Abstract
The ability to control impulsive actions is an important executive function that is central to the self-regulation of behaviours and, in humans, can have important implications for mental and physical health. One key factor that promotes individual differences in inhibitory control (IC) is the predictability of environmental information experienced during development (i.e. reliability of resources and social trust). However, environmental predictability can also influence motivational and other cognitive abilities, which may therefore confound interpretations of the mechanisms underlying IC. We investigated the role of environmental predictability, food motivation and cognition on IC. We reared pheasant chicks, Phasianus colchicus, under standardised conditions, in which birds experienced environments that differed in their spatial predictability. We systematically manipulated spatial predictability during their first 8 weeks of life, by either moving partitions daily to random locations (unpredictable environment) or leaving them in fixed locations (predictable environment). We assessed motivation by presenting pheasants with two different foraging tasks that measured their dietary breadth and persistence to acquire inaccessible food rewards, as well as recording their latencies to acquire a freely available baseline worm positioned adjacent to each test apparatus, their body condition (mass/tarsus3) and sex. We assessed cognitive performance by presenting each bird with an 80-trial binary colour discrimination task. IC was assessed using a transparent detour apparatus, which required subjects to inhibit prepotent attempts to directly acquire a visible reward through the barrier and instead detour around a barrier. We found greater capacities for IC in pheasants that were reared in spatially unpredictable environments compared to those reared in predictable environments. While IC was unrelated to individual differences in cognitive performance on the colour discrimination task or motivational measures, we found that environmental predictability had differential effects on sex. Males reared in an unpredictable environment, and all females regardless of their rearing environment, were less persistent than males reared in a predictable environment. Our findings, therefore, suggest that an individual’s developmental experience can influence their performance on IC tasks.
Highlights
Executive functions regulate an individual’s thoughts, actions and behaviours (Miyake and Friedman 2012)
Motivational or environmental measures best predict inhibitory control (IC) performance? Environmental treatment was the best predictor of IC performance, with birds reared in the unpredictable environment making fewer pecks, and showing greater IC, than birds reared in the predictable environment (Tables 1 and 2)
We found no evidence to suggest that IC capacities were driven by differences in our measures of general learning ability, motivation, IC task or sex (Tables 1 and 2)
Summary
Executive functions regulate an individual’s thoughts, actions and behaviours (Miyake and Friedman 2012). One behavioural assay of IC that is common to both human and non-human animals is the suppression of motor actions, which can be assayed using a detour task (Diamond 1990; Kabadayi et al 2018; MacLean et al 2014) This task requires subjects to inhibit attempts to acquire a clearly visible, but inaccessible food reward that is positioned behind a transparent barrier and instead move away from the visible reward and detour around the obstacle to access the food (i.e. response inhibition; Nigg 2017). Individual performance on IC tasks is predicted by non-cognitive traits such as high food motivation (van Horik et al 2018a), low body condition (Shaw 2017), high arousal (Bray et al 2015), environmental enrichment (Clarke et al 1951), fearfulness (Regolin et al 1995) and prior experience with transparent objects (van Horik et al 2018a). We tested whether, between individuals, any of these potential cognitive and non-cognitive factors provided a better explanation of differences in IC
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