The Cognitive Divergence: AI Context Windows, Human Attention Decline, and the Delegation Feedback Loop
Organizations: Machine Human Intelligence Lab · Machine Human Intelligence Lab (MHIL)
Abstract
This paper documents and theorises a self-reinforcing dynamic between two measurable trends: the exponential expansion of large language model (LLM) context windows and the secular contraction of human sustained-attention capacity. We term the resulting asymmetry the Cognitive Divergence. AI context windows have grown from 512 tokens in 2017 to 2,000,000 tokens by 2026 (factor ~3,906; fitted lambda = 0.59/yr; doubling time ~14 months). Over the same period, human Effective Context Span (ECS) -- a token-equivalent measure derived from validated reading-rate meta-analysis (Brysbaert, 2019) and an empirically motivated Comprehension Scaling Factor -- has declined from approximately 16,000 tokens (2004 baseline) to an estimated 1,800 tokens (2026, extrapolated from longitudinal behavioural data ending 2020 (Mark, 2023); see Section 9 for uncertainty discussion). The AI-to-human ratio grew from near parity at the ChatGPT launch (November 2022) to 556--1,111x raw and 56--111x quality-adjusted, after accounting for retrieval degradation (Liu et al., 2024; Chroma, 2025). Beyond documenting this divergence, the paper introduces the Delegation Feedback Loop hypothesis: as AI capability grows, the cognitive threshold at which humans delegate to AI falls, extending to tasks of negligible demand; the resulting reduction in cognitive practice may further attenuate the capacities already documented as declining (Gerlich, 2025; Kim et al., 2026; Kosmyna et al., 2025). Neither trend reverses spontaneously. The paper characterises the divergence statistically, reviews neurobiological mechanisms across eight peer-reviewed neuroimaging studies, presents empirical evidence bearing on the delegation threshold, and proposes a research agenda centred on a validated ECS psychometric instrument and longitudinal study of AI-mediated cognitive change.
Figures & tables
| Parameter | Value | Source |
|---|---|---|
| Mean adult reading rate | 238 wpm (range 175–300) | Brysbaert (2019) ; Rayner et al. (2016) |
| Tokens per English word | 1.33 | OpenAI cl100k_base ( OpenAI, 2023b ) |
| Derived reading rate ( ) | 5.28 tokens/s | Computed: |
| Mark (2004) episode duration | 150 s | Mark (2023) |
| Mark (2016–20) episode duration | 47 s (median 40 s) | Mark et al. (2016) ; Mark (2023) |
| Session reading duration , 2004 | 1,515 s ( 25 min) | Estimated from Mark; Section 3.3 |
| Year | Leading Model | AI Context | Human ECS | Ratio |
|---|---|---|---|---|
| 2017 | Transformer ( Vaswani et al., 2017 ) | 512 | 13,500 | 0.04 |
| 2018 | GPT-1 ( Radford et al., 2018 ) | 512 | 12,000 | 0.04 |
| 2019 | GPT-2 ( Radford et al., 2019 ) | 1,024 | 10,500 | 0.10 |
| 2020 | GPT-3 ( Brown et al., 2020 ) | 2,048 | 9,000 | 0.22 |
| 2021 | Codex ( Chen et al., 2021 ) | 4,096 | 7,500 | 0.55 |
| Nov 2022 | ChatGPT ( OpenAI, 2022 ) | 4,096–8,192 | 6,000 | 0.7–1.3 |
| Scenario | CSF | CSF | CSF | ECS | ECS | Raw | QA |
|---|---|---|---|---|---|---|---|
| 2004 | 2022 | 2026 | 2004 | 2026 | Ratio | Ratio | |
| Conservative ( ) | 1.4 | 1.05 | 0.84 | 11,100 | 1,260 | 1,587 | 119 |
| Baseline (paper) | 2.0 | 1.5 | 1.2 | 16,000 | 1,800 | 1,111 | 83 |
| Generous ( ) | 2.6 | 1.95 | 1.56 | 20,800 | 2,340 | 855 | 64 |
| Maximum plausible | 2.8 | 2.1 | 1.68 | 22,400 | 2,520 | 794 | 60 |
| Flat CSF (no decline) | 2.0 | 2.0 | 2.0 | 16,000 | 3,000 | 667 | 50 |
| Study | Modality | Sample | Key Finding |
|---|---|---|---|
| Fernandes et al. (2025) | fMRI/EEG | Amygdala, vmPFC, ventral striatum activation; overlaps with SUD patterns | |
| Westbrook et al. (2021) | PET | Putamen dopamine synthesis (+) correlated with social app use intensity | |
| Aitken et al. (2025) | fNIRS | dlPFC/vlPFC activation decreased post-social media; mPFC increased | |
| Montag and Becker (2023) | MRI (rev.) | Various | Reduced frontopolar cortex engagement in high-use cohorts; ACC changes |
| He et al. (2017) | MRI | Reduced grey matter volume in amygdala bilaterally; parallels SUD structural findings | |
| Satani et al. (2025) | EEG | Gamma +62%; Beta ; persistent Alpha suppression post-use |
Appendix figures & tables1 asset
Supplementary material from the paper’s appendix.
Appendix
| Date | Model | Max Context (tokens) | Source |
|---|---|---|---|
| Jun 2017 | Transformer (Vaswani et al.) | 512 | Vaswani et al. (2017) |
| Jun 2018 | GPT-1 (Radford et al.) | 512 | Radford et al. (2018) |
| Feb 2019 | GPT-2 (Radford et al.) | 1,024 | Radford et al. (2019) |
| May 2020 | GPT-3 (Brown et al.) | 2,048 | Brown et al. (2020) |
| Jul 2021 | Codex (Chen et al.) | 4,096 | Chen et al. (2021) |
| Nov 2022 | ChatGPT / GPT-3.5 | 4,096–8,192 | OpenAI (2022) |