How did experiments with monkeys demonstrate cross-modal learning between touch and vision?

In experiments with young monkeys, researchers demonstrated cross-modal learning by training the animals to discriminate between differently shaped objects—such as balls, cubes, cones, and cylinders—using only their sense of touch.1

The process involved the following steps:

• Tactile Training: Monkeys were given two objects at a time to feel with their hands without being able to see them. They were rewarded with food for selecting a specific shape (e.g., a cube) and rejecting another (e.g., a cone).1
• Visual Testing: Once the monkeys had mastered these tactile discriminations, they were presented with the same task visually, using pictures of the objects they had previously felt.1
• Outcome: The monkeys were often able to correctly discriminate the visually presented figures, despite having only learned the shapes through touch.1

This phenomenon, known as cross-modal learning, suggests a transfer effect where the animals utilized their earlier tactile experience to guide their visual perception. This illustrates how one sense can be anchored to another to facilitate the development of spatial perception.1