Lucy G. Cheke

The Evolution of Self-Control

Significance Although scientists have identified surprising cognitive flexibility in animals and potentially unique features of human psychology, we know less about the selective forces that favor cognitive evolution, or the proximate biological mechanisms underlying this process. We tested 36 species in two problem-solving tasks measuring self-control and evaluated the leading hypotheses regarding how and why cognition evolves. Across species, differences in absolute (not relative) brain volume best predicted performance on these tasks. Within primates, dietary breadth also predicted cognitive performance, whereas social group size did not. These results suggest that increases in absolute brain size provided the biological foundation for evolutionary increases in self-control, and implicate species differences in feeding ecology as a potential selective pressure favoring these skills. Cognition presents evolutionary research with one of its greatest challenges. Cognitive evolution has been explained at the proximate level by shifts in absolute and relative brain volume and at the ultimate level by differences in social and dietary complexity. However, no study has integrated the experimental and phylogenetic approach at the scale required to rigorously test these explanations. Instead, previous research has largely relied on various measures of brain size as proxies for cognitive abilities. We experimentally evaluated these major evolutionary explanations by quantitatively comparing the cognitive performance of 567 individuals representing 36 species on two problem-solving tasks measuring self-control. Phylogenetic analysis revealed that absolute brain volume best predicted performance across species and accounted for considerably more variance than brain volume controlling for body mass. This result corroborates recent advances in evolutionary neurobiology and illustrates the cognitive consequences of cortical reorganization through increases in brain volume. Within primates, dietary breadth but not social group size was a strong predictor of species differences in self-control. Our results implicate robust evolutionary relationships between dietary breadth, absolute brain volume, and self-control. These findings provide a significant first step toward quantifying the primate cognitive phenome and explaining the process of cognitive evolution.

Effects of the mu-opioid receptor antagonist GSK1521498 on hedonic and consummatory eating behaviour: a proof of mechanism study in binge-eating obese subjects

The opioid system is implicated in the hedonic and motivational processing of food, and in binge eating, a behaviour strongly linked to obesity. The aim of this study was to evaluate the effects of 4 weeks of treatment with the mu-opioid receptor antagonist GSK1521498 on eating behaviour in binge-eating obese subjects. Adults with body mass index ⩾30 kg m−2 and binge eating scale scores ⩾19 received 1-week single-blind placebo run-in, and were then randomized to 28 days with either 2 mg day−1 GSK1521498, 5 mg day−1 GSK1521498 or placebo (N=21 per arm) in a double-blind parallel group design. The outcome measures were body weight, fat mass, hedonic and consummatory eating behaviour during inpatient food challenges, safety and pharmacokinetics. The primary analysis was the comparison of change scores in the higher-dose treatment group versus placebo using analysis of covariance at each relevant time point. GSK1521498 (2 mg and 5 mg) was not different from placebo in its effects on weight, fat mass and binge eating scores. However, compared with placebo, GSK1521498 5 mg day−1 caused a significant reduction in hedonic responses to sweetened dairy products and reduced calorific intake, particularly of high-fat foods during ad libitum buffet meals, with some of these effects correlating with systemic exposure of GSK1521498. There were no significant effects of GSK1521498 2 mg day−1 on eating behaviour, indicating dose dependency of pharmacodynamics. GSK1521498 was generally well tolerated and no previously unidentified safety signals were detected. The potential for these findings to translate into clinically significant effects in the context of binge eating and weight regain prevention requires further investigation.

Tool-use and instrumental learning in the Eurasian jay (Garrulus glandarius)

Recent research with Rooks has demonstrated impressive tool-using abilities in captivity despite this species’ classification as a non-tool-user in the wild. Here, we explored whether another non-tool-using corvid, the Eurasian Jay, would be capable of similar feats and investigated the relative contributions of causal knowledge and instrumental conditioning to the birds’ performance on the tasks. Five jays were tested on a variety of tasks involving water displacement. Two birds reliably interacted with the apparatuses. In these tasks, both birds showed a preference for inserting stones into a tube containing liquid over a tube containing a solid or a baited ‘empty’ tube and also for inserting sinkable items over non-sinkable items into a tube of water. To investigate the contribution of instrumental conditioning, subjects were then tested on a series of tasks in which different cues were made available. It was found that, in the absence of any apparent causal cues, these birds showed a clear preference for the rewarded tube when the food incrementally approached with every stone insertion, but not when it simply “appeared” after the correct number of stone insertions. However, it was found that subjects did not prefer to insert stones into a tube rewarded by the incremental approach of food if the available causal cues violated the expectations created by existing causal knowledge (i.e. were counter-intuitive). An analysis of the proportion of correct and incorrect stone insertions made in each trial across tasks offering different types of information revealed that subjects were substantially more successful in experiments in which causal cues were available, but that rate of learning was comparable in all experiments. We suggest that these results indicate that Eurasian jays use the incremental approach of the food reward as a conditioned reinforcer allowing them to solve tasks involving raising the water level and that this learning is facilitated by the presence of causal cues.

Eurasian jays (Garrulus glandarius) overcome their current desires to anticipate two distinct future needs and plan for them appropriately

Western scrub-jays (Aphelocoma californica) have been shown to overcome present satiety to cache food they will desire in the future. Here, we show that another corvid, the Eurasian jay (Garrulus glandarius), can distinguish between two distinct future desires and plan for each appropriately, despite experiencing a conflicting current motivation. We argue that these data address the criticisms of previous work, and suggest a way in which associative learning processes and future-oriented cognition may combine to allow prospective behaviour.

Evidence suggesting that desire-state attribution may govern food sharing in Eurasian jays

State-attribution is the ability to ascribe to others an internal life like one’s own and to understand that internal, psychological states such as desire, hope, belief, and knowledge underlie others’ actions. Despite extensive research, comparative studies struggle to adequately integrate key factors of state-attribution that have been identified by evolutionary and developmental psychology as well as research on empathy. Here, we develop a behavioral paradigm to address these issues and investigate whether male Eurasian jays respond to the changing desire-state of their female partners when sharing food. We demonstrate that males feed their mates flexibly according to the female’s current food preference. Critically, we show that the males need to see what the female has previously eaten to know what food she will currently want. Consequently, the males’ sharing pattern was not simply a response to their mate’s behavior indicating her preference as to what he should share, nor was it a response to the males’ own desire-state. Our results raise the possibility that these birds may be capable of ascribing desire to their mates.

Higher body mass index is associated with episodic memory deficits in young adults

Obesity has become an international health crisis. There is accumulating evidence that excess bodyweight is associated with changes to the structure and function of the brain and with a number of cognitive deficits. In particular, research suggests that obesity is associated with hippocampal and frontal lobe dysfunction, which would be predicted to impact memory. However, evidence for such memory impairment is currently limited. We hypothesised that higher body mass index (BMI) would be associated with reduced performance on a test of episodic memory that assesses not only content, but also context and feature integration. A total of 50 participants aged 18–35 years, with BMIs ranging from 18 to 51, were tested on a novel what–where–when style episodic memory test: the “Treasure-Hunt Task”. This test requires recollection of object, location, and temporal order information within the same paradigm, as well as testing the ability to integrate these features into a single event recollection. Higher BMI was associated with significantly lower performance on the what–where–when (WWW) memory task and all individual elements: object identification, location memory, and temporal order memory. After controlling for age, sex, and years in education, the effect of BMI on the individual what, where, and when tasks remained, while the WWW dropped below significance. This finding of episodic memory deficits in obesity is of concern given the emerging evidence for a role for episodic cognition in appetite regulation.

Do different tests of episodic memory produce consistent results in human adults

A number of different philosophical, theoretical, and empirical perspectives on episodic memory have led to the development of very different tests with which to assess it. Although these tests putatively assess the same psychological capacity, they have rarely been directly compared. Here, a sample of undergraduates was tested on three different putative tests of episodic memory (What-Where-When, Unexpected Question/Source Memory, and Free Recall). It was predicted that to the extent to which these different tests are assessing the same psychological process, performance across the various tests should be positively correlated. It was found that not all tests were related and those relationships that did exist were not always linear. Instead, two tests showed a quadratic relationship, suggesting the contribution of multiple psychological processes. It is concluded that not all putative tests of episodic cognition are necessarily testing the same thing.

How Do Children Solve Aesop's Fable?

Studies on members of the crow family using the “Aesops Fable” paradigm have revealed remarkable abilities in these birds, and suggested a mechanism by which associative learning and folk physics may interact when learning new problems. In the present study, children between 4 and 10 years of age were tested on the same tasks as the birds. Overall the performance of the children between 5–7-years was similar to that of the birds, while children from 8-years were able to succeed in all tasks from the first trial. However the pattern of performance across tasks suggested that different learning mechanisms might be being employed by children than by adult birds. Specifically, it is possible that in children, unlike corvids, performance is not affected by counter-intuitive mechanism cues.

Obesity and insulin resistance are associated with reduced activity in core memory regions of the brain

ABSTRACT Increasing research in animals and humans suggests that obesity may be associated with learning and memory deficits, and in particular with reductions in episodic memory. Rodent models have implicated the hippocampus in obesity‐related memory impairments, but the neural mechanisms underlying episodic memory deficits in obese humans remain undetermined. In the present study, lean and obese human participants were scanned using fMRI while completing a What‐Where‐When episodic memory test (the “Treasure‐Hunt Task”) that assessed the ability to remember integrated item, spatial, and temporal details of previously encoded complex events. In lean participants, the Treasure‐Hunt task elicited significant activity in regions of the brain known to be important for recollecting episodic memories, such as the hippocampus, angular gyrus, and dorsolateral prefrontal cortex. Both obesity and insulin resistance were associated with significantly reduced functional activity throughout the core recollection network. These findings indicate that obesity is associated with reduced functional activity in core brain areas supporting episodic memory and that insulin resistance may be a key player in this association. HIGHLIGHTSObesity associated with reduced activity in core recollection network during episodic memory.Insulin resistance associated with reduced activity in core recollection network during episodic memory.Insulin resistance, but not obesity, associated with poorer memory performance.

The six blind men and the elephant: Are episodic memory tasks tests of different things or different tests of the same thing?

Highlights • Many different episodic memory tests were compared in the same sample of 3–6 year-old children.• Age-independent correlation was low, suggesting that these tests should not be treated as equivalent.• A single principal component best explained variance in the dataset.• These test should not be used in parallel, but should be adapted as a battery.