Children anticipate past events to the left and future events to the right: Evidence from eye movements and time-space compatibility effects

Typically, people in cultures with a left-to-right reading direction mentally link past-related stimuli with the left space and future-related stimuli with the right space ("mental timeline”; MTL). Hence, enhanced reading experience might play a fundamental role in the development of the MTL. To test this, we implemented a child-friendly time-space compatibility design. Children from different grades of elementary school saw a picture (e.g., a half-peeled orange) together with the word “earlier” or the word “later”. This design allowed us to assess whether the MTL biases anticipatory eye movements in response to word processing. Thereafter, two horizontally arranged pictures appeared either compatible with the MTL (e.g., an unpeeled orange on the left side and a completely peeled orange on the right side) or in a reversed, i.e. incompatible mapping. Participants responded with their right or left hand to indicate which picture matched the previously heard auditory prompt. In Study 1, we tested children (first to fourth grade) and adults. Anticipatory looks elicited by auditory prompts and response times reflected MTL effects with no differences between age groups. In Study 2, we contrasted two larger groups of first and fourth graders. We replicated MTL effects for anticipatory looks, but not for response times. Anticipatory looks were stronger biased by the MTL in fourth compared to first graders. We conclude that studying MTL effects in children is restricted by task difficulty. If MTL effects appear, they are not strongly modulated by formal education. Thus, basic MTL effects might be acquired before elementary school.