SES ranges

Lately, I’ve been thinking more about SES (socioeconomic status) ranges for participants in cognitive and developmental psychology research. I’d like to know more about SES-based differences in language and cognitive development, but I’ve only begun to scratch the surface with a literature review in this regard. In the long-term, I’d really like to do a review paper on this topic.

It seems likely that we usually draw upon “convenience samples.” These are families who live near a major research institution, and who have time to volunteer. Working at Harvard, I found it difficult to get a normal distribution on a number of standardized assessments of verbal and nonverbal abilities (e.g., MCDI, PPVT, CELF, TROG, KBIT). This raises the important question as to whether our results are generalizable to a broader population. Moreover, small samples from low-SES populations might make it a bit difficult to interpret SES effects.

For example, I was reading this article this morning that described large SES effects:

“Toddlers came from a range of socioeconomic backgrounds, as indexed by mother’s education level gathered by parent report. Participants’ mothers’ educational attainment fell into the following ordered categories: 1) less than high school degree (n = 1), 2) high school diploma (10), 3) some college (8), 4) college degree (16), and 5) advanced degree (41). One parent declined to provide this information.” (Bergelson & Swingley, 2013).

Here’s what that range looks like:


The authors found: “Mother’s education has a significant and graded effect on toddlers’ overall word-comprehension performance. These effects were large, as Figure 4 shows.” However, discussing why these effects exist is outside the scope of this particular paper: “Our data do not speak to the origins of performance differences correlated with socioeconomic status; based on the work of previous authors, differences in the children’s language environment are plausible causes.”

These effects were indeed very large, and the pattern is strikingly clear, but I do wonder what would happen if more children from low-SES groups were included in the sample. In this study, 75% of the mothers had a college degree or a graduate-level degree. More research is surely needed to better understand SES effects and their origins.

For now, back to literature review!


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