An information processing system comprising: an input apparatus including at least one strain sensor; a motion sensor (114, 115); and an information processing apparatus, wherein the input apparatus is at least partially elastically deformable in response to an external force applied thereto, the strain sensor provides an output corresponding to deformation of the input apparatus, the motion sensor provides an output corresponding to a motion and/or orientation of the input apparatus; and wherein the information processing apparatus includes a data obtaining section (81, S302, S402) that obtains strain data corresponding to the output of the strain sensor and motion data corresponding to the output of the motion sensor, and a game processing section (81, S307, S410) that executes in response to moving the input apparatus while deforming it a game process based on the motion data while the deformation of the input apparatus is detected based on the strain data, characterized in that the game processing section executes the game process based on the motion data when the strain data indicates that the extent to which deformation occurs of the input apparatus is greater than a first threshold, and executes the game process based on the motion data even when the strain data does not indicate that the extent to which deformation occurs of the input apparatus is greater than the first threshold, if the strain data indicates that the extent to which deformation occurs of the input apparatus is not smaller than a second threshold smaller than the first threshold after the extent to which deformation occurs of the input apparatus has been greater than the first threshold, the thresholds being configured such that the game process can continue even when the input apparatus recovers its original shape to some extent after an operation of deforming the input apparatus. the input apparatus is at least partially elastically deformable in response to an external force applied thereto, the strain sensor provides an output corresponding to deformation of the input apparatus, the motion sensor provides an output corresponding to a motion and/or orientation of the input apparatus; and wherein the information processing apparatus includes a data obtaining section (81, S302, S402) that obtains strain data corresponding to the output of the strain sensor and motion data corresponding to the output of the motion sensor, and a game processing section (81, S307, S410) that executes in response to moving the input apparatus while deforming it a game process based on the motion data while the deformation of the input apparatus is detected based on the strain data, characterized in that the game processing section executes the game process based on the motion data when the strain data indicates that the extent to which deformation occurs of the input apparatus is greater than a first threshold, and executes the game process based on the motion data even when the strain data does not indicate that the extent to which deformation occurs of the input apparatus is greater than the first threshold, if the strain data indicates that the extent to which deformation occurs of the input apparatus is not smaller than a second threshold smaller than the first threshold after the extent to which deformation occurs of the input apparatus has been greater than the first threshold, a data obtaining section (81, S302, S402) that obtains strain data corresponding to the output of the strain sensor and motion data corresponding to the output of the motion sensor, and a game processing section (81, S307, S410) that executes in response to moving the input apparatus while deforming it a game process based on the motion data while the deformation of the input apparatus is detected based on the strain data, characterized in that the game processing section executes the game process based on the motion data when the strain data indicates that the extent to which deformation occurs of the input apparatus is greater than a first threshold, and executes the game process based on the motion data even when the strain data does not indicate that the extent to which deformation occurs of the input apparatus is greater than the first threshold, if the strain data indicates that the extent to which deformation occurs of the input apparatus is not smaller than a second threshold smaller than the first threshold after the extent to which deformation occurs of the input apparatus has been greater than the first threshold, the thresholds being configured such that the game process can continue even when the input apparatus recovers its original shape to some extent after an operation of deforming the input apparatus.