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Developing the knowledge of number digits in a child-like robot


Number knowledge can be boosted initially by embodied strategies such as the use of fingers. This Article explores the perceptual process of grounding number symbols in artificial agents, particularly the iCub robot—a child-like humanoid with fully functional, five-fingered hands. It studies the application of convolutional neural network models in the context of cognitive developmental robotics, where the training information is likely to be gradually acquired while operating, rather than being abundant and fully available as in many machine learning scenarios. The experimental analyses show increased efficiency of the training and similarities with studies in developmental psychology. Indeed, the proprioceptive information from the robot hands can improve accuracy in the recognition of spoken digits by supporting a quicker creation of a uniform number line. In conclusion, these findings reveal a novel way for the humanization of artificial training strategies, where the embodiment can make the robot’s learning more efficient and understandable for humans.

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Fig. 1: Schematics of the artificial neural network architecture.
Fig. 2: Accuracy rate on the test set over epochs.
Fig. 3: Accuracy rate on the test set over epochs.

Data availability

The data for the models presented in this paper can be found in the GitHub repository: A Supplementary Video of the iCub counting from 1 to 10 is also provided. The Google Tensorflow Speech Command database can be downloaded from

Code availability

The source code for the models presented in this paper can be found in the GitHub repository:


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A.D.N. acknowledges the support of the EPSRC through project grant no. EP/P030033/1 (NUMBERS). A.D.N. also acknowledges the support of the NVIDIA Corporation with the donation of the GeForce Titan X and the Tesla K40 GPUs used for this research.

Author information




A.D.N. conceptualized the experiment, developed the methodology and designed the baseline artificial neural network architecture. A.D.N. and J.L.M. collaborated on the design of the embodied model. A.D.N. implemented the source code, ran the simulations, validated the results and wrote the first draft of the article. J.L.M. provided relevant ideas from cognitive psychology and neuroscience and contributed to the discussion.

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Correspondence to Alessandro Di Nuovo.

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Di Nuovo, A., McClelland, J.L. Developing the knowledge of number digits in a child-like robot. Nat Mach Intell 1, 594–605 (2019).

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