According to Ackerman, these effects happen because our understanding of abstract concepts is deeply rooted in physical experiences. Touch is the first of our senses to develop. In the earliest days of our lives, our ability to feel things like texture and temperature provides a tangible framework that we can use to understand more nebulous notions like importance or personal warmth. Eventually, the two become tied together, so that touching objects can activate the concepts that they are associated with.
This idea is known as "embodied cognition" and the metaphors and idioms in our languages provide hints about such associations. The link between weight and importance comes through in phrases such as "heavy matters" and the "gravity of the situation". We show the link between texture and harshness when we describe a "rough day" or "coarse language". And the link between hardness and stability or rigidity becomes clear when we describe someone as "hard-hearted" or "being a rock".