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The past decades have seen tremendous progress in fundamental studies on economic choice in humans. However, elucidation of the underlying neuronal processes requires invasive neurophysiological studies that are met with difficulties in humans. Monkeys as evolutionary closest relatives offer a solution. The animals display sophisticated and well-co...
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... and logit link function, repeating the procedure for each human participant and for each 178 monkey session. We then plotted the betas of each model in a three-dimensional scatter plot after 179 normalization (deducting the minimum value and log10 transformation) and after removing outliers 180 with more than three median absolute deviations (Fig. ...
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... GLM for each human participant and one GLM for each monkey session. As 291 choices were not repeated in the individual human participants, we set up the model to predict 292 single binary choices; the analysis used a binomial distribution and logit link function in the GLM. We 293 found similar ranges of beta coefficients across the two species (Fig. 3B), suggesting similarity in risky 294 choices between humans and monkeys. 295 . CC-BY 4.0 International license perpetuity. It is made available under a preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint ...
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... test; Fig. 4A); vice versa, when preferring option B to A, they also preferred option C to D ('reverse 312 Allais-type' ; Fig. 4B); see Fig. S2 for additional tests in both directions. These violations differed 313 between the two monkeys (Fig. 4, top vs. middle). Interestingly, choice variability may partly explain 314 IA violations in monkeys (Fig. S3). 315 316 ...
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... 2007), our study on monkeys tested choices repeatedly. The repeated choices 395 reduced the chance of mistakes and noise that might explain some axiom violations (Blavatskyy, 396 2007;Hey & Orme, 1994). The probability of IA violations was positively correlated with choice 397 variability (standard deviation of choice probability; Fig. S3), which might be explained by the 398 observation that most violations occurred close to the indifference points and curves of the ...
Citations
... The way RS was measured in the present study was unique in several ways making it useful as a novel approach, but also difficult to match with previous work on RS. The paradigm differs from typical work on preference using intertemporal choice (Bujold et al., 2022;Seak et al., 2023) by evaluating preference from 'imperative' or forced choice trials. Relative reward functioning is a part of all choice paradigms, but only behavioral tasks that provide a clear reference and compare relative and absolute reward contexts can directly gauge reward updating (Flaherty, 1996). ...
Addiction involves key impairments in reward sensitivity (RS). The current study explored impaired RS to
natural reward as a predisposing factor to addictive-like behavior. Alcohol preferring (P) rats are selectively bred
based on significantly greater ethanol consumption and preference and offer the ability to inspect differences in
subjects with a positive family history of addictive-like behavior. P rat’s RS was compared to RS in the well-used
Sprague-Dawley (SD) strain. To assess RS in a novel manner, instrumental incentive contrast, discrimination and
consumption of sucrose solution were examined. Animals performed in a free operant situation for different
sucrose concentration solutions using a block of ‘mixed’ trials with alternating outcome concentrations (e.g., 5
and 10 % sucrose) to change outcome value in a predictable manner. Animals also performed for reward in
blocks of single outcome trials (5 or 10 or 20 or 40 % sucrose daily exposure) surrounding the mixed block. RS (e.
g., reward discrimination and contrast effects between and within-sessions) was measured by changes in trials
completed, instrumental response latency and consumption. P rats expressed an altered profile of RS with a
greater tendency toward equivalent responding to different outcomes within the same session and an absence of
incentive contrast from diverse reward comparisons. In contrast, SD animals expressed within-session reward
discrimination and a subset of incentive contrast effects. These effects were moderated by food deprivation more
consistently in SD compared to P rats. P rat alterations in processing natural rewards could predispose them to
addictive-like behaviors including greater alcohol consumption and preference.