Primacy Bias Research Articles

A social learning primacy trend in mate-copying: an experiment in Drosophila melanogaster.

Social learning is learning from the observation of how others interact with the environment. However, in nature, individuals often need to process serial social information and may favour either the most recent information (recency bias), constantly updating knowledge to match the environment, or the information that appeared first in the series (primacy bias), which may slow down adjustment to environmental change. Mate-copying is a widespread form of social learning in a mate choice context related to conformity in mate choice, and where a naive individual develops a preference for a given mate (or mate phenotype) seen being chosen by conspecifics. Mate-copying is documented in most vertebrate taxa and in the fruit fly Drosophila melanogaster. Here, we tested experimentally whether female fruit flies show a primacy or a recency bias by presenting pictures of a female copulating with one of two contrastingly coloured male phenotypes. We found that after two sequential contradictory demonstrations, females show a tendency to prefer males of the phenotype preferred in the first demonstration, suggesting that mate-copying in D. melanogaster is not based on the most recently observed mating and may be influenced by a form of primacy bias.

Eliminating Primacy Bias in Online Reinforcement Learning by Self-Distillation.

Excessive invalid explorations at the beginning of training lead deep reinforcement learning process to fall into the risk of overfitting, further resulting in spurious decisions, which obstruct agents in the following states and explorations. This phenomenon is termed primacy bias in online reinforcement learning. This work systematically investigates the primacy bias in online reinforcement learning, discussing the reason for primacy bias, while the characteristic of primacy bias is also analyzed. Besides, to learn a policy generalized to the following states and explorations, we develop an online reinforcement learning framework, termed self-distillation reinforcement learning (SDRL), based on knowledge distillation, allowing the agent to transfer the learned knowledge into a randomly initialized policy at regular intervals, and the new policy network is used to replace the original one in the following training. The core idea for this work is distilling knowledge from the trained policy to another policy can filter biases out, generating a more generalized policy in the learning process. Moreover, to avoid the overfitting of the new policy due to excessive distillations, we add an additional loss in the knowledge distillation process, using L2 regularization to improve the generalization, and the self-imitation mechanism is introduced to accelerate the learning on the current experiences. The results of several experiments in DMC and Atari 100k suggest the proposal has the ability to eliminate primacy bias for reinforcement learning methods, and the policy after knowledge distillation can urge agents to get higher scores more quickly.

Perceptual confirmation bias induces overconfidence in addition to a primacy bias during evidence integration

Perceptual confirmation bias induces overconfidence in addition to a primacy bias during evidence integration

Primacy biases endure the addition of frequency variability

The primacy bias (PB) is a phenomenon that indicates the brain does not always process sensory information as an ‘ideal Bayesian observer’, but rather is disproportionately influenced by first impressions. This study was designed to establish whether a PB observed in auditory event-related potentials (ERPs) to a sequence of sound remained evident in the presence of increased levels of tone frequency variation. Two groups of participants were presented with a novel oddball paradigm, while simultaneously having cortical activity recorded with an EEG. In the control group, participants heard a two-tone sequence where the probability of the two tones of different duration switched after 480 sounds/2.4 min block, so that the tone initially encountered as rare became common and vice versa. The key manipulation introduced in the test group was a change of frequency in each block, removing a key element of regularity. The additional frequency variation resulted in no significant difference in the PB between the groups. The data suggest powerful first learning effects are not disrupted by frequency changes, indicating the robustness of learning heuristics.

Reduced Primacy Bias in Autism during Early Sensory Processing.

Recent theories of autism propose that a core deficit in autism would be a less context-sensitive weighting of prediction errors. There is also first support for this hypothesis on an early sensory level. However, an open question is whether this decreased context sensitivity is caused by faster updating of one's model of the world (i.e., higher weighting of new information), proposed by predictive coding theories, or slower model updating. Here, we differentiated between these two hypotheses by investigating how first impressions shape the mismatch negativity (MMN), reflecting early sensory prediction error processing. An autism and matched control group of human adults (both n = 27, 8 female) were compared on the multi-timescale MMN paradigm, in which tones were presented that were either standard (frequently occurring) or deviant (rare), and these roles reversed every block. A well-replicated observation is that the initial model (i.e., the standard and deviant sound in the first block) influences MMN amplitudes in later blocks. If autism is characterized by faster model updating, and thus a smaller primacy bias, we hypothesized (and demonstrate using a simple reinforcement learning model) that their MMN amplitudes should be less influenced by the initial context. In line with this hypothesis, we found that MMN responses in the autism group did not differ between the initial deviant and initial standard sounds as they did in the control group. These findings are consistent with the idea that autism is characterized by faster model updating during early sensory processing, as proposed by predictive coding accounts of autism.SIGNIFICANCE STATEMENT Recent theories of autism propose that a core deficit in autism is that they are faster to update their models of the world based on new sensory information. Here, we tested this hypothesis by investigating how first impressions shape brain responses during early sensory processing, and hypothesized that individuals with autism would be less influenced by these first impressions. In line with earlier studies, our results show that early sensory processing was influenced by first impressions in a control group. However, this was not the case in an autism group. This suggests that individuals with autism are faster to abandon their initial model, and is consistent with the proposal that they are faster to update their models of the world.

A confirmation bias in perceptual decision-making due to hierarchical approximate inference.

Making good decisions requires updating beliefs according to new evidence. This is a dynamical process that is prone to biases: in some cases, beliefs become entrenched and resistant to new evidence (leading to primacy effects), while in other cases, beliefs fade over time and rely primarily on later evidence (leading to recency effects). How and why either type of bias dominates in a given context is an important open question. Here, we study this question in classic perceptual decision-making tasks, where, puzzlingly, previous empirical studies differ in the kinds of biases they observe, ranging from primacy to recency, despite seemingly equivalent tasks. We present a new model, based on hierarchical approximate inference and derived from normative principles, that not only explains both primacy and recency effects in existing studies, but also predicts how the type of bias should depend on the statistics of stimuli in a given task. We verify this prediction in a novel visual discrimination task with human observers, finding that each observer's temporal bias changed as the result of changing the key stimulus statistics identified by our model. The key dynamic that leads to a primacy bias in our model is an overweighting of new sensory information that agrees with the observer's existing belief-a type of 'confirmation bias'. By fitting an extended drift-diffusion model to our data we rule out an alternative explanation for primacy effects due to bounded integration. Taken together, our results resolve a major discrepancy among existing perceptual decision-making studies, and suggest that a key source of bias in human decision-making is approximate hierarchical inference.

Serial memory for landmarks encountered during route navigation

The present study demonstrates similarities between route learning and classical tests of serial order memory. Here, we investigated serial memory for landmarks in a route learning task, in younger and older adults. We analysed data from a route learning task with 12 landmarks. Participants (88 younger and 77 older) learned a route using either a Fixed Learning (3 exposures to the route) or Flexible Learning (repeated exposures until successful navigation was achieved) procedure. Following route learning, participants completed Immediate Free Recall (IFR) and Free Reconstruction of Order (Free RoO) of the landmarks. We show clear acquisition of sequence memory for landmarks for both age groups, with Free RoO producing a bowed serial position curve. IFR produced recency effects but no primacy effects in fixed learning, with recency reduced following flexible learning for both age groups. Younger adults displayed a primacy bias for the first item recalled in both learning conditions, as did the older adults in the flexible learning condition. In contrast, older adults displayed a recency bias in the fixed learning condition. Evidence of contiguity in IFR was present only for younger adults in the flexible learning condition. Findings are broadly consistent with results from typical short-term list learning procedures and support the universality of sequence learning effects, which we demonstrate are generalisable to a navigation context.

You never forget your first? Impact of interview timing on institutional rank order.

To analyze the impact of interview date on the applicant rank for Neurology residencies in the United States. A multi-institutional retrospective review of interview dates and applicant rank list data for the National Resident Matching Program (NRMP) was conducted for five Neurology programs, totaling 1932 interviewed applicants over a combined total of 31 interview years. For each candidate, the interview date and applicant rank were abstracted along with the total number of interviews for that season. Statistical analyses were completed on the cumulative institution data set as well for each individual institution to assess for a possible relationship between interview date and applicant rank. The cumulative institutional analysis showed that the mean applicant rank decreased as the interview season progressed. Applicants who interviewed on the first day of the interview season were ranked 11.4% higher than those who interviewed on the last interview day. Additionally, applicants interviewed on the first interview day more likely to be ranked higher when compared to all other interview dates. Independent analysis of each program's data identified comparable, statistically significant, differences in mean applicant rank and interview position at three out of the five institutions. This study evaluated the impact of interview order on the ranking of applicants by Neurology residency programs, noting a temporal relationship with applicant rank and interview date. The primacy bias appreciated in our data merits further evaluation in other medical specialties. Strategies to minimize the impact of this bias should be employed by residency programs who use medical matching services.

Autistic traits are related to worse performance in a volatile reward learning task despite adaptive learning rates.

Recent theories propose that autism is characterized by an impairment in determining when to learn and when not. Here, we investigated this hypothesis by estimating learning rates (i.e. the speed with which one learns) in three different environments that differed in rule stability and uncertainty. We found that neurotypical participants with more autistic traits performed worse in a volatile environment (with unstable rules), as they chose less often for the most rewarding option. Exploratory analyses indicated that performance was specifically worse when reward rules were opposite to those initially learned for participants with more autistic traits. However, there were no differences in the adjustment of learning rates between participants with more versus less autistic traits. Together, these results suggest that performance in volatile environments is lower in participants with more autistic traits, but that this performance difference cannot be unambiguously explained by an impairment in adjusting learning rates.

Setting precedent: Initial feature variability affects the subsequent precision of regularly varying sound contexts.

The task of making sense of the world around us is supported by brain processes that simplify the environment. For example, repetitive patterns of sensory input help us to predict future events. This study builds on work, suggesting that sensory predictions are heavily influenced by first impressions. We presented healthy adults with a sequence comprising three sounds each differing from the other two on three dimensions; for simplicity A, B and C. These three sounds were arranged in blocks where two were equally common and one was rare, and the probabilities rotated creating three different block types (i.e., probabilities, A<B=C, B<A=C, C<A=B). Sequences included two of each block type with three versions-one starting with A<B=C, one with B<A=C and one with C<A=B. The common tone evoked responses in any given block were highly suppressed consistent with the auditory system predicting regular events, while the rare tone in each block elicited a larger response signaling a prediction error. However, results indicated that the auditory system assessed the configurations in which the two common tones were adjacent in space (within the three locations used) as less volatile compared to when they were highly separate. When the more volatile environment was encountered at the beginning of the sequence, all deviance-related responses were significantly lower in amplitude. Results suggest that the representation of a stimulus configuration is affected by the estimate drawn from the initial context, expanding our notion of the nature of primacy bias to include powerful effects of initial feature variance.

Revealed Expectations and Learning Biases: Evidence from the Mutual Fund Industry

By inverting the optimal portfolios of mutual fund managers in a fairly general setting, which allows us to partial out the effect of risk aversion and hedging demands, we provide an estimate of perceived expected excess returns and show that they are significantly affected by experienced returns. The effect of past returns is non-monotone: we provide reduced-form and structural evidence of managers displaying recency and primacy bias. Finally, we estimate an average coefficient of relative risk aversion close to unity.

Do Researchers Anchor Their Beliefs on the Outcome of an Initial Study?

As a research field expands, scientists have to update their knowledge and integrate the outcomes of a sequence of studies. However, such integrative judgments are generally known to fall victim to a primacy bias where people anchor their judgments on the initial information. In this preregistered study we tested the hypothesis that people anchor on the outcome of a small initial study, reducing the impact of a larger subsequent study that contradicts the initial result. Contrary to our expectation, undergraduates and academics displayed a recency bias, anchoring their judgment on the research outcome presented last. This recency bias is due to the fact that unsuccessful replications decreased trust in an effect more than did unsuccessful initial experiments. We recommend the time-reversal heuristic to account for temporal order effects during integration of research results.

Recommendations for use of balanced presentation order of terms in CATA questions

Balancing presentation order of the terms of a CATA question between and within participants has been recommended to minimize the influence of primacy bias on consumer responses and maintain their attention throughout the task. Compared to balancing presentation order only between participants, this experimental factor may make the task more difficult/tedious for participants and shift their attention away from the sensory characterization task with possible detrimental effects for sample discrimination. The aim of the present work was to compare sensory product characterizations obtained using CATA questions in which presentation order of the terms was balanced between participants with those obtained using CATA questions in which presentation order of the terms was balanced both between and within participants. Nine studies with 1028 consumers involving different product categories were conducted. Between-subjects experimental designs were used in all studies. No major differences were found in the sensory product characterizations obtained using presentation orders balanced between participants (BB) and both between and within participants (BW).

Does Sequence Foreknowledge or Concurrent Task Affect First-Impression Bias in Mismatch Negativity?

Event Abstract Back to Event Does Sequence Foreknowledge or Concurrent Task Affect First-Impression Bias in Mismatch Negativity? Jade D. Frost1*, Kelly McDonnell1, Alexander L. Provost1 and Juanita Todd1 1 University of Newcastle, Psychology, Australia The auditory system accumulates evidence about regularity across varying timescales to model predictions about subsequent sound. The evoked-potential component mismatch-negativity (MMN) is elicited upon detection of any pattern-deviation and reflects a ‘prediction-error’. MMN amplitude is proportional to ‘confidence’ in underlying predictions; MMN is largest when patterns are very stable. Using a ‘multi-timescale’ paradigm, we have consistently demonstrated that MMN amplitude does not faithfully reflect sequence stability but instead succumbs to a ‘first-impression bias’ that is coupled to initial tone roles. In the paradigm participants hear two-tone sequences in which tones alternate roles of standard (p = .875) and deviant (p = .125). In stable sequences, roles alternate every 2.4min (480 tones per block; 420-standard, 60-deviant). In unstable sequences, roles alternate every 0.8min (160 tones per block; 140-standard, 20-deviant). The first-impression bias refers to the observation that only MMN in the first stimulus configuration show the expected stability-modulation (stable>unstable). To date all multi-timescale paradigms have been presented while participants have no knowledge of the sequence structure and watch a silent movie. In this study, we attempted to disrupt the bias by modifying engagement of higher-level brain areas in monitoring longer-term patterns thought to underpin it. The primacy bias pattern did not occur when participants performed a demanding concurrent N-Back task (study-1) or were first informed about the sequence structure (study-2) before watching a silent movie. Our results are interpreted as evidence that engagement of higher-order brain areas is required to make predictions about patterning over longer timescales. References Friston, K. (2005). A theory of cortical responses. Philos Trans R Soc Lond B Biol Sci, 360, 815-836. Owen, A. M., McMillan, K. M., Laird, A. R., & Bullmore, E. (2005). N-back working memory paradigm: A meta-analysis of normative functional neuroimaging studies.Human Brain Mapping, 25, 46-59. Mullens, D., Woodley, J., Whitson, L., Provost, A., Heathcote, A., Winkler, I., & Todd, J. (2014). Altering the primacy bias—How does a prior task affect mismatch negativity? Psychophysiology, 51, 437-445. Todd, J., Provost, A., Cooper, G. (2011). Lasting first impressions: A conservative bias in automatic filters of the acoustic environment. Neuropsychologia, 49, 3399-3405. Todd, J., Heathcote, A., Mullens, D., Whitson, L. R., Provost, A., & Winkler, I. (2013). What controls gain in gain control? Mismatch negativity (MMN), priors and system biases. Brain topography, 1-12. Winkler, I., Karmos, G., & Näätänen, R. (1996). Adaptive modeling of the unattended acoustic environment reflected in the mismatch negativity event-related potential. Brain research, 742, 239-252. Keywords: context, Bias, First-impressions, auditory, Mismatch Negativity., ERP/EEG, predictive coding, salience coding, Prediction error Conference: ASP2015 - 25th Annual Conference of the Australasian Society for Psychophysiology, Sydney, Australia, 2 Dec - 4 Dec, 2015. Presentation Type: Poster Presentation Topic: Psychophysiology Citation: Frost JD, McDonnell K, Provost AL and Todd J (2015). Does Sequence Foreknowledge or Concurrent Task Affect First-Impression Bias in Mismatch Negativity?. Conference Abstract: ASP2015 - 25th Annual Conference of the Australasian Society for Psychophysiology. doi: 10.3389/conf.fnhum.2015.219.00044 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 28 Sep 2015; Published Online: 30 Nov 2015. * Correspondence: Miss. Jade D Frost, University of Newcastle, Psychology, Newcastle, New South Wales, 2300, Australia, jade.frost@uon.edu.au Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Jade D Frost Kelly McDonnell Alexander L Provost Juanita Todd Google Jade D Frost Kelly McDonnell Alexander L Provost Juanita Todd Google Scholar Jade D Frost Kelly McDonnell Alexander L Provost Juanita Todd PubMed Jade D Frost Kelly McDonnell Alexander L Provost Juanita Todd Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Does naturally occurring high salience for speech sounds impact the primacy bias observed in mismatch negativity (MMN)?

Event Abstract Back to Event Does naturally occurring high salience for speech sounds impact the primacy bias observed in mismatch negativity (MMN)? Daniel Mullens1, 2*, Alex Provost1, 2, István Winkler3, 4 and Juanita Todd1, 2* 1 University of Newcastle, Australia 2 Priority Research Centre for Brain and Mental Health , Australia 3 Institute of Cognitive Neuroscience and Psychology, Hungary 4 Institute of Psychology, Hungary Background: Mismatch negativity (MMN) is elicited when a "standard" regularity within an acoustic sequence is violated. MMN is large if a deviation is highly different physically and/or is very rare. MMN size is also proportional to pattern stability over time; however, our research has demonstrated an order-driven bias affecting how stability modulates MMN size. In sequences of pure tones alternating roles as standard and deviant, only MMN to the first encountered deviant tone-type is modulated by pattern stability. Our prior research has shown that assigning behavioural salience to the tones (in a target detection task) disrupted this bias. The present study was designed to determine whether the bias would be observed when the sequence contained speech sounds (high in natural salience) instead of pure tones. Methods: Participants (n=7) heard sequences in which two phonemes (/a/ and /i/) alternated roles as a repetitive standard (p= 0.875) and a rare deviant (p=0.125). Roles alternated in blocks in slow or fast changing sequences (every 2.4 vs 0.8 min, respectively). MMN to each sound as a deviant was compared between fast and slow sequences and at transition points (early in a block) versus later when the roles stabilized. Results: Two patterns defining the bias were significant. An order x sequence effect was present at transition points with MMN to the first deviant larger in slow than fast sequences but did not differ for the first standard as a later deviant (p<.05). For the first deviant, MMN in slow sequence blocks was large at transitions and stayed large over a block while that to the first standard as a later deviant started small at transition and grew with stability (p<.05). Discussion: The data expose that the same order-driven bias seen in our prior studies also occurs for speech sounds. Initial exposure within a sound sequence produces a long timescale modulation of how perceptual inference is reflected in MMN size. Keywords: salience, stability, MMN, Primacy bias, MMN Size Conference: XII International Conference on Cognitive Neuroscience (ICON-XII), Brisbane, Queensland, Australia, 27 Jul - 31 Jul, 2014. Presentation Type: Poster Topic: Memory and Learning Citation: Mullens D, Provost A, Winkler I and Todd J (2015). Does naturally occurring high salience for speech sounds impact the primacy bias observed in mismatch negativity (MMN)?. Conference Abstract: XII International Conference on Cognitive Neuroscience (ICON-XII). doi: 10.3389/conf.fnhum.2015.217.00228 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 19 Feb 2015; Published Online: 24 Apr 2015. * Correspondence: Mr. Daniel Mullens, University of Newcastle, Newcastle, Australia, c3072889@uon.edu.au Dr. Juanita Todd, University of Newcastle, Newcastle, Australia, juanita.todd@newcastle.edu.au Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Daniel Mullens Alex Provost István Winkler Juanita Todd Google Daniel Mullens Alex Provost István Winkler Juanita Todd Google Scholar Daniel Mullens Alex Provost István Winkler Juanita Todd PubMed Daniel Mullens Alex Provost István Winkler Juanita Todd Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Does primacy bias occur in mismatch negativity (MMN) to spatial deviants?

Does primacy bias occur in mismatch negativity (MMN) to spatial deviants?

Cognitive biases and design effects in experimental auctions

Purpose – Experimental auctions are widely used as a non-hypothetical value elicitation method to examine consumer preferences for novel, controversial foods. However, despite its advantages over hypothetical methods, its practice might lead to a wide variety of biases. The purpose of this paper is to provide a list of key cognitive biases and design effects in food auction research and to deliver scientifically underpinned procedures in order to assess, control and reduce them. Its applicability and relevance is examined in auctions on willingness-to-pay for folate (GM) biofortified rice. Design/methodology/approach – Based on auction literature, a list of 18 biases has been developed. Experimental auctions were conducted with 252 women from Shanxi Province, China to test the occurrence of eight biases, while demonstrating measures to reduce the risk of ten biases. Findings – The results lend support for three information-related effects, i.e. confirmation bias, conflicting product information effects and a primacy bias, but not for a multiple-good valuation effect, a panel size effect, a trial winner effect and time-related sampling biases. Furthermore, there are no clear indications of social desirability bias, auction fever and a false consensus effect. Research limitations/implications – This study emphasizes the need to take into account, and measure the risk of various biases when developing, organizing and interpreting experimental auctions. Future research should further extend the list of biases and validate the study findings. Originality/value – By using a highly topical subject, this study is one of the first to address the potential risk of cognitive biases and design effects in experimental (food) auctions.

Mismatch negativity (MMN) to pitch change is susceptible to order-dependent bias.

Pattern learning facilitates prediction about upcoming events. Within the auditory system such predictions can be studied by examining effects on a component of the auditory-evoked potential known as mismatch negativity (MMN). MMN is elicited when sound does not conform to the characteristics inferred from statistical probabilities derived from the recent past. Stable patterning in sequences elevates confidence in automatically generated perceptual inferences about what sound should come next and when. MMN amplitude should be larger when sequence is highly stable compared to when it is more volatile. This expectation has been tested using a multi-timescale paradigm. In this study, two sounds of different duration alternate roles as a predictable repetitive “standard” and rare MMN-eliciting “deviation.” The paradigm consists of sound sequences that differ in the rate at which the roles of two tones alternate, varying from slowly changing (high stability) to rapidly alternating (low stability). Previous studies using this paradigm discovered a “primacy bias” affecting how stability in patterning impacts MMN amplitude. The primacy bias refers to the observation that the effect of longer-term stability within sequences only appears to impact MMN to the sound first encountered as deviant (the sound that is rare when the sequence commences). This study determines whether this order-driven bias generalizes to sequences that contain two tones differing in pitch. By manipulating (within-subjects) the order in which sounds are encountered as deviants the data demonstrate the two defining characteristics of primacy bias: (1) sequence stability only ever impacts MMN amplitude to the first-deviant sound; and (2) within higher stability sequences, MMN is significantly larger when a sound is the first compared to when it is the second deviant. The results are consistent with a general order-driven bias exerting modulating effects on MMN amplitude over a longer timescale.

Altering the primacy bias—How does a prior task affect mismatch negativity?

The role in which two tones are first encountered in an unattended oddball sequence affects how deviance detection, reflected by mismatch negativity, treats them later when the roles reverse: a "primacy bias." We tested whether this effect is modulated by previous behavioral relevance assigned to the two tones. To this end, sequences in which the roles of the two tones alternated were preceded by a go/no-go task in which tones were presented with equal probability. Half of the participants were asked to respond to the short sounds, the other half to long sounds. Primacy bias was initially abolished but returned dependent upon the go-stimulus that the participant was assigned. Results demonstrate a long-term impact of prior learning on deviance detection, and that even when prior importance/equivalence is learned, the bias ultimately returns. Results are discussed in terms of persistent go-stimulus specific changes in responsiveness to sound.

Role of Information on Consumers’ Willingness‐to‐pay for Genetically‐modified Rice with Health Benefits: An Application to China

Despite their potential health benefits, the controversial nature surrounding the use of GM technology in biofortified crops remains a subject of discussion. This paper investigates the role of information on willingness‐to‐pay for folate‐biofortified rice in a Chinese folate‐deficient region. We conducted second price auctions with 252 women of childbearing age, split up into two target groups based on street (n = 132, non‐student sample) or school auctions (n = 120, student sample). Notwithstanding a general positive effect of folate‐related information (i.e. content, benefits and regional situation), evidence reveals that the non‐student sample is less concerned about GM technology. The results also provide insight into serial position effects in conflicting GM information. Whereas participants in the non‐student sample are more prone to a primacy bias when receiving both positive and negative information, an alarmist reaction is observed in the student sample. This study highlights the need for segmented, targeted communication strategies on biofortification.