# The different effects of aspect ratios of letters on the letter-row tilt illusion in staircase and non-staircase stimuli

## TL;DR

This study explores how the shape of letters affects the perception of tilt in horizontal rows, with and without staircase-like structures.

## Contribution

The study reveals distinct mechanisms behind the letter-row tilt illusion depending on the presence of staircase structures and letter aspect ratios.

## Key findings

- The letter-row tilt illusion occurs in both staircase and non-staircase letter-rows.
- The illusion increases with longer horizontal line segments in staircase structures.
- Aspect ratios affect the illusion differently in staircase and non-staircase structures.

## Abstract

The letter-row tilt illusion is the illusion that the row is perceived to be tilted, when a set of letters is repeated in a physically horizontal or vertical row. We quantitatively examined the effects of aspect ratios of letters on the letter-row tilt illusion in horizontal letter-rows with or without a staircase structure of horizontal line segments. In Experiment 1, the results quantitatively showed that the illusion significantly occurred in letter-rows with and without the staircase structure. In Experiment 2, the results showed that the amount of illusion in letter-rows with the staircase structure increased as relative and absolute lengths of the horizontal line segments increased. In Experiment 3, the results showed that the amount of illusion in letter-rows without the staircase structure had different tendencies in aspect ratios from that with the staircase structure. The present study suggested that different mechanisms were responsible for the letter-row tilt illusions with and without the staircase structure.