Does the Early Signal Generalise?
Ongoing research. This is an experimental result from active work, not a settled conclusion. The numbers are what we measured and the method is described so you can judge it, but the programme is still running and later experiments may revise what it means. More about this programme.
EXPLORATORY. Not a preregistered study. Local CPU, 15 training runs, no GPU, no cost.
Program v2 tier 3 follow-up to F2 and E3. Decisive computation: . Output: analysis/decode_probe_architectures.py. Reproduce with analysis/decode_probe_architectures.jsonpython analysis/decode_probe_architectures.py in about forty minutes on a throttled laptop CPU.
The question
F2 found the program's only leading indicator, in a GRU. E3 found that the expansion is a gated-recurrence phenomenon, present in the LSTM and absent in attention.
Those are different quantities. The expansion is about how a representation reorganises; the decode gap is about whether information arrives before it is used. There is no reason they must travel together, and it matters a great deal which way this falls: the indicator is the one result in this program with practical use, so its scope is the scope of anything useful that comes out of it.
Design. One task, dispatch-copy-wide-vocab, because it is the only cell in the E3 grid where all three architectures genuinely learn. The transformer solves plain delayed-copy almost instantly: that is the confound A1 was written about, and no lead can be measured against a model that arrives already knowing the answer. Learning rates are the ones E3 screened per cell on its excluded seed. Five seeds per arm, crossing measured at 40% accuracy.
Result: they travel together
| Architecture | Lead | Resolvable | Max probe-minus-model gap | Probe / model at end | Instrument check |
|---|---|---|---|---|---|
| gru | +23.4 [+18.8, +28.1] | 5 / 5 | +0.0721 | 0.6216 / 0.6141 | 5 / 5 |
| lstm | +14.4 [+11.0, +17.9] | 5 / 5 | +0.0575 | 0.7156 / 0.7095 | 5 / 5 |
| transformer | +1.3 [+0.6, +2.0] | 0 / 5 | +0.0711 | 0.8300 / 0.8236 | 5 / 5 |
The lead appears where the expansion appears, and not in attention. Both are gated-recurrence properties. That is the second of the three outcomes this pilot was written to distinguish.
Two things that make the transformer's null trustworthy
The instrument check passes in all three arms, including the transformer. An optimally fitted linear readout matches the trained head at convergence in 5 of 5 transformer runs (0.8300 against 0.8236). This is exactly the guard F2's own correction installed, and here it is doing its job: the transformer's null is not the under-powered-probe failure that made F2's first version report the opposite of the truth. The probe works. It simply finds no lead.
The transformer's gap is real but not temporal. Its largest probe-minus-model gap (+0.0711) is comparable to the GRU's (+0.0721). The probe is consistently a little better than the trained head. What it is not is earlier: the two curves rise together, so the gap is a constant offset rather than a lead. That distinction is the whole point of measuring a crossing time rather than a gap size, and a pilot that reported only the gap would have concluded the opposite.
The GRU result replicates on a new task
F2 measured +23.5 steps [+22.1, +24.9] on delayed-copy. This measures +23.4 [+18.8, +28.1] on dispatch-copy-wide-vocab: a different task, a different vocabulary size, a different learning rate, and unseen seeds. That is an independent replication of the program's most important positive result, and it was not the question this pilot was asked.
What this changes
- F2's scope is now known, and it is the same as the expansion's: gated recurrence. Anything built on the leading indicator inherits that limit, and the honest framing of the program's one useful finding is "in gated recurrent models" rather than "in models".
- The two findings are one story, not two. Whatever gating does at the moment of learning produces both the representational expansion and the gap between what the state carries and what the head reads. That strengthens the case for making gating the object of study, which E3 already recommended.
- The transformer remains the interesting negative. It learns the task, takes the longest of any architecture to do it, shows no expansion, and shows no lead, while a calibrated probe confirms the information is slightly more decodable than the head manages throughout. Attention appears to acquire and use information at the same time.
Limits
- One task, five seeds per arm, one width, one optimizer. This is a scope check on F2, not a second independent confirmation of it.
- The crossing is measured at 40% rather than F2's 50%, because the arms plateau between 0.61 and 0.83 on this task and 50% sits too close to the transformer's own curve to time reliably. F2 established that its lead is robust across thresholds from 20% to 90%; that robustness was not re-established here.
- The transformer is one configuration (1 layer, 4 heads). "Attention does not show this" is a claim about that configuration, not about attention at scale.