2505.20674

# Pretraining Language Models to Ponder in Continuous Space > Zhouhan Lin is the corresponding author. Abstract Humans ponder before articulating complex sentence elements, enabling deeper cognitive processing through focused effort. In this work, we introduce this pondering process into language models by repeatedly invoking the forward process within a single token generation step. During pondering, instead of generating an actual token sampled from the prediction distribution, the model ponders by yielding a weighted sum of all token embeddings according to the predicted token distribution. The generated embedding is then fed back as input for another forward pass. We show that the model can learn to ponder in this way through self-supervised learning, without any human annotations. Experiments across three widely used open-source architectures—GPT-2, Pythia, and LLaMA—and extensive downstream task evaluations demonstrate the effectiveness and generality of our method. For language modeling tasks, pondering language models achieve performance comparable to vanilla models with twice the number of parameters. On 9 downstream benchmarks, our pondering-enhanced Pythia models significantly outperform the official Pythia models. Notably, PonderingPythia-2.8B surpasses Pythia-6.9B, and PonderingPythia-1B is comparable to TinyLlama-1.1B, which is trained on 10 times more data. The code is available at https://github.com/LUMIA-Group/PonderingLM. 1 Introduction In the pursuit of improving model performance, scaling up model parameters and data sizes has long been the most widely adopted and accepted approach (Kaplan et al., 2020; Brown et al., 2020; Liu et al., 2024). However, this approach faces several bottlenecks, including the exhaustion of high-quality data (Villalobos et al., 2022; Muennighoff et al., 2023), the observed saturation in scaling laws (Hackenburg et al., 2025; Hoffmann et al., 2022a) and substantial communication overhead in distributed pre-training that grows super-linearly with model size (Narayanan et al., 2021; Pati et al., 2023; Li et al., 2024). On the other hand, if we look at humans, the growth of human capabilities does not stem from simply increasing the number of neurons in the brain. Instead, when faced with complex problems, humans often enhance their problem-solving abilities by repeatedly pondering, engaging in deep cognitive processing before articulating their thoughts. Analogously, in large language models, the most relevant research direction is test-time scaling. In particular, following the advancements in o1 and R1 (Jaech et al., 2024; DeepSeek-AI et al., 2025), generating long chains of thought (CoT) has emerged as the mainstream approach for scaling test-time computation. However, CoT-based methods also exhibit several drawbacks: they often require curated human-annotated datasets (Allen-Zhu & Li, 2023) and carefully designed reinforcement learning algorithms (Pang et al., 2025). Moreover, small models rarely benefit from CoT (Li et al., 2023), and the upper bound of performance remains constrained by the base pretrained model (Yue et al., 2025). Additionally, current language models employing CoT are still confined to discrete language spaces with fixed vocabularies, which, according to recent studies (Fedorenko et al., 2024; Hao et al., 2024; Pfau et al., 2024), are primarily optimized for communication rather than for internal computational thinking. To overcome these challenges and inspired by human pondering, we introduce the Pondering Language Model (Pondering LM), which relies solely on self-supervised learning. Pondering LMs can be naturally learned through pretraining on large-scale general corpora, without the need for human-annotated datasets or reinforcement learning. During pondering, instead of generating a discrete token sampled from the prediction distribution, the model produces a weighted sum of all token embeddings based on the predicted probabilities. This generated embedding is then fed back into the language model, allowing it to iteratively refine its predictions. As the weighted embedding is continuous, Pondering LMs overcome the expressive limitations of discrete token vocabularies and enable fully differentiable, end-to-end pretraining via gradient descent. Furthermore, by performing more computations per parameter, Pondering LMs achieve higher parameter knowledge density (Allen-Zhu & Li, 2024), potentially reducing communication costs at scale. Experimentally, by introducing the pondering process during pretraining, our Pondering GPT-2, LLaMA, and Pythia models achieve pretraining perplexity comparable to that of vanilla models with twice as many parameters. Furthermore, Pondering Pythia models significantly outperform the official Pythia models across nine popular downstream tasks, PonderingPythia-2.8B surpasses Pythia-6.9B, and PonderingPythia-1B is comparable to TinyLlama-1.1B, which is trained on 10 times more data. Notably, increasing the number of pondering steps consistently enhances model performance, underscoring the substantial potential of this approach. Moreover, our method is orthogonal to traditional scaling strategies, including parameter scaling and inference-time scaling via CoT, and thus can complement existing techniques, potentially introducing a third scaling axis to enhance model performance. <details> <summary>x1.png Details</summary>  ### Visual Description ## Diagram: Pondering Language Model Architecture ### Overview The image depicts a diagram of a Pondering Language Model architecture, showing the flow of information through multiple layers. It illustrates how input embeddings are processed through several "Pondering Language Model" blocks, with intermediate embeddings and word embeddings contributing to the final predicted probability. ### Components/Axes * **Text Labels:** * Predicted Probability (top-right) * Pondering Language Model (repeated three times) * Pondering Embedding (repeated twice) * Word Embed (repeated twice) * Input Embedding (bottom) * Vocabulary Size (right side, next to Word Embed) * Hidden Size (below Word Embed) * xN (right side, next to Word Embed) * **Shapes:** * Rectangular blocks (tan color) labeled "Pondering Language Model" * Rounded rectangles (tan color) labeled "Word Embed" * Rectangular blocks (light blue color) representing embeddings * Circles with a plus sign inside (⊕) representing addition operations * Arrows indicating the flow of information * **Numerical Values (Green Boxes):** * Top Layer: 0.6, ..., 0.2; 0.2, ..., 0.5; 0.7, ..., 0.1; 0.1, ..., 0.4; 0.8, ..., 0.1 * Middle Layer: 0.1, ..., 0.1; 0.2, ..., 0.4; 0.5, ..., 0.1; 0.1, ..., 0.2; 0.3, ..., 0.4 * Bottom Layer: 0.1, ..., 0.2; 0.2, ..., 0.2; 0.1, ..., 0.1; 0.3, ..., 0.2; 0.3, ..., 0.3 ### Detailed Analysis The diagram consists of three main "Pondering Language Model" blocks stacked vertically. 1. **Bottom Layer (Input):** * "Input Embedding" (light blue rectangle) feeds into the bottom "Pondering Language Model" block (tan rectangle). * The output of this block is represented by five green boxes, each containing two numerical values separated by ellipses. The values are: 0.1, ..., 0.2; 0.2, ..., 0.2; 0.1, ..., 0.1; 0.3, ..., 0.2; 0.3, ..., 0.3. * A "Pondering Embedding" (light blue rectangle) is added (⊕) to the output of each green box. * The "Word Embed" (tan rounded rectangle) is multiplied (⊙) by N. 2. **Middle Layer:** * The sum of the output of the bottom layer and the "Pondering Embedding" (light blue rectangle) feeds into the middle "Pondering Language Model" block (tan rectangle). * The output of this block is represented by five green boxes, each containing two numerical values separated by ellipses. The values are: 0.1, ..., 0.1; 0.2, ..., 0.4; 0.5, ..., 0.1; 0.1, ..., 0.2; 0.3, ..., 0.4. * A "Pondering Embedding" (light blue rectangle) is added (⊕) to the output of each green box. * The "Word Embed" (tan rounded rectangle) is multiplied (⊙) by N. 3. **Top Layer (Output):** * The sum of the output of the middle layer and the "Pondering Embedding" (light blue rectangle) feeds into the top "Pondering Language Model" block (tan rectangle). * The output of this block is represented by five green boxes, each containing two numerical values separated by ellipses. The values are: 0.6, ..., 0.2; 0.2, ..., 0.5; 0.7, ..., 0.1; 0.1, ..., 0.4; 0.8, ..., 0.1. * These values are labeled as "Predicted Probability". ### Key Observations * The diagram illustrates a multi-layered architecture where each layer consists of a "Pondering Language Model" block, an addition operation (⊕) with a "Pondering Embedding", and a multiplication operation (⊙) with a "Word Embed". * The numerical values in the green boxes represent intermediate probabilities or activations at different stages of the model. * The "Predicted Probability" values at the top layer represent the final output of the model. ### Interpretation The diagram represents a deep learning architecture for a language model. The "Pondering Language Model" blocks likely contain complex transformations of the input embeddings. The "Pondering Embedding" and "Word Embed" components suggest that the model is incorporating both contextual information (pondering) and lexical information (words) at each layer. The multiplication by N likely represents a scaling factor related to the vocabulary size or the number of words in the input sequence. The model iteratively refines its predictions through multiple layers, ultimately producing a "Predicted Probability" distribution. The ellipses (...) within the green boxes suggest that there are more values than are explicitly shown, possibly representing a vector of probabilities or activations. </details> ⬇ class PonderingLanguageModel (nn. Module): def __init__ (self, lm, v, h, k): self. lm = lm # language model self. vocab_size = v self. hidden_dim = h self. pondering_steps = k self. embedding = nn. Parameter (torch. randn (v, h), requires_grad = True) def forward (self, input_tokens): input_embedding = self. embedding [input_tokens] #Iterative pondering for t in range (self. pondering_steps): predicted_prob = self. lm (input_embedding) pondering_embedding = torch. matmul (predicted_prob, self. embedding) input_embedding = input_embedding + pondering_embedding #Final forward pass final_prob = self. lm (input_embedding) return final_prob Figure 1: Overview of the Pondering Language Model. Given input token embeddings, the base LM produces a probability distribution over the vocabulary, which is used to compute a continuous “pondering embedding” via a weighted sum of all token embeddings. This embedding is then added residually to the original input embeddings and fed back into the LM. By repeating this process for $k$ steps within a single token prediction, the model iteratively refines its output distributions. The pseudocode on the right illustrates the implementation details. 2 Pondering Language Model In this section, we introduce our proposed Pondering Language Model (Figure 1), which integrates a pondering mechanism into language models via pretraining. Given that pretraining fundamentally constitutes a language modeling task, we briefly review this task before detailing our proposed model. Language Modeling. Given a sequence of tokens $X=[x_{1},x_{2},...,x_{n}]$ , the primary objective of language modeling is typically to maximize the likelihood of predicting each token based on its preceding tokens. Formally, this is expressed through the joint probability factorization: $$ P(x_{1},x_{2},\dots,x_{n})=\prod_{t=1}^{n}P(x_{t}\mid x_{<t}) \tag{1} $$ Current language models first map tokens to input embeddings $\mathbf{E}^{0}=[\mathbf{e}^{0}_{1},\mathbf{e}^{0}_{2},...,\mathbf{e}^{0}_{n}]$ , where each embedding $\mathbf{e}^{0}_{i}∈\mathbb{R}^{d}$ is selected from a vocabulary embedding matrix $\mathbf{V}=[\mathbf{e}_{1},\mathbf{e}_{2},...,\mathbf{e}_{|V|}]$ , with vocabulary size $|V|$ and hidden dimension $d$ . The language model then generates output probabilities $\mathbf{P}$ for predicting the next token at each position: $$ \mathbf{P}=\text{LM}(\mathbf{E}^{0}),\quad\mathbf{P}\in\mathbb{R}^{n\times|V|} \tag{2} $$ The cross-entropy loss is computed directly from these predicted probabilities $\mathbf{P}$ to pretrain the language model. Pondering Mechanism. In our proposed method, instead of directly using the predicted output probabilities $\mathbf{P}$ to compute the cross-entropy loss, we utilize these probabilities as weights to sum embeddings of all candidate tokens, forming what we call a "pondering embedding". Given the probability distribution $\mathbf{p}∈\mathbb{R}^{|V|}$ at each position, the pondering embedding $\mathbf{t}$ is: $$ \mathbf{t}=\sum_{i=1}^{|V|}p_{i}\mathbf{e}_{i},\quad p_{i}\in\mathbb{R},% \mathbf{e}_{i}\in\mathbb{R}^{d} \tag{3} $$ For computational efficiency, pondering embeddings $\mathbf{t}$ for all positions can be calculated simultaneously via matrix multiplication In practice, we use only the top-K tokens with highest probabilities at each position to compute the pondering embedding, reducing complexity from $\mathcal{O}(n|V|d)$ to $\mathcal{O}(nKd)$ . With $K=100\ll|V|$ , this does not degrade LM performance and makes the matrix multiplication overhead negligible within the overall LM computations. : $$ \mathbf{T}=\mathbf{P}\mathbf{V},\quad\mathbf{T}\in\mathbb{R}^{n\times d} \tag{4} $$ Through these pondering embeddings, we effectively map predicted probabilities back into the embedding space, preserving embedding information from all possible candidate tokens. To maintain the information from the original input embeddings, we integrate the pondering embeddings using a residual connection: $$ \mathbf{E}^{1}=\mathbf{E}^{0}+\mathbf{T}=[\mathbf{e}^{0}_{1}+\mathbf{t}_{1},% \mathbf{e}^{0}_{2}+\mathbf{t}_{2},\dots,\mathbf{e}^{0}_{n}+\mathbf{t}_{n}] \tag{5} $$ We then feed the updated embeddings $\mathbf{E}^{1}$ back into the same language model to obtain refined output probabilities: $$ \mathbf{P}^{1}=\text{LM}(\mathbf{E}^{1}),\quad\mathbf{P}^{1}\in\mathbb{R}^{n% \times|V|} \tag{6} $$ After obtaining $\mathbf{P}^{1}$ , we can iteratively repeat the previous process to achieve multi-step pondering. Specifically, given a predefined number of pondering steps $k$ Unless otherwise specified, we set $k=3$ for subsequent experiments., we iteratively compute new pondering embeddings and integrate them with the original input embeddings using residual connections, feeding the result back into the same language model until $k$ steps are reached: $$ \displaystyle\mathbf{E}^{0} \displaystyle=[\mathbf{e}^{0}_{1},\mathbf{e}^{0}_{2},\dots,\mathbf{e}^{0}_{n}]% ,\quad\mathbf{P}^{0}=\text{LM}(\mathbf{E}^{0}),\quad\mathbf{T}^{1}=\mathbf{P}^% {0}\mathbf{V} \displaystyle\mathbf{E}^{1} \displaystyle=\mathbf{E}^{0}+\mathbf{T}^{1}=[\mathbf{e}^{0}_{1}+\mathbf{t}^{1}% _{1},\mathbf{e}^{0}_{2}+\mathbf{t}^{1}_{2},\dots,\mathbf{e}^{0}_{n}+\mathbf{t}% ^{1}_{n}],\quad\mathbf{P}^{1}=\text{LM}(\mathbf{E}^{1}),\quad\mathbf{T}^{2}=% \mathbf{P}^{1}\mathbf{V} \displaystyle\dots \displaystyle\mathbf{E}^{k} \displaystyle=\mathbf{E}^{0}+\sum_{i=1}^{k}\mathbf{T}^{i}=[\mathbf{e}^{0}_{1}+% \mathbf{t}^{1}_{1}+\dots+\mathbf{t}^{k}_{1},\dots,\mathbf{e}^{0}_{n}+\mathbf{t% }^{1}_{n}+\dots+\mathbf{t}^{k}_{n}],\quad\mathbf{P}^{k}=\text{LM}(\mathbf{E}^{% k}) \tag{7} $$ This iterative pondering mechanism progressively refines the model’s predictions. Finally, we can use the refined output probabilities $\mathbf{P}^{k}$ after $k$ pondering steps to compute the cross-entropy loss and optimize the language model to perform $k$ -step pondering. 3 Experiments Our experiments consist of four parts. First, we validate the scaling curves of pondering models on widely used GPT-2 and LLaMA architectures. Second, we perform large-scale pretraining of PonderingPythia models on the Pile dataset and compare their scaling curves and language modeling capabilities with those of the official Pythia suite (Biderman et al., 2023). Third, we evaluate the downstream task performance of PonderingPythia models, including nine popular general tasks and an instruction-following task, and compare the results with official Pythia, OPT (Zhang et al., 2022), Bloom (Le Scao et al., 2023), GPT-Neo (Black et al., 2021), and TinyLLaMA (Zhang et al., 2024) models. Finally, we investigate the impact of the number of pondering steps on pretraining perplexity. 3.1 Small Scale Validation on GPT-2 and LLaMA We apply our proposed method to two popular Transformer architectures, GPT-2 and LLaMA, to investigate its general applicability and effectiveness. Specifically, we plot and compare scaling curves between vanilla GPT-2, vanilla LLaMA, and their corresponding pondering versions, referred to as PonderingGPT and PonderingLLaMA, respectively. Experimental Settings. We train all models from scratch on a subset of the Pile dataset with the same tokenizer. The model sizes range from 405M to 1.4B parameters, with a context length fixed at 2048 tokens. The number of training tokens for each model is chosen to approximately match the scaling laws proposed by Chinchilla (Hoffmann et al., 2022b). The detailed configurations of the models, including sizes, learning rates, and batch sizes, are specified in Table 1. These hyperparameters primarily follow the GPT-3 specifications (Brown et al., 2020). However, unlike GPT-3, we untie the input and output embedding matrices. Table 1: Model sizes and hyperparameters for scaling experiments. | params | $\mathrm{n_{layers}}$ | $\mathrm{d_{model}}$ | $\mathrm{n_{heads}}$ | learning rate | batch size (in tokens) | tokens | | --- | --- | --- | --- | --- | --- | --- | | 405M | 24 | 1024 | 16 | 3e-4 | 0.5M | 7B | | 834M | 24 | 1536 | 24 | 2.5e-4 | 0.5M | 15B | | 1.4B | 24 | 2048 | 32 | 2e-4 | 0.5M | 26B | <details> <summary>x2.png Details</summary>  ### Visual Description ## Chart: Loss vs. Model Size ### Overview The image is a line chart comparing the loss of different language models (GPT, LLaMA, Pondering GPT, and Pondering LLaMA) across varying model sizes (405M*7B, 834M*15B, and 1.4B*26B). It also shows the difference in loss between GPT and LLaMA, GPT and Pondering GPT, and LLaMA and Pondering LLaMA. ### Components/Axes * **Y-axis (left)**: "Loss", ranging from 2.1 to 2.6 in increments of 0.1. * **X-axis (bottom)**: Model sizes: "405M*7B", "834M*15B", and "1.4B*26B". * **Lower Y-axis (left)**: "ΔLoss", ranging from 0.05 to 0.15 in increments of 0.05. * **Legend (top-right)**: * "GPT fitted" (dashed blue line) * "LLaMA fitted" (dashed green line) * "GPT" (solid blue line with circle markers) * "LLaMA" (solid green line with circle markers) * "Pondering GPT" (solid blue line with star markers) * "Pondering LLaMA" (solid green line with star markers) * "L_GPT - L_LLaMA" (dashed black line with triangle markers) * "L_GPT - L_PonderingGPT" (solid blue line with triangle markers) * "L_LLaMA - L_{PonderingLLaMA}" (solid green line with triangle markers) ### Detailed Analysis **Main Chart (Loss vs. Model Size):** * **GPT (solid blue line with circle markers):** Decreases from approximately 2.62 at 405M*7B to approximately 2.19 at 1.4B*26B. * **LLaMA (solid green line with circle markers):** Decreases from approximately 2.54 at 405M*7B to approximately 2.18 at 1.4B*26B. * **Pondering GPT (solid blue line with star markers):** Decreases from approximately 2.48 at 405M*7B to approximately 2.09 at 1.4B*26B. * **Pondering LLaMA (solid green line with star markers):** Decreases from approximately 2.45 at 405M*7B to approximately 2.10 at 1.4B*26B. * **GPT fitted (dashed blue line):** Decreases from approximately 2.6 at 405M*7B to approximately 2.2 at 1.4B*26B. * **LLaMA fitted (dashed green line):** Decreases from approximately 2.55 at 405M*7B to approximately 2.17 at 1.4B*26B. **Difference Chart (ΔLoss):** * **L_GPT - L_LLaMA (dashed black line with triangle markers):** Decreases slightly from approximately 0.07 at 405M*7B to approximately 0.02 at 1.4B*26B. * **L_GPT - L_PonderingGPT (solid blue line with triangle markers):** Remains relatively constant at approximately 0.13-0.10 across all model sizes. * **L_LLaMA - L_{PonderingLLaMA} (solid green line with triangle markers):** Remains relatively constant at approximately 0.10-0.09 across all model sizes. **Annotations:** * An arrow points from the LLaMA line at 834M*15B to the LLaMA line at 1.4B*26B, labeled "2.01x". * An arrow points from the Pondering LLaMA line at 834M*15B to the Pondering LLaMA line at 1.4B*26B, labeled "2.26x". ### Key Observations * All models show a decrease in loss as the model size increases. * Pondering GPT and Pondering LLaMA consistently have lower loss than GPT and LLaMA, respectively. * The difference in loss between GPT and LLaMA decreases as the model size increases. * The difference in loss between GPT and Pondering GPT, and LLaMA and Pondering LLaMA, remains relatively constant across all model sizes. * The "fitted" lines are very close to the original lines. ### Interpretation The chart demonstrates that increasing model size generally leads to lower loss for all models tested (GPT, LLaMA, and their "Pondering" variants). The "Pondering" versions of the models consistently outperform their non-pondering counterparts, suggesting that the "Pondering" technique is effective in reducing loss. The decreasing difference in loss between GPT and LLaMA as model size increases suggests that the two models converge in performance as they scale. The annotations "2.01x" and "2.26x" likely refer to the relative improvement in some metric (possibly perplexity or another measure of language modeling performance) between the 834M*15B and 1.4B*26B model sizes for LLaMA and Pondering LLaMA, respectively. The "fitted" lines likely represent a smoothed or regression-based representation of the original data. </details> Figure 2: (top) Scaling curves of GPT3 LLaMA and their corresponding pondering models. (bottom) Relative improvements of RoPE + RMSNorm + SwiGLU MLP and Pondering. Results. Figure 2 (top) illustrates the scaling curves of the validation loss on the Pile subset for vanilla GPT-2, vanilla LLaMA, and their pondering counterparts. Our results show that incorporating pondering significantly improves the performance for both GPT-2 and LLaMA across the entire size range tested (405M to 1.4B parameters). For instance, by fitting scaling curves, we find that PonderingGPT-834M achieves a loss comparable to a vanilla GPT-2 model trained with approximately $2.01×$ parameters $*$ tokens, while PonderingLLaMA-834M matches the loss of vanilla LLaMA trained with roughly $2.26×$ parameters $*$ tokens. Furthermore, Figure 2 (bottom) shows the relative validation loss improvements (denoted as $\Delta$ loss) of architectural modifications inherent in LLaMA—namely rotary positional embeddings (RoPE) (Su et al., 2024), RMSNorm (Zhang & Sennrich, 2019), and SwiGLU activation—in comparison to GPT-2, alongside the relative improvements obtained by our pondering method for both architectures. We observe that while the relative improvement due to RoPE, RMSNorm, and SwiGLU MLP diminishes as model size and data scale increase (reaching approximately 0.02 for the 1.4B parameter model), the relative improvement provided by pondering consistently remains around 0.1 across the entire tested scale. <details> <summary>x3.png Details</summary>  ### Visual Description ## Chart: Loss vs. Number of Parameters ### Overview The image is a line chart comparing the loss of two models, "Pythia" and "PonderingPythia," as a function of the number of parameters. The x-axis represents the number of parameters on a logarithmic scale, and the y-axis represents the loss. The chart includes data points for each model and smoothed lines connecting these points. ### Components/Axes * **Title:** There is no explicit title on the chart. * **X-axis:** * Label: "#Parameters (log scale)" * Scale: 200M, 500M, 1B, 2B, 3B, 7B (logarithmic scale) * **Y-axis:** * Label: "Loss" * Scale: 1.8 to 2.5, with increments of 0.1 * **Legend:** Located in the top-right corner. * Blue line: Pythia * Green line: PonderingPythia * Blue dots: Pythia * Green dots: PonderingPythia * **Annotation:** "37% params" with a purple arrow pointing from 3B to the Pythia line at approximately loss 1.85. ### Detailed Analysis * **Pythia (Blue):** * Trend: The loss decreases as the number of parameters increases. * Data Points: * 200M: Approximately 2.55 * 500M: Approximately 2.18 * 1B: Approximately 2.06 * 2B: Approximately 1.98 * 7B: Approximately 1.84 * **PonderingPythia (Green):** * Trend: The loss decreases as the number of parameters increases. * Data Points: * 200M: Approximately 2.30 * 500M: Approximately 2.10 * 1B: Approximately 1.97 * 2B: Approximately 1.91 * 3B: Approximately 1.88 * **Annotation:** * The purple arrow indicates that using 37% of the parameters of the Pythia model at 7B parameters, the PonderingPythia model achieves a similar loss. ### Key Observations * Both models exhibit a decrease in loss as the number of parameters increases. * PonderingPythia consistently shows a lower loss than Pythia for the same number of parameters. * The rate of decrease in loss diminishes as the number of parameters increases for both models. * The annotation highlights that PonderingPythia can achieve a similar loss to Pythia with significantly fewer parameters. ### Interpretation The chart demonstrates the relationship between model size (number of parameters) and performance (loss) for two different models, Pythia and PonderingPythia. The data suggests that PonderingPythia is more efficient, achieving lower loss values with fewer parameters compared to Pythia. The annotation "37% params" emphasizes this efficiency, indicating that PonderingPythia can match Pythia's performance with a significantly smaller model size. This could imply that PonderingPythia has a more efficient architecture or training process. The diminishing returns in loss reduction as parameters increase suggest that there is a point of diminishing returns in simply scaling up model size. </details> <details> <summary>x4.png Details</summary>  ### Visual Description ## Chart: Loss vs. Training Tokens (Log Scale) ### Overview The image is a line chart comparing the loss of two models, "Pythia-1B" and "PonderingPythia-1B", as a function of the number of training tokens (on a log scale). The chart also includes a horizontal line indicating the loss achieved by "PonderingPythia-1B" after 41% of the training tokens. ### Components/Axes * **X-axis:** "#Training tokens (log scale)". The axis is marked with values 60B, 100B, 200B, and 280B. * **Y-axis:** "Loss". The axis is marked with values 1.95, 2.00, 2.05, 2.10, 2.15, 2.20, and 2.25. * **Legend (top-right):** * Blue line: Pythia-1B * Green line: PonderingPythia-1B * Blue dots: Pythia-1B * Green dots: PonderingPythia-1B * **Annotation:** "41% training tokens" (purple text with a purple horizontal line). ### Detailed Analysis * **Pythia-1B (Blue):** The blue line represents the loss of the Pythia-1B model. The line slopes downward, indicating a decrease in loss as the number of training tokens increases. * At 60B tokens, the loss is approximately 2.21. * At 100B tokens, the loss is approximately 2.17. * At 200B tokens, the loss is approximately 2.11. * At 280B tokens, the loss is approximately 2.06. * **PonderingPythia-1B (Green):** The green line represents the loss of the PonderingPythia-1B model. The line slopes downward, indicating a decrease in loss as the number of training tokens increases. * At 60B tokens, the loss is approximately 2.12. * At 100B tokens, the loss is approximately 2.09. * At 200B tokens, the loss is approximately 1.99. * At 280B tokens, the loss is approximately 1.97. * **41% training tokens (Purple):** The purple horizontal line indicates the loss achieved by PonderingPythia-1B at 41% of the total training tokens. The line intersects the green line at approximately 100B tokens and a loss of approximately 2.06. ### Key Observations * Both models show a decrease in loss as the number of training tokens increases. * PonderingPythia-1B consistently has a lower loss than Pythia-1B for the same number of training tokens. * The annotation indicates that PonderingPythia-1B achieves a certain loss level (approximately 2.06) at 41% of the total training tokens. ### Interpretation The chart demonstrates the relationship between the number of training tokens and the loss of two language models. The downward trend of both lines suggests that increasing the number of training tokens improves the performance of both models, as indicated by the reduction in loss. The fact that PonderingPythia-1B consistently outperforms Pythia-1B suggests that the "pondering" mechanism is effective in reducing loss. The annotation highlights the efficiency of PonderingPythia-1B, showing that it achieves a certain level of performance with significantly fewer training tokens compared to the total amount used. This could imply that PonderingPythia-1B learns more effectively or requires less data to reach a comparable level of performance. </details> <details> <summary>x5.png Details</summary>  ### Visual Description ## Line Chart: Loss vs. FLOPS for Vanilla and Pondering Pythia-70M ### Overview The image is a line chart comparing the loss of two language models, "Vanilla Pythia-70M" and "Pondering Pythia-70M", as a function of FLOPS (EFLOPs). The x-axis represents FLOPS (EFLOPs), and the y-axis represents Loss. Both models show a decrease in loss as FLOPS increase, but "Pondering Pythia-70M" consistently exhibits lower loss values than "Vanilla Pythia-70M". ### Components/Axes * **Title:** Implicit, but the chart compares the performance of "Vanilla Pythia-70M" and "Pondering Pythia-70M". * **X-axis:** FLOPS (EFLOPs) * Scale: 100, 200, 300, 400 * **Y-axis:** Loss * Scale: 2.55, 2.60, 2.65, 2.70, 2.75 * **Legend:** Located in the top-right corner. * Blue line with circle markers: Vanilla Pythia-70M * Green line with circle markers: Pondering Pythia-70M ### Detailed Analysis * **Vanilla Pythia-70M (Blue):** The loss decreases as FLOPS increase. * At 75 EFLOPs, Loss is approximately 2.78. * At 150 EFLOPs, Loss is approximately 2.76. * At 225 EFLOPs, Loss is approximately 2.75. * At 300 EFLOPs, Loss is approximately 2.74. * At 400 EFLOPs, Loss is approximately 2.73. * At 450 EFLOPs, Loss is approximately 2.72. * **Pondering Pythia-70M (Green):** The loss decreases as FLOPS increase. * At 75 EFLOPs, Loss is approximately 2.67. * At 150 EFLOPs, Loss is approximately 2.62. * At 225 EFLOPs, Loss is approximately 2.60. * At 300 EFLOPs, Loss is approximately 2.58. * At 400 EFLOPs, Loss is approximately 2.55. * At 450 EFLOPs, Loss is approximately 2.54. ### Key Observations * Both models exhibit a decreasing loss trend as FLOPS increase. * "Pondering Pythia-70M" consistently outperforms "Vanilla Pythia-70M" in terms of loss at all FLOPS values. * The rate of loss decrease appears to diminish as FLOPS increase for both models. ### Interpretation The chart demonstrates that increasing the computational resources (FLOPS) leads to a reduction in loss for both "Vanilla Pythia-70M" and "Pondering Pythia-70M" language models. The "Pondering Pythia-70M" model consistently achieves lower loss values compared to the "Vanilla Pythia-70M" model, suggesting that the "Pondering" architecture is more efficient or effective in reducing loss for a given amount of computation. The diminishing rate of loss decrease suggests that there may be a point of diminishing returns in increasing FLOPS for these models. </details> Figure 3: Language modeling loss when scaling parameter count and training tokens. PonderingPythia achieves comparable performance to the official Pythia-6.9B while using only 37% of the parameters, and matches the performance of the official Pythia-1B with just 41% of the training tokens. Table 2: Language Modeling Perplexity (ppl). Lower is better. The values in parentheses indicate the improvement ( $\downarrow$ ) compared to the corresponding Pythia model. For simplicity, we refer to PonderingPythia as Ponder. | Model | Pile | Wikitext | Lambada Openai | Lambada Standard | | --- | --- | --- | --- | --- | | Pythia-70M | $18.36$ | $57.03$ | $141.94$ | $967.72$ | | Ponder-70M | $12.68$ ( $\downarrow$ 5.68) | $34.07$ ( $\downarrow$ 22.96) | $39.19$ ( $\downarrow$ 102.75) | $145.51$ ( $\downarrow$ 822.21) | | Pythia-160M | $12.55$ | $33.43$ | $38.15$ | $186.51$ | | Ponder-160M | $9.87$ ( $\downarrow$ 2.68) | $23.69$ ( $\downarrow$ 9.74) | $15.96$ ( $\downarrow$ 22.19) | $41.24$ ( $\downarrow$ 145.27) | | Pythia-410M | $8.85$ | $20.11$ | $10.86$ | $31.54$ | | Ponder-410M | $8.15$ ( $\downarrow$ 0.70) | $17.78$ ( $\downarrow$ 2.33) | $8.55$ ( $\downarrow$ 2.31) | $17.48$ ( $\downarrow$ 14.06) | | Pythia-1B | $7.85$ | $16.45$ | $7.91$ | $17.41$ | | Ponder-1B | $7.15$ ( $\downarrow$ 0.70) | $14.61$ ( $\downarrow$ 1.84) | $6.02$ ( $\downarrow$ 1.89) | $10.64$ ( $\downarrow$ 6.77) | | Pythia-1.4B | $7.24$ | $14.72$ | $6.08$ | $10.87$ | | Ponder-1.4B | $6.82$ ( $\downarrow$ 0.42) | $13.59$ ( $\downarrow$ 1.13) | $5.37$ ( $\downarrow$ 0.71) | $8.88$ ( $\downarrow$ 1.99) | | Pythia-2.8B | $6.63$ | $12.69$ | $5.04$ | $8.23$ | | Ponder-2.8B | $6.21$ ( $\downarrow$ 0.42) | $11.74$ ( $\downarrow$ 0.95) | $4.15$ ( $\downarrow$ 0.89) | $6.17$ ( $\downarrow$ 2.06) | | Pythia-6.9B | $6.29$ | $11.41$ | $4.45$ | $6.95$ | 3.2 Large-Scale Pretraining on Pile We further validate the effectiveness of our pondering method by conducting large-scale pretraining experiments on the entire Pile dataset (300B tokens) (Gao et al., 2020). We train a new model, named PonderingPythia, from scratch using exactly the same architectural components (parallel attention and MLP layers, rotary embeddings with 1/4 head dimensions), same tokenizer and training hyperparameters (optimizer settings, learning rate schedule, batch size, and context length) as the original Pythia models. We then compare PonderingPythia models’ scaling curves and language modeling capabilities with the official Pythia model suite. 3.2.1 Scaling Curves We plot the PonderingPythia and official Pythia model’s scaling curves along parameters size, training tokens and training flops. As depicted in Figure 3 (left), the fitted curves show that a 2.5B-parameter PonderingPythia model achieves a validation loss comparable to the 6.9B-parameter official Pythia model, while requiring only 37% of the parameters. In Figure 3 (middle), we evaluated the 1B PonderingPythia and official Pythia models at intervals of 20B training tokens. The fitted curves indicate that PonderingPythia trained with 115B tokens achieves performance comparable to the official Pythia model trained with 280B tokens, consuming only 41% of the training tokens. In Figure 3 (right), we report the language modeling loss of vanilla Pythia-70M To match the training FLOPs of vanilla Pythia-70M with PonderingPythia-70M, we trained the vanilla model for 4 epochs. and PonderingPythia-70M under the same computational budget during pretraining. It can be observed that PonderingPythia-70M consistently outperforms vanilla Pythia-70M when trained with the same number of FLOPs. 3.2.2 Language Modeling Ability Evaluation We measure the perplexity on several language modeling datasets to reflect general language modeling capabilities. Specifically, we report perplexity scores on the Pile validation set, Wikitext, and the Lambada dataset (both OpenAI and standard versions), detailed in Table 2. The results demonstrate significant perplexity improvements across all datasets and model sizes. Notably, the perplexity achieved by the PonderingPythia-2.8B model is even better than that of the official Pythia-6.8B model, which is nearly 2.5 times larger. 3.3 Downstream Tasks Evaluation We use the PonderingPythia models pretrained in the previous subsection to conduct downstream task evaluations. <details> <summary>x6.png Details</summary>  ### Visual Description ## Radar Chart: Model Performance Comparison ### Overview The image is a radar chart comparing the performance of two models, "Pythia-1B" and "PonderingPythia-1B," across several categories: Writing, Roleplay, Reasoning, Math, Coding, Extraction, STEM, and Humanities. The chart visualizes the strengths and weaknesses of each model in these categories, with scores ranging from 0 to 3. ### Components/Axes * **Categories (Axes):** Writing, Roleplay, Reasoning, Math, Coding, Extraction, STEM, Humanities. These are arranged radially around the chart. * **Scale:** The radial scale ranges from 0 to 3, with increments of 0.5. * **Data Series:** * Pythia-1B (blue line, avg score=1.89) * PonderingPythia-1B (green line, avg score=2.22) * **Legend:** Located at the bottom of the chart, it identifies the models and their corresponding colors. ### Detailed Analysis Here's a breakdown of the performance of each model in each category: * **Writing:** * Pythia-1B: Approximately 1.9 * PonderingPythia-1B: Approximately 2.7 * **Roleplay:** * Pythia-1B: Approximately 1.8 * PonderingPythia-1B: Approximately 2.1 * **Reasoning:** * Pythia-1B: Approximately 1.5 * PonderingPythia-1B: Approximately 1.6 * **Math:** * Pythia-1B: Approximately 1.2 * PonderingPythia-1B: Approximately 1.4 * **Coding:** * Pythia-1B: Approximately 0.8 * PonderingPythia-1B: Approximately 1.1 * **Extraction:** * Pythia-1B: Approximately 0.7 * PonderingPythia-1B: Approximately 1.6 * **STEM:** * Pythia-1B: Approximately 1.0 * PonderingPythia-1B: Approximately 2.0 * **Humanities:** * Pythia-1B: Approximately 1.5 * PonderingPythia-1B: Approximately 2.3 ### Key Observations * PonderingPythia-1B consistently outperforms Pythia-1B across all categories. * Both models show relatively high performance in Writing and Roleplay. * Both models show relatively low performance in Coding and Extraction. * The largest performance difference between the two models is in STEM and Extraction. ### Interpretation The radar chart provides a clear visual comparison of the two models' capabilities. PonderingPythia-1B demonstrates a higher average score (2.22) compared to Pythia-1B (1.89), indicating an overall better performance. The chart highlights specific areas where PonderingPythia-1B excels, particularly in STEM and Extraction, suggesting that modifications made in "PonderingPythia-1B" have significantly improved its performance in these areas. The relatively lower scores in Coding and Extraction for both models suggest these are areas that could benefit from further development and refinement. The data suggests that "PonderingPythia-1B" is a more well-rounded model with improvements across the board, but both models have areas for potential improvement. </details> <details> <summary>x7.png Details</summary>  ### Visual Description ## Radar Chart: Model Performance Comparison ### Overview The image is a radar chart comparing the performance of two models, "Pythia-1.4B" and "PonderingPythia-1.4B", across several categories: Writing, Roleplay, Reasoning, Math, Coding, Extraction, STEM, and Humanities. The chart visualizes the strengths and weaknesses of each model in these different areas. ### Components/Axes * **Axes:** The chart has eight axes, each representing a different category: Writing, Roleplay, Reasoning, Math, Coding, Extraction, STEM, and Humanities. * **Scale:** The radial scale ranges from 0 to 3.5, with increments of 0.5. * **Legend:** Located at the bottom of the chart: * Blue line: Pythia-1.4B, avg score = 2.2 * Green line: PonderingPythia-1.4B, avg score = 2.75 ### Detailed Analysis * **Pythia-1.4B (Blue Line):** * Writing: Approximately 2.0 * Roleplay: Approximately 2.3 * Reasoning: Approximately 2.3 * Math: Approximately 1.8 * Coding: Approximately 1.2 * Extraction: Approximately 1.5 * STEM: Approximately 1.7 * Humanities: Approximately 1.8 The Pythia-1.4B model shows relatively consistent performance across all categories, with slightly higher scores in Roleplay and Reasoning. * **PonderingPythia-1.4B (Green Line):** * Writing: Approximately 3.5 * Roleplay: Approximately 3.0 * Reasoning: Approximately 2.5 * Math: Approximately 1.9 * Coding: Approximately 1.4 * Extraction: Approximately 1.0 * STEM: Approximately 2.5 * Humanities: Approximately 3.0 The PonderingPythia-1.4B model excels in Writing, Roleplay, Humanities, and STEM, but performs relatively weaker in Extraction and Coding. ### Key Observations * PonderingPythia-1.4B consistently outperforms Pythia-1.4B in Writing, Roleplay, Humanities, and STEM. * Both models have relatively lower scores in Coding and Extraction. * PonderingPythia-1.4B has a higher average score (2.75) compared to Pythia-1.4B (2.2). ### Interpretation The radar chart provides a clear visual comparison of the two models' capabilities across different domains. PonderingPythia-1.4B appears to be a more versatile model, particularly strong in creative and knowledge-based tasks (Writing, Roleplay, Humanities) and STEM, while Pythia-1.4B offers a more balanced performance profile. The lower scores in Coding and Extraction for both models suggest potential areas for improvement in future iterations. The higher average score of PonderingPythia-1.4B indicates that it is generally a better-performing model overall. </details> Figure 4: Instruction-following abilities evaluated on MT-Bench. PonderingPythia-1B and 1.4B consistently outperform their corresponding official Pythia models across all subtasks. 3.3.1 General Downstream Tasks We consider various widely-used benchmarks, including the tasks originally used by Pythia (LAMBADA (Paperno et al., 2016), PIQA (Bisk et al., 2020), WinoGrande (Sakaguchi et al., 2021), ARC-Easy and ARC-Challenge (Clark et al., 2018), SciQ (Welbl et al., 2017). Additionally, we include HellaSwag (Zellers et al., 2019) for commonsense reasoning and RACE (Lai et al., 2017) for reading comprehension. We evaluate both zero-shot and five-shot learning performance using the LM evaluation harness (Gao et al., 2023). Detailed results are shown in Table 3. Across all evaluated model sizes, PonderingPythia consistently and significantly outperforms the official Pythia models, as well as comparable OPT, GPT-Neo, and Bloom models. Remarkably, with only 1/10 of the training data (300B tokens) and fewer parameters (1B vs. 1.1B), our PonderingPythia-1B achieves results comparable to, or even surpassing, TinyLlama—which uses a more advanced LLaMA architecture and 3T tokens. PonderingPythia-2.8B also surpasses Pythia-6.9B, which is nearly 2.5 times its size. Table 3: Five-shot and zero-shot evaluations on downstream NLP tasks. All pretrained model weights used for comparison are obtained from their official repositories. We refer to PonderingPythia as Ponder for simplicity. $\Delta$ acc is compared to the official Pythia models. | Model (#training tokens) | Lambada OpenAI | ARC -E | Lambada Standard | ARC -C | Wino Grande | PIQA | Hella Swag | SciQ | RACE | Avg acc / $\Delta$ acc $\uparrow$ | | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | | 5-shot | | | | | | | | | | | | Pythia-70M (300B) | 11.9 | 36.7 | 9.2 | 17.1 | 50.5 | 58.7 | 26.7 | 57.8 | 25.1 | 32.6 | | Ponder-70M (300B) | 28.4 | 44.6 | 21.1 | 18.6 | 52.2 | 62.4 | 28.4 | 75.7 | 26.9 | 39.8 / +7.2 | | Pythia-160M (300B) | 24.9 | 44.7 | 19.0 | 18.4 | 50.4 | 63.5 | 28.6 | 76.4 | 27.8 | 39.3 | | OPT-125M (300B) | 29.8 | 42.3 | 26.4 | 19.7 | 51.3 | 63.4 | 29.0 | 78.8 | 30.1 | 41.2 | | GPTneo-125M (300B) | 29.3 | 43.9 | 23.0 | 19.1 | 51.9 | 63.9 | 28.5 | 79.9 | 27.9 | 40.8 | | Ponder-160M (300B) | 39.9 | 50.1 | 31.2 | 22.1 | 51.2 | 65.8 | 31.9 | 85.4 | 30.1 | 45.3 / +6.0 | | Pythia-410M (300B) | 43.9 | 54.7 | 32.8 | 22.3 | 53.4 | 68.0 | 33.8 | 88.9 | 30.4 | 47.6 | | OPT-350M (300B) | 38.3 | 45.4 | 32.1 | 20.5 | 53.0 | 65.8 | 31.9 | 85.7 | 29.5 | 44.7 | | Bloom-560M (366B) | 29.4 | 50.2 | 29.7 | 21.9 | 52.7 | 64.2 | 31.4 | 88.0 | 30.0 | 44.2 | | Ponder-410M (300B) | 48.9 | 58.7 | 43.7 | 26.1 | 54.0 | 70.5 | 37.3 | 91.0 | 32.4 | 51.4 /+3.8 | | Pythia-1B (300B) | 48.3 | 58.6 | 35.8 | 25.4 | 52.8 | 71.3 | 37.7 | 91.6 | 31.7 | 50.4 | | OPT-1.3B (300B) | 54.0 | 60.4 | 49.0 | 26.9 | 56.9 | 72.4 | 38.5 | 91.8 | 35.4 | 52.7 | | GPTneo-1.3B (300B) | 49.9 | 59.9 | 44.5 | 25.9 | 56.6 | 71.6 | 38.6 | 86.1 | 34.5 | 51.9 | | Bloom-1.1B (366B) | 36.3 | 54.9 | 37.4 | 24.9 | 53.4 | 67.6 | 34.8 | 88.7 | 33.0 | 47.9 | | Ponder-1B (300B) | 57.7 | 63.2 | 52.5 | 28.6 | 58.6 | 73.3 | 41.9 | 93.4 | 36.3 | 56.2 / +5.8 | | Pythia-1.4B (300B) | 54.5 | 63.1 | 44.5 | 28.8 | 57.1 | 71.0 | 40.5 | 92.4 | 34.6 | 54.1 | | Bloom-1.7B (366B) | 42.5 | 58.8 | 41.5 | 26.2 | 57.7 | 68.7 | 37.6 | 91.9 | 33.5 | 50.9 | | Ponder-1.4B (300B) | 59.2 | 67.5 | 49.9 | 32.4 | 60.4 | 73.5 | 44.2 | 94.3 | 37.1 | 57.6 / +3.5 | | Tinyllama-1.1B (3T) | 53.8 | 64.8 | 45.0 | 31.1 | 59.4 | 73.8 | 44.9 | 94.0 | 36.4 | 55.9 | | OPT-2.7B (300B) | 60.2 | 64.7 | 55.0 | 29.8 | 62.2 | 75.1 | 46.1 | 93.0 | 37.5 | 58.2 | | GPTneo-2.7B (300B) | 56.0 | 64.0 | 51.6 | 30.1 | 59.6 | 73.9 | 42.4 | 93.3 | 35.5 | 56.3 | | Bloom-3B (366B) | 46.2 | 63.8 | 47.1 | 31.7 | 57.8 | 70.8 | 41.4 | 93.4 | 34.6 | 54.1 | | Pythia-2.8B (300B) | 59.0 | 67.0 | 50.7 | 31.0 | 61.1 | 74.4 | 45.3 | 93.7 | 35.9 | 57.6 | | Pythia-6.9B (300B) | 62.5 | 69.6 | 54.8 | 35.6 | 62.9 | 76.6 | 48.0 | 94.6 | 36.7 | 60.1 | | Ponder-2.8B (300B) | 64.2 | 70.6 | 58.7 | 35.8 | 65.3 | 76.7 | 49.0 | 94.3 | 39.0 | 61.5 / +3.9 | | 0-shot | | | | | | | | | | | | Pythia-70M (300B) | 18.7 | 36.7 | 13.5 | 18.8 | 51.1 | 59.9 | 26.6 | 59.9 | 23.9 | 34.3 | | Ponder-70M (300B) | 33.5 | 42.5 | 24.1 | 19.1 | 51.1 | 61.5 | 28.3 | 70.3 | 27.8 | 39.8 / +5.5 | | Pythia-160M (300B) | 33.0 | 43.8 | 21.4 | 18.9 | 52.0 | 62.2 | 28.4 | 73.7 | 27.9 | 40.1 | | OPT-125M (300B) | 37.9 | 43.5 | 29.0 | 19.0 | 50.3 | 62.8 | 29.2 | 75.2 | 30.1 | 41.9 | | GPTneo-125M (300B) | 37.5 | 43.9 | 26.0 | 19.1 | 50.4 | 63.0 | 28.7 | 76.5 | 27.5 | 41.4 | | Ponder-160M (300B) | 44.3 | 46.8 | 33.8 | 20.5 | 52.3 | 63.9 | 31.9 | 76.8 | 29.6 | 44.4 / +4.3 | | Pythia-410M (300B) | 51.4 | 52.2 | 36.4 | 21.4 | 53.8 | 66.9 | 33.7 | 81.5 | 30.9 | 47.6 | | OPT-350M (300B) | 45.2 | 44.0 | 35.8 | 20.7 | 52.3 | 64.5 | 32.0 | 74.9 | 29.8 | 44.4 | | Bloom-560M (366B) | 34.3 | 47.5 | 33.3 | 22.4 | 51.5 | 63.8 | 31.5 | 80.3 | 30.5 | 43.9 | | Ponder-410M (300B) | 56.9 | 51.9 | 45.3 | 22.6 | 56.0 | 68.7 | 37.0 | 81.4 | 33.8 | 50.4 / +2.8 | | Pythia-1B (300B) | 55.9 | 56.8 | 42.0 | 24.2 | 52.5 | 70.5 | 37.7 | 83.3 | 32.7 | 50.6 | | OPT-1.3B (300B) | 57.9 | 57.1 | 52.5 | 23.4 | 59.7 | 71.8 | 41.6 | 84.3 | 34.3 | 53.6 | | GPTneo-1.3B (300B) | 57.1 | 56.2 | 45.3 | 23.2 | 55.0 | 71.2 | 38.6 | 86.1 | 34.5 | 51.9 | | Bloom-1.1B (366B) | 42.6 | 51.5 | 42.9 | 23.6 | 54.9 | 67.3 | 34.5 | 83.6 | 32.6 | 48.2 | | Ponder-1B (300B) | 62.3 | 60.5 | 51.9 | 27.0 | 56.5 | 72.2 | 41.8 | 87.4 | 35.4 | 55.0 / +4.4 | | Pythia-1.4B (300B) | 61.6 | 60.4 | 49.7 | 25.9 | 57.5 | 70.8 | 40.4 | 86.4 | 34.1 | 54.1 | | Bloom-1.7B (366B) | 46.2 | 56.4 | 44.5 | 23.7 | 56.8 | 68.5 | 37.5 | 85.0 | 33.2 | 50.2 | | Ponder-1.4B (300B) | 65.2 | 62.0 | 53.8 | 27.0 | 60.1 | 72.6 | 44.0 | 89.0 | 35.2 | 56.5 / +2.4 | | Tinyllama-1.1B (3T) | 58.8 | 60.3 | 49.3 | 28.0 | 59.0 | 73.3 | 45.0 | 88.9 | 36.4 | 55.4 | | OPT-2.7B (300B) | 63.5 | 60.8 | 56.0 | 26.8 | 61.2 | 73.8 | 45.9 | 85.8 | 36.2 | 56.7 | | GPTneo-2.7B (300B) | 62.1 | 61.2 | 51.6 | 27.5 | 57.8 | 72.3 | 42.7 | 89.3 | 35.1 | 55.5 | | Bloom-3B (366B) | 51.7 | 59.4 | 50.9 | 28.0 | 58.7 | 70.8 | 41.4 | 88.8 | 35.2 | 53.9 | | Pythia-2.8B (300B) | 64.6 | 64.4 | 54.3 | 29.5 | 60.2 | 73.8 | 45.4 | 88.5 | 34.9 | 57.3 | | Pythia-6.9B (300B) | 67.2 | 67.3 | 55.9 | 31.4 | 61.0 | 75.2 | 48.1 | 89.3 | 36.9 | 59.1 | | Ponder-2.8B (300B) | 68.9 | 66.5 | 60.8 | 32.5 | 63.6 | 75.0 | 48.6 | 91.0 | 36.5 | 60.4 / +3.1 | 3.3.2 Instruction-following Ability Evaluation To assess the instruction-following capability of our model, we further fine-tuned PonderingPythia-1B and 1.4B, as well as the corresponding official Pythia models, on the Alpaca dataset using the same settings (Taori et al., 2023). The fine-tuned models were evaluated with MT-Bench (Zheng et al., 2023), a popular multi-turn question benchmark. The experimental results are shown in Figure 4. As illustrated, both PonderingPythia-1B and 1.4B consistently outperform their official Pythia counterparts across all subtasks, achieving average improvements of 0.33 and 0.55, respectively. The marginal gains on Coding and Math tasks may be attributed to the limited coding and mathematical abilities of the Pythia models. <details> <summary>x8.png Details</summary>  ### Visual Description ## Line Chart: Loss vs. Pondering Steps ### Overview The image is a line chart showing the relationship between "Loss" and "Pondering Steps (0 = Baseline)". The chart displays a decreasing trend in loss as the number of pondering steps increases. ### Components/Axes * **X-axis:** "Pondering Steps (0 = Baseline)". The axis is marked with values 0, 1, 3, 5, and 10. * **Y-axis:** "Loss". The axis is marked with values 2.58, 2.60, 2.62, 2.64, 2.66, 2.68, 2.70, and 2.72. * **Data Series:** A single data series represented by a green line with circular markers at each data point. ### Detailed Analysis The green line represents the loss at different pondering steps. The line slopes downward, indicating a decrease in loss as the number of pondering steps increases. * **Pondering Steps = 0 (Baseline):** Loss ≈ 2.715 * **Pondering Steps = 1:** Loss ≈ 2.68 * **Pondering Steps = 3:** Loss ≈ 2.633 * **Pondering Steps = 5:** Loss ≈ 2.613 * **Pondering Steps = 10:** Loss ≈ 2.593 ### Key Observations * The loss decreases sharply from 0 to 3 pondering steps. * The rate of decrease in loss slows down after 3 pondering steps. * The lowest loss is observed at 10 pondering steps. ### Interpretation The chart suggests that increasing the number of pondering steps reduces the loss. However, the marginal benefit of adding more pondering steps diminishes as the number of steps increases. The most significant reduction in loss occurs within the first few pondering steps. The model benefits from pondering, but there are diminishing returns. </details> Figure 5: Increasing the number of pondering steps consistently reduces loss on the Pile validation set. 3.4 Impact of Pondering Steps To further investigate the effect of pondering steps on model performance, we trained several 160M-parameter Pythia models from scratch with different numbers of pondering steps: 0 (baseline), 1, 3, 5, and 10. These models were pretrained on a 30B-token subset of the Pile dataset. The results, presented in Figure 5, clearly show that increasing the number of pondering steps consistently reduces the language modeling loss on the Pile validation set. This demonstrates the significant potential and scalability of our method, suggesting that model performance can be further improved by increasing the depth of pondering steps. 4 Limitations and Future Work 4.1 Limitations There are two limitations to our work. Firstly, due to computational constraints, we only scaled our method up to a 2.8B-parameter model trained on 300B tokens from the Pile dataset. It would be interesting to extend our approach to larger models and larger-scale datasets in the future. Secondly, although our results demonstrate that the proposed method scales better than vanilla models under the same training FLOPs (Figure 3), it also introduces additional inference overhead (increasing roughly linearly with the number of pondering steps), similar to test-time scaling methods. 4.2 Future Work There are several promising directions for future work. Firstly, our proposed method is not limited to decoder-only architectures or language modeling; it has the potential to be applied to a wide range of model types and domains. For example, it could be adapted to state-space models such as Mamba (Gu & Dao, 2023), encoder models, or RWKV (Peng et al., 2023), as well as extended to other areas. Another promising direction is the introduction of token-adaptive pondering, which may significantly reduce computation and further enhance our method. It would also be interesting to investigate the interpretability of the pondering process, such as how the model "thinks" during pondering, the semantics of the pondering embedding, and whether the model learns to reflect on its predictions through pondering. Finally, exploring the combination of our method with orthogonal approaches such as CoT and other test-time scaling methods could also be an interesting direction. 5 Related Work 5.1 Test-Time Compute Scaling Scaling test-time computation has emerged as an influential approach, providing an effective alternative to merely increasing model parameters (Snell et al., 2024). Current methods for enhancing test-time computation primarily fall into two categories: parallel scaling and sequential scaling (Zeng et al., 2024; Muennighoff et al., 2025). Parallel scaling methods involve generating multiple candidate solutions simultaneously and selecting the best solution based on certain evaluation criteria. Prominent examples of this paradigm include Best-of-N search (Cobbe et al., 2021; Sun et al., 2024; Gui et al., 2024; Amini et al., 2024; Sessa et al., 2024) and Majority Vote (Wang et al., 2022). The primary difference among these parallel approaches lies in their strategy for selecting the optimal outcome. Nevertheless, parallel scaling approaches often encounter difficulty accurately identifying the best candidate solution among multiple generated possibilities (Stroebl et al., 2024; Hassid et al., 2024). Sequential scaling methods, conversely, focus on progressively refining the model’s reasoning through multiple iterative steps. Representative methods include CoT (Wei et al., 2022; Nye et al., 2021), iterative rethinking and revision (Huang et al., 2022; Min et al., 2024; Madaan et al., 2024; Wang et al., 2024b, b; Lee et al., 2025; Hou et al., 2025; Muennighoff et al., 2025; Li et al., 2025). Following the emergence of powerful OpenAI o1 and DeepSeek R1, leveraging extensive chain-of-thought prompting to scale test-time computation has become increasingly popular. Nonetheless, existing methods often come with limitations, including reliance on specially curated datasets (Allen-Zhu & Li, 2023), extended context windows (Zhu et al., 2025), and complex reinforcement learning strategies (Pang et al., 2025). In contrast, our method effectively circumvents these limitations. 5.2 Latent Thinking in Language Models Latent thinking in LMs typically refers to the hidden computational processes within transformer architectures (Yang et al., 2024; Biran et al., 2024). Prior works exploring latent thinking can generally be divided into two categories based on their implementation methods: Adding Additional Tokens: Wang et al. (2024a) proposed predicting a planning token as a discrete latent variable prior to generating reasoning steps. Similarly, Pfau et al. (2024) investigated filler tokens (e.g., “…”) and found them effective for parallelizable problems, although they also highlighted limitations compared to CoT methods, potentially constraining scalability to more complex reasoning tasks. Zhou et al. (2024) pretrained models by randomly inserting a learnable token into the training corpus, demonstrating improvements across various tasks. Furthermore, Quiet-STaR employs reinforcement learning to train models to generate intermediate rationales at each token, thereby enhancing reasoning capabilities (Zelikman et al., 2024). Reusing Hidden States: Early Universal Transformers (Csordás et al., ) reused hidden states through a transition network, aiming to enhance the encoder-decoder transformer architecture toward Turing completeness. A more recent method (Geiping et al., 2025) iterates over multiple layers of a language model to refine intermediate hidden states, treating this process as a form of latent thinking. Giannou et al. (2023) proposed looped transformer, recycling output hidden states back into input embeddings for algorithmic tasks. Similarly, Hao et al. (2024) fine-tuned models to reason directly within continuous latent spaces, using final hidden states as embeddings to achieve reasoning without explicit CoT. In contrast, our method relies on pondering embeddings derived from the predicted probabilities of LMs. 6 Conclusion In this paper, we introduce the pondering process into language models through solely self-supervised learning. Pondering LM can be naturally learned through pretraining on large-scale general corpora. Our extensive experiments across three widely adopted architectures—GPT-2, Pythia, and LLaMA—highlight the effectiveness and generality of our proposed method. 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