Touch can produce detailed, permanent memories

Detailed, durable, long-term memory representations are stored as a natural product of haptic perception.

Touch can produce detailed, permanent memories
Image: Association for Psychological Science

Humans can perceive the shape of objects by touch alone, by extracting geometric features such as edges. The sense of touch differs from the other senses because of two fundamental features of its receptor surface, the skin.

According to a new study, exploring objects through touch can create detailed, durable memories for those items, notwithstanding when we don’t plan to retain the object’s details.

Fabian Hutmacher of the University of Regensburg said. “An especially interesting finding was that participants were able to visually identify an object they had never seen but only touched one week before without the intention of memorization. This is even more remarkable as the competing objects in the recognition test belonged to the same basic-level category – that is, the previously presented object was only identifiable based on subtle touch-based details but not on much more salient visual details.”

“The study challenges existing cognitive and neural models of memory storage and retrieval, as these models seem to be unable to account for a large amount of stored information.”

During the experiment, participants were asked to wear a blindfold to explore everyday objects. Scientists told the members they would be tried on the items later, so they should give careful consideration to the surface, shape, and weight of each object.

The members, still blindfolded, finished a haptic memory test for half of the items quickly after exploring them. They held each object they had investigated and a comparative novel protest that was recognizable just by unobtrusive points of interest – their task was to show which object they had explored previously. They finished a similar test with the other half of the items one week later.

Participants showed almost perfect recall on the test that followed the exploration period, correctly identifying the object they had explored 94% of the time. Remarkably, participants still showed robust memory for the original objects 1 week later, with 84% accuracy.

In a second experiment, a new group of participants explored the same 168 objects without knowing they would be tested on them. This time, scientists asked the participants to rate the pleasantness of each object based on texture, shape, and weight.

Participants returned one week later for an unexpected memory test, finishing a blindfolded touch-based recognition task for half of the articles. For whatever is left of the articles, they finished a visual recognition task, in which they saw the first object and a comparative question set on a table, and showed which one they recently investigated.

After every preliminary, the members additionally announced in the event that they addressed dependent on reviewing subtle elements of their touch-based investigation, feeling an obscure recognition, or essentially speculating.

The results showed that participants remembered the objects with high accuracy. In the blindfolded test, participants answered correctly on 79% of the trials. In the cross-modal visual test, participants identified the correct object 73% of the time.

Hutmacher said, “These results suggest that the human mind effortlessly and automatically stores detailed and durable representations of a vast amount of perceptual experiences, including haptic ones. We want to explore the idea that storing such a vast amount of information may in fact be functional as it may guide our behavior and contribute to its fine-tuning without being accompanied by conscious experience.”

The findings of the study are published in Psychological Science.