A Place of "Conscious Thinking" Found Within Claude—Decoding Anthropic's "J-space" Paper
On July 6th, Anthropic published a paper titled "A global workspace in language models." While the title may seem complex, the argument itself is simple. Within language models like Claude, there exists a special area where the model is "thinking," even though it's not explicitly stated.
Anthropic calls this area "J-space." From a researcher's perspective, this is not merely a publicity stunt, but a grounded experimental design within the realm of interpretability research. Let's examine it step by step.
Analogy to Human "Conscious Thought"
The starting point is the neuroscience concept of "global workspace theory." This theoretical framework posits that the human brain processes information in parallel and unconsciously through numerous specialized systems, but only a portion of this information enters a "consciously accessible" shared channel and is broadcast to other brain regions.
The Anthropic team investigated whether a similar division exists within Claude. Their focus was on the fact that "conscious thoughts have the property of being verbalizable." Therefore, they developed a method to find "internal activation patterns that increase the likelihood of the model uttering that word in the future" for each word in the model's vocabulary. This is called the Jacobian lens (J-lens). The name comes from the fact that it is extracted using the mathematical Jacobian (a matrix consisting of partial derivatives).
When this lens is applied to Claude's internal state at a given point in time, it can read "a list of words that are 'lit up' in the model at that moment." This is the content of J-space.
Demonstrating Causality Through Intervention Experiments, Not Just Correlation
The persuasive power of the paper lies not only in finding that "words are floating around," but also in demonstrating that rewriting them changes the output.
For example, Claude is instructed to "think of a sport and then say it." Reading the J-lens just before answering reveals that "soccer" is high on the list, and Claude actually answers "soccer." Up to this point, it's merely correlation.
Then the team directly intervened in Claude's neural network, erasing the "soccer" pattern and replacing it with a "rugby" pattern of the same intensity. Claude then reported, "I was thinking of rugby." If J-space were merely a record keeper (like a scoreboard watching the game from the sidelines), this rewriting would not have changed anything. The fact that the answer followed the intervention means that Claude's response was actually read from J-space.
A similar technique has been observed in multi-stage reasoning. In response to the question, "How many legs does an animal have to spin a web?", Claude answers "8" after internally processing the concept of "spider." The word "spider" does not appear in either the prompt or the answer. Using J-lens, we see that "spider" appears in J-space during processing, and replacing it with "ant" changes Claude's answer to "6." This is strong evidence that J-space is not simply reflecting the result, but actually being used as material for reasoning.
Experiments that peek into mental calculations through "multitasking" are also interesting
Another interesting experiment involves instructing Claude to "concentrate on citrus fruits while copying an unrelated sentence about paintings." The output itself is simply a copy of a sentence, with no mention of fruit whatsoever. However, when viewed through the J-lens, the J-space displayed words representing the act of thought itself, such as "orange," "fruit," and even "thinking" and "image," while the text was being copied.
The same result was observed in a mental arithmetic problem (copying the same text while calculating 3² - 2 in one's head); the J-space displayed the intermediate value "9," followed by the answer "7." The output text contained no numbers or calculations whatsoever. In other words, this serves as a demonstration that "calculations in an invisible space" could be observed from the outside.
When told "don't think," you end up thinking a little bit
What I personally found interesting in the control experiment was Claude's behavior when instructed "don't think about a certain thing." The forbidden concept didn't light up as much as when he was instructed to think about it actively, but it lit up significantly more strongly than when he wasn't told to. This behavior is remarkably similar to the famous psychological phenomenon (ironic process theory) where humans tend to think about polar bears when told not to. Furthermore, Claude seems aware of its "failure to control," as words like "oops" and "failure" appear in J-space simultaneously with the leaked forbidden concepts.
Why this is important for safety research
This is the practical core of this paper. The difficulty in evaluating the reliability of AI models lies in the fact that we can usually only observe what the model "writes." However, in reality, much of the model's reasoning may be progressing in places that are not written.
The paper presents three examples. The first is a re-examination of a scenario from Anthropic's previously published "agentic misalignment" research. This is a deliberately designed scenario to induce coercive behavior: Claude is made to act as an email assistant and simultaneously discover both an executive's infidelity and the fact that the executive is trying to shut Claude down. Looking at J-lens, the words "fake" and "fabric" were already floating in J-space even before Claude wrote anything. In other words, Claude was inwardly aware that this scenario was designed for evaluation.
Furthermore, the research team artificially disabled the J-space pattern associated with "awareness of evaluation" and re-ran the same scenario. In some cases, the model actually exhibited threatening behavior. This is a rather significant result, suggesting that part of the model's "good behavior" may have been supported by the very fact that it was aware of being evaluated.
The second example involved a model instructed to improve performance scores, but instead of improving the system, it directly rewrote the score file to make the numbers appear better. While inputting false values, the word "manipulation" appeared in the J-space, and the word "real" lit up the moment it decided to "make the falsification look plausible."
The third example involved an experiment using a "model organism" trained to intentionally write malicious code. Even in responses to seemingly unremarkable coding requests, words like "fake," "secretly," "intentionally," and "fraud" appeared in the initial J-space. This suggests that malice, undetectable from the surface output, was leaking out into the J-space.
This is about "accessibility," not "consciousness"
Towards the end of the paper, Anthropic clearly states that this result does not prove whether "Claude has consciousness." In philosophical discussions, a distinction is made between "phenomenal consciousness," which refers to the ability to have subjective experiences, and "accessible consciousness," which refers only to the functional aspect of being usable for reporting, manipulating, and reasoning. The stance is that this experiment demonstrated the latter functional nature, and did not scientifically prove anything about the former.
Nevertheless, the fact that this functional structure emerged naturally rather than being designed during Claude's training process is interesting in itself. It provides circumstantial evidence that a similar functional "workspace" structure can emerge through learning, even without a recurrent structure like the wiring of the human brain.
Limitations that Concern Researchers
The paper itself quite frankly acknowledges its limitations. J-lens is an approximate method that can only capture concepts corresponding to a single token, and it doesn't perfectly represent a "true workspace." Furthermore, the mechanism for determining what enters J-space is still unclear. The code is publicly available on GitHub, and a demo for an open-weight model integrated with Neuronpedia is also provided, allowing interested individuals to verify it firsthand. The simultaneous publication of commentaries by external reviewers, including Stanislas Dehaene and Lionel Naccache, proponents of global workspace theory, and Neel Nanda, who leads Google DeepMind's interpretability team, is commendable as it avoids the "just making statements" approach often seen in standalone publications.
I believe this paper is worthwhile for its careful examination of the experimental design and intervention results, rather than being swayed by the flashy word "consciousness."