We employ spatial words to express both positive and negative emotions.
To test this link between vertical space and emotion, Casasanto and Dijkstra conducted an experiment, in which they asked students to move glass marbles upward or downward into one of two cardboard boxes, with both hands simultaneously, timed by a metronome.
Meanwhile, they had to recount autobiographical memories with either positive or negative emotional valence, like 'Tell me about a time when you felt proud of yourself', or 'a time when you felt ashamed of yourself".
When prompted to tell positive memories, participants began recounting their experiences faster during upward movements, but when prompted to tell negative memories they responded faster during downward movements.
Memory retrieval was most efficient when participants' motions matched the spatial directions that metaphors in language associate with positive and negative emotions.
In another experiment, the researchers tested whether these seemingly meaningless motor actions could influence the content of people's memories.
Participants were given neutral-valence prompts, like 'Tell me about something that happened during high school', so they could choose to retell something happy or sad.
Their choices were determined, in part, by the direction in which they were assigned to move marbles.
Moving marbles upward encouraged students to recount positive high school experiences like 'winning an award', but moving them downward to recall negative experiences like 'failing a test'.
"These data suggest that spatial metaphors for emotion aren't just in language. Linguistic metaphors correspond to mental metaphors, and activating the mental metaphor 'good is up' can cause us to think happier thoughts," said Casasanto.
He added: "It would be great if this basic research can help people think more positively in the world beyond the laboratory - marble therapy?"