Skip to main content

The effects of early-life adversity on cognition: A comparative approach.

Periodic Reporting for period 3 - COMSTAR (The effects of early-life adversity on cognition: A comparative approach.)

Reporting period: 2018-10-01 to 2020-03-31

This research programme investigates how adversity experienced early in life affects cognition in adulthood in two different long-lived species, humans and European starlings. Previous research has suggested that there might be cross-species similarities in the way early-life adversity shapes cognition, but the extent of commonalities has not been systematically investigated. We are focussing on three cognitive domains where we have some evidence that early-life adversity may be important: impulsivity, dietary cognition, and threat-related cognition. For each domain, we seek to characterise how the outcome relates to different facets of early-life adversity. Early-life adversity will be measured using socioeconomic and familial variables in humans, but in young starlings it will be experimentally manipulated via cross-fostering and hand-rearing siblings apart
so that they experience different early histories. To measure the adult outcomes in each cognitive domain, we are developing novel behavioural paradigms with directly analogous versions in the two species. We are also examining whether telomere
length, a cellular measure of cumulative stress exposure, statistically mediates the relationships between early-life adversity and the cognitive outcomes, thus testing recent theoretical models based on psychological adaptation to ones own physical state. As well as describing associations between early-life adversity and adult outcomes, we will focus on adaptive questions: do the observed effects of early-life adversity simply represent pathology, or can they be considered as adaptive responses? Thus, we will move beyond cataloguing the cognitive consequences of early-life
adversity, and begin to explain them.

These issues are important for society, as it is clear that some of the variation in adult health, behaviour and well-being has its origins in childhood experience. It is therefore an important priority to understand how and why childhood experience shapes adult decision-making. We aim to go beyond simply labelling the decision-making of people who have suffered early adversity as 'faulty', and instead try to understand the specific ways that individuals shift their priorities in response to the early lives they have had. This could ultimately inform between interventions and institutions for young people. By focusing on a non-human species where we have experimental control of early experience, we hope to be able to move beyond the mass of correlations that tends to exist in human life-course data.
To date, we have reared a cohort of starlings where each of four siblings experienced a different regime in the formative early weeks of life. Roughly, one sibling had enough to eat but had to beg to get it; one did not have to beg so much but got scarcely enough food; one did not have to beg and receive ample food; and one had to beg and received scarcely enough. All the birds are adults now and there is obvious difference between them. However, we are conducting sublte behavioural tests on their motivation for food, their responses to threats, and their preferences for immediate versus delayed reward. It seems that there are some key behavioural differences. Generally, these are more complex than being able to say 'those with more early adversity are more obese or more anxious overall'. Rather, it seems that specific components of early experience influence different components of the adult psychology, for example the motivation to work for food and the amount of it that an individual consumes. To support this bird work, we have developed an automated system (the social foraging sysyem) which allows us to measure the birds' foraging and decision-making as they fly freely about their aviaries.

In parallel to this bird work, we are performing a series of studies on human volunteers where we relate aspects of their childhood (retrosepctively recalled) to their performance on a suite of cognitive tasks. In many cases we are specially developing tasks and measures inspired by what we have been able to do with the birds. We have been exploring the hypothesis that insecurity and stress - both in childhood but also in adulthood - are related to food motivation, eating behaviour and obesity. We have established such connections from the previous literature, and we are currently conducting original studies of our own.
Ther have been many studies showing that people who had childhood adversity or trauma have different adult outcomes (usually, poorer health). However, these studies so far are quite non-specific in that they compare childhood adversity in general to some global outcomes. We are trying to go beyond this by teasing out exactly which components of childhood experience influence aspects of adult psychology. We also aim to go beyond the 'deficit model' typical of this literature, which sees people who experienced early-life adversity as solely having deficits relative to luckier people. Instead, we want to reconceptualise the problem as people having in some cases different but equally functional strategies for dealing with adult life, according to the inputs that their lives have given them. We hope to apply our results to understanding how social inequalities - in health, in behaviour - originate in early life and can become entrenched over the life-course.