The presence of the reverse distance effect depends on the familiarity of the sequences being processed.

Number order processing is thought to be characterised by a reverse distance effect whereby consecutive sequences (e.g., 1-2-3) are processed faster than non-consecutive sequences (e.g., 1-3-5). However, there is accumulating evidence that the reverse distance effect is not consistently observed. In this context, the present study investigated whether the presence of the reverse distance effect depends on the familiarity of the sequences being processed. Supporting this proposal, Experiment 1 found that the reverse distance effect was only present when the presented consecutive sequences were considerably more familiar than the presented non-consecutive sequences. Additionally, the sequence 1-2-3 has been suggested to play a pivotal role in the presence of the reverse distance effect due to being both the most familiar and fastest processed sequence. However, it is contested whether 1-2-3 is processed fast because it is familiar or simply because it can typically be verified as ordered from only its first two digits. Supporting the familiarity explanation, Experiments 2 and 3 found that 1-2-3 was processed characteristically fast regardless of whether it could be verified from its first two digits. Taken together, these findings suggest that sequence familiarity plays a critical role in the presence or absence of the reverse distance effect.