Line Spacing & Readability

Reading comprehension is a foundational cognitive process. As we move from paper to screens, design decisions play a critical role in shaping outcomes. Line spacing, or "leading," impacts visual density, which in turn affects perceptual fluency and navigation during reading tasks. This study was completed via the Human-Centered Design & Engineering M.S. at the University of Washington.

Collaborative Researcher

Quantitative

Survey Data Analysis

Between-subject Study

Context & Problem

Research Question

My role

Collaborative Researcher

Research Approach

Prep

Research Qeestion: Does line spacing affect reading comprehension?

Survey Development

Between-subjects online experiment conducted on Qualtrics.

Samples were balanced to 2 conditions (1.0 Spacing or 2.0 Spacing)

Fielding
‍

We fileded 98 usable responses.

Participants ages ranged from 18 to 65 among a variety of demographics (age, gender, race).

Analysis
‍

Independent Sample T-Test

Mediation Analysis (Objective measures): Reading time, Quiz scores

Mediation Analysis (Subjective Measures): Composite Readability index (Cronbach's α = .93)

Key Findings

Finding 01

Comprehension

Double-spaced group scored higher
(M=3.95 vs 3.20) Missed significance (p=.057, Cohen's d=.67)

Finding 02

Readability

No significant difference in subjective readability between conditions

Finding 03

Manipulation check

Participants couldn't reliably distinguish spacing conditions

Impact

Null results are meaningful as spacing alone isn't the driver of comprehension

The near-significant comprehension effect (p=.057) suggests a trend worth exploring with a larger sample

We found that line spacing (whether 1.0 or 2.0) had no significant effect on reading comprehension across digital surfaces. While this contradicts our initial hypothesis, it carries a practical implication: when designing text-heavy digital experiences, tighter spacing can be used freely without sacrificing understanding, making it a viable tool for conserving screen real estate.

Reflection

This study was conducted as part of a course project, which afforded a level of ownership rarely available in a corporate setting. With no stakeholder constraints or approval processes, decisions could be made efficiently and with full autonomy, a valuable contrast to agency or in-house research environments.The absence of a budget introduced its own set of challenges. Without participant incentives, recruitment relied on university networks and peer data-sourcing groups. Despite these limitations, the study reached a sample size of 98, a meaningful outcome given the resource constraints.The findings open the door for further exploration. While line spacing did not emerge as a statistically significant predictor of reading comprehension, the effect approached significance, suggesting that a larger sample size could yield more conclusive results. Replication with greater statistical power would be a worthwhile next step.