Parents with limited income spend less time than their advantaged counterparts engaging in educational activities with their children. A common explanation is that financial scarcity creates a “bandwidth tax” on cognition. The scarcity framework highlights two components: attentional capacity (the ability to focus amid competing demands) and executive control (the ability to resist temptation and act in line with long-term goals). No study has tested which is the primary constraint on parental investment or separated subjective financial stress from income itself. We address both gaps through the Early Investment Project, a survey of 1,932 mothers of kindergartners in Chicago Public Schools that simultaneously measures felt scarcity, household income, attentional capacity, and present bias. Our outcome captures parent-reported obstacles to fulfilling intentions to read with their child. Two main findings emerge. First, attentional capacity — not self-control — is the primary constraint: the Attention Index is associated with all four parent-side barriers at the 1% level across all models, including those with strict controls for depression, agency, and growth mindset, while present bias is essentially uncorrelated with the outcomes. Second, felt scarcity, not household income, is associated with attentional deficits: the scarcity coefficient on the Attention Index persists when income is controlled, whereas income shows no independent association with attention. Placebo tests confirm specificity. These results indicate that attention, not self-control, is the mechanism through which financial insecurity is linked to reduced parental investment, and that perceived insufficiency, rather than income, is its primary correlate.