Cross-Modal Object Recognition and Reliability Between Visual and Tactile Senses in Octopus (Callistoctopus aspilosomatis).

Octopuses have well-developed sensory organs and a large brain, which allows them to use multiple senses, such as vision, touch, and taste. Most studies on the sensory abilities of octopuses have focused on a single sensory modality, particularly vision. However, octopuses are simultaneously exposed to multiple sensory stimuli. If an octopus can transfer information about its environment between two different senses, then the flexibility of its multisensory system must provide an adaptive advantage. This type of recognition system is referred to as cross-modal recognition. Here, we describe cross-modal recognition between the vision and touch of novel objects in octopuses. Octopuses were engaged in learning three geometrically identical objects that provided different sensory information: i) a soft object transforming against touch (visual-only condition), ii) a hard object being shielded (tactile-only condition), and iii) a hard object (visuo-tactile condition). In the shape discrimination test of objects (ball vs. cross), all octopuses, except those in the visual-only condition, selected the correct object. Furthermore, octopuses that first learned about an object by touch immediately recognized it solely through vision. These observations indicate that octopuses are more likely to depend on the tactile information of objects in the process of forming representations of novel objects, and that cross-modal object recognition across tactile and visual perception exists in octopuses.