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Neuropsychological mechanisms of interval timing behaviour. BioEssays
, 2000
"... Interval timing in the seconds-to-minutes range is be-lieved to underlie a variety of complex behaviors in hu-mans and other animals. One of the more interesting problems in interval timing is trying to understand how the brain times events lasting for minutes with millisec-ond-based neural processe ..."
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Interval timing in the seconds-to-minutes range is be-lieved to underlie a variety of complex behaviors in hu-mans and other animals. One of the more interesting problems in interval timing is trying to understand how the brain times events lasting for minutes with millisec-ond-based neural processes. Timing models proposing the use of coincidence-detection mechanisms (e.g., the detection of simultaneous activity across multiple neural inputs) appear to be the most compatible with known neural mechanisms. From an evolutionary perspective, coincidence detection of neuronal activity may be a fun-damental mechanism of timing that is expressed across a wide variety of species. BioEssays 22:94–103, 2000.
Conducting a systematic review
- AustralianCriticalCare
, 2000
"... Oxidative stress and impaired cellular longevity in the pancreas and skeletal muscle in metabolic syndrome and type 2 diabetes ..."
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Oxidative stress and impaired cellular longevity in the pancreas and skeletal muscle in metabolic syndrome and type 2 diabetes
An introduction to risk sensitivity: The use of Jensen’s Inequality to clarify evolutionary arguments of adaptation and constraint
- American Zoologist
, 1996
"... SYNOPSIS. I review the basic rationale for risk-sensitive foraging, and ..."
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SYNOPSIS. I review the basic rationale for risk-sensitive foraging, and
Context-dependent, risk-sensitive foraging preferences in wild rufous hummingbirds." Animal Behaviour 58
, 1999
"... We tested the risk-sensitive foraging preferences of wild rufous hummingbirds, Selasphorus rufus, with three types of artificial flowers. All three flower types provided the same mean volume of 30 μl of sucrose, but differed in terms of variability of the reward: constant, low variance and high vari ..."
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We tested the risk-sensitive foraging preferences of wild rufous hummingbirds, Selasphorus rufus, with three types of artificial flowers. All three flower types provided the same mean volume of 30 μl of sucrose, but differed in terms of variability of the reward: constant, low variance and high variance. In trinary comparisons, subjects preferred the low-variance reward over the constant reward, and the constant reward over the high-variance reward; a result not predicted by risk-sensitive foraging theory. However, when tested with traditional binary comparisons, hummingbirds showed conventional risk-averse behaviour and selected the constant reward over the low- or high-variance rewards. This reversal of preference represents a context-dependent foraging preference. The utility of selecting intermediate levels of risk and the source of the preference reversal are discussed relative to risk-sensitive foraging theory and the effects of local context on foraging choices. Animals are sensitive not only to mean foraging intake or energetic return, but also to variation about this mean. Consideration of the stochastic nature of foraging success greatly increases the authenticity of foraging studies. Risk-sensitive foraging has blossomed from its theoretical
doi:10.1006/anbe.2003.2278 The twin threshold model: risk-intermediate foraging by rufous hummingbirds, Selasphorus rufus
, 2002
"... I developed two versions of the twin threshold model (TTM) to assess risk-sensitive foraging decisions by rufous hummingbirds. The model incorporates energy thresholds for both starvation and reproduction and assesses how three reward distributions with a common mean but different levels of variance ..."
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I developed two versions of the twin threshold model (TTM) to assess risk-sensitive foraging decisions by rufous hummingbirds. The model incorporates energy thresholds for both starvation and reproduction and assesses how three reward distributions with a common mean but different levels of variance interact with these critical thresholds to determine fitness. Fitness, a combination of survival and reproduction, is influenced by both the amount of variance in the distributions and the relative position of the common mean between the thresholds. The model predicts that risk-intermediate foraging is often the optimal policy, and that risk aversion is favoured as the common mean of the distributions approaches the starvation threshold, whereas risk preference is favoured as the common mean approaches the reproduction threshold. Tests with free-living hummingbirds supported these predictions. Hummingbirds were presented with three distributions of nectar rewards that had a common mean but Nil, Moderate or High levels of variance. Birds preferred intermediate levels of variance (Moderate) when presented with all three rewards simultaneously, and became more risk-averse as the mean of the distributions was decreased but more risk-prone as the mean was increased. Birds preferred Nil when it was paired with Moderate or with High, but preferred Moderate in the presence of Nil and High together. This reversal of preference is a violation of regularity, conventionally interpreted as irrational choice behaviour. I provide
Meanings of Rationality
"... The concept of rationality differs between psychology, philosophy, economics and biology. For psychologists and philosophers, the emphasis is on the process by which decisions are made: rational beliefs are arrived at by reasoning and contrasted with beliefs arrived at by emotion, faith, authority ..."
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The concept of rationality differs between psychology, philosophy, economics and biology. For psychologists and philosophers, the emphasis is on the process by which decisions are made: rational beliefs are arrived at by reasoning and contrasted with beliefs arrived at by emotion, faith, authority or arbitrary choice. Economists emphasise consistency of choice, regardless of the process and the goal. Biologists use a concept that links both previous ideas. Following Darwin’s theory of natural selection, they expect animals to behave as if they had been designed to surpass the fitness of their conspecifics and use optimality to predict behaviour that might achieve this. I introduce the terms PP-rationality, E-rationality and B-rationality to refer to these three different conceptions, and explore the advantages and weaknesses of each of them. The concepts are first discussed and then illustrated with specific examples of research in bird behaviour, including New Caledonian crows’ tool design, hummingbirds ’ preferences between flowers and starlings’ choices between walking and flying. I conclude that no single definition of rationality can serve the purposes of the research community but that agreement on meanings and justifications for each stand is both necessary and possible.
Cognitive influences on risk-seeking by rhesus macaques
- Judgm. Decis. Mak
, 2008
"... Humans and other animals are idiosyncratically sensitive to risk, either preferring or avoiding options having the same value but differing in uncertainty. Many explanations for risk sensitivity rely on the non-linear shape of a hypothesized utility curve. Because such models do not place any import ..."
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Humans and other animals are idiosyncratically sensitive to risk, either preferring or avoiding options having the same value but differing in uncertainty. Many explanations for risk sensitivity rely on the non-linear shape of a hypothesized utility curve. Because such models do not place any importance on uncertainty per se, utility curve-based accounts predict indifference between risky and riskless options that offer the same distribution of rewards. Here we show that monkeys strongly prefer uncertain gambles to alternating rewards with the same payoffs, demonstrating that uncertainty itself contributes to the appeal of risky options. Based on prior observations, we hypothesized that the appeal of the risky option is enhanced by the salience of the potential jackpot. To test this, we subtly manipulated payoffs in a second gambling task. We found that monkeys are more sensitive to small changes in the size of the large reward than to equivalent changes in the size of the small reward, indicating that they attend preferentially to the jackpots. Together, these results challenge utility curve-based accounts of risk sensitivity, and suggest that psychological factors, such as outcome salience and uncertainty itself, contribute to risky decision-making.
Optimal Robot Recharging Strategies For Time Discounted Labour
"... Energy is defined as the potential to perform work: every system that does some work must possess the required energy in advance. An interesting class of systems, including animals and recharging robots, has to actively choose when to obtain energy and when to dissipate energy in work. If working an ..."
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Energy is defined as the potential to perform work: every system that does some work must possess the required energy in advance. An interesting class of systems, including animals and recharging robots, has to actively choose when to obtain energy and when to dissipate energy in work. If working and collecting energy are mutually exclusive, as is common in many animal and robot scenarios, the system faces an essential two-phase action selection problem: (i) how much energy should be accumulated before starting work; (ii) at what remaining energy level should the agent switch back to feeding/recharging? This paper presents an abstract general model of a energy-managing agent that does time-discounted work. Analyzing the model, we find solutions to both questions that optimise’s the value of the work done. This result is validated empirically by simulated robot experiments that agree closely with the model.
2000 ) Foraging strategies and feeding regimes: web and decoration investment
- in Argiope keyserlingi Karsch (Araneae: Araneidae) . Evolutionary Ecology Research , 2 , 69 – 80
"... ABSTRACT The principal foraging cost for web-building spiders is the amount of silk invested in their webs. Spiders in the genus Argiope additionally decorate their orb webs with conspicuous UVwhite silk bands, called web 'decorations' or 'stabilimenta', which enhance foraging s ..."
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ABSTRACT The principal foraging cost for web-building spiders is the amount of silk invested in their webs. Spiders in the genus Argiope additionally decorate their orb webs with conspicuous UVwhite silk bands, called web 'decorations' or 'stabilimenta', which enhance foraging success by attracting prey to the web. We subjected Argiope keyserlingi Karsch to different feeding regimes and measured their foraging response with respect to the size and design of the orb-web, and the number and length of decorative silk bands. Spiders experiencing low prey encounter rates constructed larger webs and incorporated more silk but fewer web decorations than spiders experiencing high prey encounter rates. When the rate of prey encounter was constant, the spiders increased the amount of silk per web but with little change in the number of decorative bands. In contrast, when prey supply was variable, spiders increased the number of decorative silk bands but not the amount of silk invested in the web.
Rational decision making in primates: the bounded and the ecological. Primate neuroethology Oxford
, 2010
"... A young female rhesus macaque steals furtive glances at the male off to her right. He just arrived to the territory and therefore immediately piques her interest. The alpha male, however, sits a few meters off, basking in the sun. Being in estrus, the young female faces a choice: solicit a mating fr ..."
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A young female rhesus macaque steals furtive glances at the male off to her right. He just arrived to the territory and therefore immediately piques her interest. The alpha male, however, sits a few meters off, basking in the sun. Being in estrus, the young female faces a choice: solicit a mating from the alpha male or follow the unfamiliar male into the brush to sneak a mating with him. Mating with the alpha male almost guarantees ‘good genes ’ for her offspring. But something pushes her towards the unfamiliar male. Mating with him reduces the probability of inbreeding and adds a bit of genetic diversity to her offspring. Additionally, mating with the new male could act as an investment in the future: the current alpha male is getting old, and befriending a prospective alpha male could yield future benefits. In addition, spreading the possibility of paternity may secure protection for the offspring. Yet, this mating also involves risks. Males often vocalize while mating, which attracts the attention of other males. If the unfamiliar male vocalizes, the alpha male may attack the female. Should she take the safe option or risk punishment for possible future payoffs? Primates constantly face decisions which influence their survival and reproduction. Continue foraging in this tree or move on to another? Expose oneself to a hidden predator by straying from the group or enjoy the safety of having other potential victims nearby? Defend one’s territory from invaders or abandon it and
