Shifts in Postdiscrimination Gradients Within a Stimulus Dimension Based on Bilateral Facial Symmetry

Derenne, Adam

doi:10.1901/jeab.2010.93-485

Cited by 16 publications

(18 citation statements)

References 46 publications

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“…The average behavioral generalization gradient during the test phase is depicted in Figure 3A. In line with previous findings (Purtle, 1973;Wisniewski et al, 2009;Derenne, 2010), we found a strong peak shift, i.e., the peak of the generalization gradient was displaced from the CSϩ, in the direction away from the CSϪ (t test between responses left vs right of the CSϩ; t ϭ 3.28, p Ͻ 0.01). Moreover, response times (RTs) were modulated by the orientation of the stimulus (one-way ANOVA with repeated measures, F (14,308) ϭ 4.83, p Ͻ 0.001) and revealed a similar gradient as the behavioral responses (higher RT with higher probability of ϩ responses).…”

Section: Behavioral Generalization Gradientsupporting

confidence: 91%

“…Although the test stimuli have never been paired with reward, animals respond to test stimuli that are similar to the CSϩ. A key finding in these experiments is the peak shift (Purtle, 1973;Wisniewski et al, 2009;Derenne, 2010): the peak of the generalization gradient is displaced from the CSϩ, in the direction away from the CSϪ, thereby enhancing the subjective difference between CSϩ and CSϪ.…”

Section: Introductionmentioning

confidence: 99%

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How Glitter Relates to Gold: Similarity-Dependent Reward Prediction Errors in the Human Striatum

et al. 2012

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Optimal choices benefit from previous learning. However, it is not clear how previously learned stimuli influence behavior to novel but similar stimuli. One possibility is to generalize based on the similarity between learned and current stimuli. Here, we use neuroscientific methods and a novel computational model to inform the question of how stimulus generalization is implemented in the human brain. Behavioral responses during an intradimensional discrimination task showed similarity-dependent generalization. Moreover, a peak shift occurred, i.e., the peak of the behavioral generalization gradient was displaced from the rewarded conditioned stimulus in the direction away from the unrewarded conditioned stimulus. To account for the behavioral responses, we designed a similarity-based reinforcement learning model wherein prediction errors generalize across similar stimuli and update their value. We show that this model predicts a similarity-dependent neural generalization gradient in the striatum as well as changes in responding during extinction. Moreover, across subjects, the width of generalization was negatively correlated with functional connectivity between the striatum and the hippocampus. This result suggests that hippocampus-striatal connections contribute to stimulus-specific value updating by controlling the width of generalization. In summary, our results shed light onto the neurobiology of a fundamental, similarity-dependent learning principle that allows learning the value of stimuli that have never been encountered.

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Section: Behavioral Generalization Gradientsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

How Glitter Relates to Gold: Similarity-Dependent Reward Prediction Errors in the Human Striatum

et al. 2012

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“…The sheep individuals however differed in their actions, with four out of six rams clearly avoiding the ergot-containing forage, and two always trying to eat from the container they first approached. The variance in behaviour among individuals, which is common in choice experiments on learning behaviour (e.g., [47]), may be due to the individual characters and abilities, either in adjusting to short-term experimental settings or in the ability to detect and/or avoid ergot. With the latter, there may also have been differences in ergot-related history between the rams, e.g.…”

Section: Discussionmentioning

confidence: 99%

Is the Pathogenic Ergot Fungus a Conditional Defensive Mutualist for Its Host Grass?

Wäli

Saikkonen

et al. 2013

PLoS ONE

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It is well recognized, that outcomes of mutualistic plant-microorganism interactions are often context dependent and can range from mutualistic to antagonistic depending on conditions. Instead, seemingly pathogenic associations are generally considered only harmful to plants. The ergot fungus (Claviceps purpurea) is a common seed pathogen of grasses and cereals. Ergot sclerotia contain alkaloids which can cause severe toxicity in mammals when ingested, and thus the fungal infection might provide protection for the host plant against mammalian herbivores. Theoretically, the net effect of ergot infection would positively affect host seed set if the cost is not too high and the defensive effect is strong enough. According to our empirical data, this situation is plausible. First, we found no statistically significant seed loss in wild red fescue (Festuca rubra) inflorescences due to ergot infection, but the seed succession decreased along increasing number of sclerotia. Second, in a food choice experiment, sheep showed avoidance against forage containing ergot. Third, the frequency of ergot-infected inflorescences was higher in sheep pastures than surrounding ungrazed areas, indicating a protective effect against mammalian grazing. We conclude that, although ergot can primarily be categorized as a plant pathogen, ergot infection may sometimes represent indirect beneficial effects for the host plant. Ergot may thus serve as a conditional defensive mutualist for its host grass, and the pathogenic interaction may range from antagonistic to mutualistic depending on the situation.

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“…The procedure for generating the face stimuli was similar to that described by Derenne (2010). Each time a set of stimuli was created, a photograph of a face was taken with a Sony Cyber-Shot DSC-w1 5.1 megapixel digital camera.…”

Section: Methodsmentioning

confidence: 99%

“…That is, in these cases it is possible to identify stimuli that function in a similar manner as S+and S-, and the organism tends to respond to relatively extreme stimuli (i.e., stimuli very different from S-). Examples include the evolution of sexual dimorphism (ten Cate et al 2006;Weary et al 1993) and aposematic coloration (Gamberale and Tullberg 1996;Gamberale-Stille and Tullberg 1999;Yachi and Higashi 1998), the preference for supernormal stimuli and caricatures (Ghirlanda andEnquist 1999, 2003;Ramachandran and Hirstein 1999;Zimmer 2003), changes in speech patterns (Martindale 2006), and extreme responses in certain forms of mental illness (Derenne 2010;Dunsmoor et al 2009Dunsmoor et al , 2011.…”

Section: Patterns Of Stimulus Generalization Vary With Experiencementioning

confidence: 99%

Postdiscrimination Gradients With Familiar and Unfamiliar Faces

2014

Self Cite

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Discrimination training is often used to improve accuracy in stimulus recognition. However, intradimensional discrimination training with a single positive exemplar and a single negative exemplar may reduce accuracy during a generalization test. More specifically, discrimination training can cause a shift in responding from the positive exemplar to stimuli unlike the negative exemplar. Previous studies have shown that the length of discrimination training affects the degree to which a shift occurs. We sought to determine whether pre-experimental exposure ("familiarity") to the stimuli would have a similar effect. Twenty participants were trained and tested with two different sets of facial images. Each set of images consisted of stimuli that ranged from the naturally asymmetrical version of the face to a symmetrical version of the face. In one condition, the images were based on the participant's own face; in the second condition, the images were based on the face of a stranger. In both cases, the median face served as the positive exemplar. In half of the conditions the naturally asymmetrical face served as the negative exemplar, and in the other half, the symmetrical face served as the negative exemplar. Images based on a stranger's face produced greater generalization than images based on the participant's own face. A significant gradient shift occurred only with familiar faces.

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Shifts in Postdiscrimination Gradients Within a Stimulus Dimension Based on Bilateral Facial Symmetry

Cited by 16 publications

References 46 publications

How Glitter Relates to Gold: Similarity-Dependent Reward Prediction Errors in the Human Striatum

How Glitter Relates to Gold: Similarity-Dependent Reward Prediction Errors in the Human Striatum

Is the Pathogenic Ergot Fungus a Conditional Defensive Mutualist for Its Host Grass?

Postdiscrimination Gradients With Familiar and Unfamiliar Faces

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