unless it has some external knowledge about the theory of crafting weapons from coconuts and sticks.

Stochastic Parrots

Another important aspect of language models that needs to be understood is that the data these models are trained on can often harbour significant biases. For example, the Switch-C4 transformer model was trained Colossal Clean Common Crawl dataset (which is about ~750GB of data), which is text taken from the internet. To start with, think about what kind of people are represented in this sort of data. Internet data over-represents younger users and those from developed countries.

As we have already discussed, understanding language is a process of pairing form with meaning, and since these large internet datasets only contain form, language models learning from such datasets cannot really gain understanding.

Since large language models don't really learn to understand meaning from these large datasets, in order to understand what they actually do learn, it is important to understand what is contained in the training data. Stereotypcial associations and negative sentiments towards specific groups can often be found in internet datasets - so these views usually find their way into large LMs. As their usage increases, these biases may end up being reinforced - especially if decisions start being made upon the predictions of these models.

The stochastic parrot paper suggests that we need to be mindful about how we currate and create these datasets in future.

  1. Climbing towards NLU: On Meaning, Form, and Understanding in the Age of Data (Bender & Koller, 2020)
  2. Or: their knowledge of the mental state of the other person in the conversation, along with the TV schedule
  3. why didn't they just say "the time is now 21.56, we should move to the TV room because our favourite TV show is starting 4 minutes"??
  4. Switch Transformers: Scaling to Trillion Parameter Models with Simple and Efficient Sparsity (Fedus, Zoph & Shazeer, 2021)