Anxiety-induced cognitive bias in non-human animals

University of Bristol, Bristol, BS40 5DU, UK.
Physiology & Behavior (Impact Factor: 2.98). 07/2009; 98(3):345-50. DOI: 10.1016/j.physbeh.2009.06.012
Source: PubMed


As in humans, 'cognitive biases' in the way in which animals judge ambiguous stimuli may be influenced by emotional state and hence a valuable new indicator of animal emotion. There is increasing evidence that animals experiencing different emotional states following exposure to long-term environmental manipulations show contrasting biases in their judgement of ambiguous stimuli. However, the specific type of induced emotional state is usually unknown. We investigated whether a short-term manipulation of emotional state has a similar effect on cognitive bias, using changes in light intensity; a treatment specifically related to anxiety-induction. Twenty-four male rats were trained to discriminate between two different locations, in either high ('H') or low ('L') light levels. One location was rewarded with palatable food and the other with aversive food. Once the rats had shown spatial discrimination, by running significantly faster to the rewarded location, they were tested with three ambiguous locations intermediate between the rewarded and aversive locations, and their latency to approach each location recorded. Half the rats were tested in the same light levels as during training, the remainder were switched. Rats switched from high to low light levels (putatively the least negative emotional manipulation) ran significantly faster to all three ambiguous probes than those rats switched from low to high light levels (putatively the most negative manipulation). This suggests that the judgement bias technique might be useful as an indicator of short-term changes in anxiety for non-human animals.

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    • "r in which the ambiguous conditions were presented was also balanced across sessions to control for any order effects . Between trials the large compartment combinations were manipulated by removing and replacing the floor covers to transition to the combinations needed for the next trial . The goal pots in the ambiguous conditions were unbaited ( Burman et al . , 2009 ) . In the reward and aversive trials , rats were allowed to eat the available pellets until the conclusion of the trial , at which time the rat was removed from the apparatus . The CPP apparatus was wiped down with a 70% alcohol solution between each trial to remove any olfactory information left behind from the previous trial . Latenc"
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    ABSTRACT: The effect of oxytocin on cognitive bias was investigated in rats in a modified conditioned place preference paradigm. Fifteen male rats were trained to discriminate between two different cue combinations, one paired with palatable foods (reward training), and the other paired with unpalatable food (aversive training). Next, their reactions to two ambiguous cue combinations were evaluated and their latency to contact the goal pot recorded. Rats were injected with either oxytocin (OT) or saline with the prediction that rats administered OT would display a shorter average latency to approach on ambiguous trials. There was no significant difference between latencies to approach on ambiguous trials compared to reward trials, but the rats were significantly slower on the aversive compared to the ambiguous conditions. Oxytocin did not affect approach time; however, it was unclear, after follow-up testing, whether the OT doses tested were sufficient to produce the desired effects on cognitive bias. Future research should consider this possibility.
    Frontiers in Psychology 10/2015; 6. DOI:10.3389/fpsyg.2015.01306 · 2.80 Impact Factor
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    • "It is becoming increasingly accepted that the capacity for anxiety has evolved as a regulatory mechanism for fear [2] [3] [4] [5] [6] [7]. Greater anxiety causes an individual to be alert to more subtle signs of potential danger, while lowered anxiety causes the individual to respond with fear only to more obvious signs [8]. As unpleasant as the experience of anxiety may be, the capacity for anxiety is beneficial because it allows an individual to modulate fearfulness according to current vulnerability. "
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    ABSTRACT: Normal anxiety is considered an adaptive response to the possible presence of danger, but it appears highly susceptible to dysregulation. Anxiety disorders are prevalent at high frequency in contemporary human societies, yet impose substantial disability upon their sufferers. This raises a puzzle: why has evolution left us vulnerable to anxiety disorders? We develop a signal detection model in which individuals must learn how to calibrate their anxiety responses: they need to learn which cues indicate danger in the environment. We study the optimal strategy for doing so, and find that individuals face an inevitable exploration-exploitation tradeoff between obtaining a better estimate of the level of risk on one hand, and maximizing current payoffs on the other. Because of this tradeoff, a subset of the population becomes trapped in a state of excessive and self-perpetuating anxiety, even when individuals learn optimally. This phenomenon arises because when individuals become too cautious, they stop sampling the environment and fail to correct their misperceptions, whereas when individuals become too careless they continue to sample the environment and soon discover their mistakes. We suggest that this process may be involved in the development of excessive anxiety in humans.
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    • "A negative affective state leads to an expectation of negative outcomes and thus a negative bias in the interpretation of ambiguous signals. This has been referred to in the animal literature as pessimism [7], [8]. In contrast, a positive affective state leads to an expectation of positive outcomes and positive biases in signal interpretation, which has been referred to as optimism [9], [10]. "
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    ABSTRACT: Recent advances in animal welfare science used judgement bias, a type of cognitive bias, as a means to objectively measure an animal's affective state. It is postulated that animals showing heightened expectation of positive outcomes may be categorised optimistic, while those showing heightened expectations of negative outcomes may be considered pessimistic. This study pioneers the use of a portable, automated apparatus to train and test the judgement bias of dogs. Dogs were trained in a discrimination task in which they learned to touch a target after a tone associated with a lactose-free milk reward and abstain from touching the target after a tone associated with water. Their judgement bias was then probed by presenting tones between those learned in the discrimination task and measuring their latency to respond by touching the target. A Cox's Proportional Hazards model was used to analyse censored response latency data. Dog and Cue both had a highly significant effect on latency and risk of touching a target. This indicates that judgement bias both exists in dogs and differs between dogs. Test number also had a significant effect, indicating that dogs were less likely to touch the target over successive tests. Detailed examination of the response latencies revealed tipping points where average latency increased by 100% or more, giving an indication of where dogs began to treat ambiguous cues as predicting more negative outcomes than positive ones. Variability scores were calculated to provide an index of optimism using average latency and standard deviation at cues after the tipping point. The use of a mathematical approach to assessing judgement bias data in animal studies offers a more detailed interpretation than traditional statistical analyses. This study provides proof of concept for the use of an automated apparatus for measuring cognitive bias in dogs.
    PLoS ONE 09/2014; 9(9):e107794. DOI:10.1371/journal.pone.0107794 · 3.23 Impact Factor
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