Counting Is Easier while Experiencing a Congruent Motion (Extract: Materials and Method)

Participants

Fifty-six students of the University of Bologna (30 females, mean age: 22 years) took part in the experiment and received 5 euro for their participation. The majority of participants had a background in humanities and they were all naïve as to the purpose of the experiment. Eight participants were eliminated and replaced from the same pool since they made more than 4 calculation errors (corresponding to the participants' errors mean plus one standard deviation).

Apparatus and stimuli

Participants were asked to keep adding or subtracting 3 to a starting number (e.g., 371) for 22 seconds and to say the result of each calculation aloud (e.g., 374, 377, 380 or 368, 365, 362 and so on, for additions and subtractions, respectively, until the 22 seconds were elapsed). We made sure that the starting numbers: a) were always composed by three digits (e.g., 371; 587); b) started with two different digits (i.e,, 3 or 5, such as 371 or 588).

Procedure

Participants were required to make the calculations (additions or subtractions) while (on-line condition) or after (off-line condition) taking the elevator (passive mode) or taking the stairs (active mode). In other words, half of the participants were asked to make the calculations while taking the elevator and the stairs (on-line condition), whereas the other half had to make additions and subtractions after the elevator or the stairs were taken (off-line condition).

In order to keep the active and passive motion modes separated, each condition included two blocks (whose order was counterbalanced between subjects): in one block participants performed the calculations while taking the elevator or just after it had been taken, whereas in the other block calculations were performed while taking the stairs or just after they had been taken. Within each block, participants were required to perform four trials, resulting from the combination of the two types of calculation (i.e., additions and subtractions) and the two types of motion (i.e., ascending and descending). We designed each block in order to make additions and subtractions always alternate (i.e., an addition always followed a subtraction and vice versa).

At the beginning (for on-line condition) or at the end (for off-line condition) of the motion, the experimenter spoke the starting number aloud and a go signal followed. Immediately after the go signal, the participant had to repeat the starting number and then to keep speaking aloud the result of each calculation for 22 seconds consecutively until a stop signal was given. Therefore, the number of calculations made within the 22 seconds window entirely depended on the participants' calculation speed. If participant made a calculation error, the trial was stopped and a new trial started over choosing a different starting number. No feedback of any kind was given during the calculations. Instructions stressed the importance of accuracy over speed.

The experimenter was always present during the whole experiment. For the passive mode, the experimenter went up/down using the elevator together with the participant. For the active mode, she walked close to the participant while going up/down the stairs and asked the participant to keep her pace throughout the whole movement. In other words, the participant and the experimenter went up/down the stairs together.

Responses were recorded by the experimenter who kept track and note of the starting number assigned to the participants and of the final number reached at the end of the 22 sec time window.

Participants were thanked and debriefed at the end of the experiment.