Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Effects of Early and Current Environmental Enrichment on Behavior and Growth in Pigs
    Luo, Lu ; Reimert, Inonge ; Middelkoop, Anouschka ; Kemp, Bas ; Bolhuis, J.E. - \ 2020
    Frontiers in Veterinary Science 7 (2020). - ISSN 2297-1769
    behavior - early life - environmental enrichment - feed intake - growth - pigs

    Enriched environments are known to beneficially affect the behavior of pigs, as compared with barren pens. The influence of enrichment may, however, depend on pigs' early life housing experiences. The aim of this study was to investigate the long-term effects of early and later life environmental enrichment on behavior and growth in pigs with different coping styles. Pigs were housed in either barren pens or in larger pens enriched with rooting substrates from birth, and half of them experienced a housing switch, i.e., a loss or gain of enrichment, at 7 weeks of age, creating four treatment groups. Home pen behavior and body weight were recorded until 19 weeks of age. Pigs were classified as reactive or proactive based on a backtest at 2 weeks of age. Enrichment increased time spent exploring, chewing, and play and decreased oral manipulation of penmates and pen-directed exploring and chewing. Behavior of pigs that switched from barren to enriched pens or vice versa reflected not only their actual environment, but also their early life housing. As early and later life enrichment affected most behaviors in opposite directions, effects of enrichment, or lack thereof, after the switch were more pronounced in pigs that had experienced a different early life condition. For instance, pigs experiencing an upgrade from barren to enriched pens seemed to “catch-up” by showing more exploration and play. Conversely, pigs exposed to a downgrade displayed more oral manipulation of penmates than ones kept barren throughout, which particularly held for pigs with a reactive coping style. Effects of early life and current housing on several other behaviors depended on coping style too. Pigs housed in enriched conditions appeared better able to cope with weaning than barren housed pigs, as they gained more weight and had higher feed intake post-weaning. Barren housed pigs had a lower body weight than enriched pigs just before the switch, after which growth was mainly determined by actual housing, with enriched kept pigs having a higher feed intake and body weight. Thus, not only current housing conditions, but also a (mis)match with the early life environment may affect behavior and growth of pigs.

    Methodologies for Assessing Disease Tolerance in Pigs
    Nakov, Dimitar ; Hristov, Slavcha ; Stankovic, Branislav ; Pol, Françoise ; Ivan Dimitrov, Ivan ; Dixhoorn, I.D.E. van - \ 2019
    - p. 12 - 12.
    behavior - disease tolerance - environment - performance - stress
    Features of intensive farming can seriously threaten pig homeostasis, well-being and productivity. Disease tolerance of an organism is the adaptive ability in preserving homeostasis and at the same time limiting the detrimental impact that infection can inflict on its health and performance without affecting pathogen burden per se. While disease resistance (DRs) can be assessed measuring appropriately the pathogen burden within the host, the tolerance cannot be quantified easily. Indeed, it requires the assessment of the changes in performance as well as the changes in pathogen burden. In this paper, special attention is given to criteria required to standardize methodologies for assessing disease tolerance (DT) in respect of infectious diseases in pigs. The concept is applied to different areas of expertise and specific examples are given. The basic physiological mechanisms of DT are reviewed. Disease tolerance pathways, genetics of the tolerance-related traits, stress and disease tolerance, and role of metabolic stress in DT are described. In addition, methodologies based on monitoring of growth and reproductive performance, welfare, emotional affective states, sickness behavior for assessment of disease tolerance, and methodologies based on the relationship between environmental challenges and disease tolerance are considered. Automated Precision Livestock Farming technologies available for monitoring performance, health and welfare-related measures in pig farms, and their limitations regarding DT in pigs are also presented. Since defining standardized methodologies for assessing DT is a serious challenge for biologists, animal scientists and veterinarians, this work should contribute to improvement of health, welfare and production in pigs.
    Public Bureaucracy and Climate Change Adaptation
    Biesbroek, Robbert ; Peters, B.G. ; Tosun, Jale - \ 2018
    Review of Policy Research 35 (2018)6. - ISSN 1541-132X - p. 776 - 791.
    adaptación al cambio climático - administrative traditions - behavior - burocracias públicas - climate change adaptation - comportamiento

    Despite recognizing the importance of public bureaucracies in governing climate change, our knowledge of how their behavioral and structural characteristics influence climate change adaptation policy is limited. This article provides an introduction to a collection of studies that seeks to explore the link between climate change adaptation and public bureaucracies, and to distill lessons for the scholarship on adaptation as well as the persistent debates on the role of administrative traditions in public policy. The articles in the special issue demonstrate that how state and social actors are organized, the ways in which scientific advice enters bureaucracies, and uniformity in the making and implementing of policy matter for adaptation policy. We conclude that the concept of administrative traditions is still necessary for understanding the choices made by public actors, but contend that other factors such as economic motives and political willingness should be considered more critically in the literature on administrative traditions.

    Indicators of resilience during the transition period in dairy cows : A case study
    Dixhoorn, I.D.E. van; Mol, R.M. de; Werf, J.T.N. van der; Mourik, S. van; Reenen, C.G. van - \ 2018
    Journal of Dairy Science 101 (2018)11. - ISSN 0022-0302 - p. 10271 - 10282.
    behavior - dairy cow - dynamic indicator - resilience - transition period
    The transition period is a demanding phase in the life of dairy cows. Metabolic and infectious disorders frequently occur in the first weeks after calving. To identify cows that are less able to cope with the transition period, physiologic or behavioral signals acquired with sensors might be useful. However, it is not yet clear which signals or combination of signals and which signal properties are most informative with respect to disease severity after calving. Sensor data on activity and behavior measurements as well as rumen and ear temperature data from 22 dairy cows were collected during a period starting 2 wk before expected parturition until 6 wk after parturition. During this period, the health status of each cow was clinically scored daily. A total deficit score (TDS) was calculated based on the clinical assessment, summarizing disease length and intensity for each cow. Different sensor data properties recorded during the period before calving as well as the period after calving were tested as a predictor for TDS using univariate analysis of covariance. To select the model with the best combination of signals and signal properties, we quantified the prediction accuracy for TDS in a multivariate model. Prediction accuracy for TDS increased when sensors were combined, using static and dynamic signal properties. Statistically, the most optimal linear combination of predictors consisted of average eating time, variance of daily ear temperature, and regularity of daily behavior patterns in the dry period. Our research indicates that a combination of static and dynamic sensor data properties could be used as indicators of cow resilience.
    Effects of early nutrition and transport of 1-day-old chickens on production performance and fear response
    Hollemans, M.S. ; Vries, S. de; Lammers, A. ; Clouard, C.M. - \ 2018
    Poultry Science 97 (2018)7. - ISSN 0032-5791 - p. 2534 - 2542.
    broiler - chicken - early nutrition - transport - behavior - production performance
    The importance of optimal early life conditions of broilers to sustain efficient and healthy production of broiler meat is increasingly recognized. Therefore, novel husbandry systems are developed, in which immediate provision of nutrition post hatch is combined with on-farm hatching. In these novel systems, 1-day-old-chick handling and transport are minimized. To study whether early nutrition and reduced transport are beneficial for broiler performance and behavior, the effects of early or delayed nutrition and post-hatch handling and transport were tested from hatch until 35 d of age, in a 2 × 2 factorial arrangement. In total, 960 eggs were hatched in 36 floor pens. After hatch, chicks were given immediate access to water and feed (early nutrition) or after 54 h (delayed nutrition). Eighteen hours after hatch, chicks remained in their pens (non-transported control), or were subjected to short-term handling and transport to simulate conventional procedures. Subsequently, chicks returned to their pens. Compared with delayed-fed chickens, early-fed chickens had greater body weight up to 21 d of age, but not at slaughter (35 d of age). No effects of transport or its interaction with moment of first nutrition were found on performance. At 3 d post hatch, transported, early-fed chicks had a greater latency to stand up in a tonic immobility test than transported, delayed-fed chicks, but only in chicks that were transported. At 30 d post hatch, however, latency was greater in transported, delayed-fed chickens than in transported, early-fed chicks. This may indicate long-term deleterious effects of delayed nutrition on fear response in transported chickens. It is concluded that early nutrition has mainly beneficial effects on performance during the first 2 wk post hatch, but these beneficial effects are less evident in later life. The combination of transport and early nutrition may influence the chicken's strategies to cope with stressful events in early and later life.
    Review of environmental enrichment for broiler chickens
    Riber, A.B. ; De Weerd, H.A. Van; Jong, I.C. De; Steenfeldt, S. - \ 2018
    Poultry Science 97 (2018)2. - ISSN 0032-5791 - p. 378 - 396.
    behavior - broiler - environmental enrichment - production system - welfare
    Welfare problems are commonly found in both conventional and organic production of broiler chickens. In order to reduce the extent of welfare problems, it has been suggested to provide stimulating, enriched environments. The aim of the present paper is to provide a review of the effect on behavior and welfare of the different kinds of environmental enrichments in the production of broilers that have been described in the scientific literature. Environmental enrichment is defined as an improvement of the environment of captive animals, which increases the behavioral opportunities of the animal and leads to improvements of the biological function. This definition has been broadened to include practical and economic aspects, as any enrichment strategy that adversely affects the health of animals or that has too many economic or practical constraints will never be implemented on commercial farms and thus never benefit animals. Environmental enrichment for broilers often has the purpose of satisfying behavioral needs and/or stimulating the broilers to an increased level of activity, which among others will reduce the occurrence of leg problems. Potentially successful environmental enrichments for broiler chickens are elevated resting-places, panels, barriers, and bales of straw ("point-source enrichment"), as well as covered verandas and outdoor ranges ("complex enriched environments"). Many of the ideas for environmental enrichment for broilers need to be further developed and studied, preferably in commercial trials, with respect to the use, the effect on behavior and on other welfare aspects such as leg health, and the interaction with genotype, production system, stocking density, light, and flock size. In addition, information on the practical application and the economics of the production system is often lacking, although it is important for application in practice.
    A Borrelia afzelii Infection Increases Larval Tick Burden on Myodes glareolus (Rodentia : Cricetidae) and Nymphal Body Weight of Ixodes ricinus (Acari: Ixodidae)
    Duijvendijk, Gilian van; Andel, Wouter van; Fonville, Manoj ; Gort, Gerrit ; Hovius, Joppe W. ; Sprong, Hein ; Takken, Willem - \ 2017
    Journal of Medical Entomology 54 (2017)2. - ISSN 0022-2585 - p. 422 - 428.
    behavior - Borrelia burgdorferi - Ixodes ricinus - manipulation - rodent
    Several microorganisms have been shown to manipulate their host or vector to enhance their own transmission. Here we examined whether an infection with Borrelia afzelii affects its transmission between its bank vole (Myodes glareolus, Schreber, 1780) host and tick vector. Captive-bred bank voles were inoculated with B. afzelii or control medium, after which host preference of Ixodes ricinus L. nymphs was determined in a Y-tube olfactometer. Thereafter, infected and uninfected bank voles were placed in a semifield arena containing questing larvae to measure larval tick attachment. Engorged larvae were collected from these bank voles, molted into nymphs, weighed, and analyzed for infection by PCR.Nymphs were attracted to the odors of a bank vole compared to ambient air and preferred the odors of an infected bank vole over that of an uninfected bank vole. In the semifield arena, infected male bank voles had greater larval tick burdens then uninfected males, while similar larval tick burdens were observed on females regardless of infection status. Nymphal ticks that acquired a B. afzelii infection had higher body weight than nymphs that did not acquire an infection regardless of the infection status of the vole. These results show that a B. afzelii infection in bank voles increases larval tick burden and that a B. afzelii infection in larvae increases nymphal body weight. This finding provides novel ecological insights into the enzootic cycle of B. afzelii.
    Gradual weaning during an extended lactation period improves performance and behavior of pigs raised in a multi-suckling system
    Nieuwamerongen, S.E. van; Soede, N.M. ; Peet-Schwering, C.M.C. van der; Kemp, B. ; Bolhuis, J.E. - \ 2017
    Applied Animal Behaviour Science 194 (2017). - ISSN 0168-1591 - p. 24 - 35.
    Multi-suckling system - get-away system - intermittent-suckling - gradual weaning - behavior - pigs
    We studied effects of two weaning procedures on the development of pigs raised in a multi-suckling (MS) system with five sows and their litters. One MS group was subjected to a gradual weaning treatment during a lactation period of 9 wk, which included forced intermittent-suckling (IS) for 10 h/d during the fifth wk of lactation, followed by a 4-wk period in which sows could voluntarily get away from their piglets (IS9 treatment). The other MS group was weaned abruptly at 4 wk of age and was subsequently housed in a nursery (A4 treatment). At 9 wk of age, pigs from both treatments were relocated to a finishing unit, where they were housed in a group of max. 35 pigs per treatment. Five consecutive batches of 10 sows and their litters were studied. Weaning had a more profound impact for the A4 pigs than IS and sow-initiated separation did for the IS9 pigs, demonstrated by a lower weight gain between d 27–33 (0.90 ± 0.08 vs. 1.51 ± 0.06 kg/pig, F1,4 = 25.23, p < 0.01), indications of a higher diarrhea occurrence, a distinct peak in belly-nosing behavior and numerically higher levels of aggression and damaging oral manipulation between wk 4–9. For IS9 pigs, weaning seemed to have less impact; feed intake after transition to the finishing unit was similar in both treatments, indicating that IS9 pigs had a more successful transition to a diet of only solid feed, and IS9 pigs showed no growth check, nor behavioral indicators of having difficulty coping with the post-weaning situation. The extended weaning process likely gradually prepared the gastro-intestinal tract to process solid feed, which may explain the better performance of the IS9 pigs. Additionally, benefits of the gradual weaning treatment were reflected in behavioral differences over the entire experiment; between 4–18 wk of age, IS9 pigs overall showed less belly-nosing, less damaging oral manipulation and had fewer lesions related with manipulation and aggression than A4 pigs. This may altogether indicate a less stressed state of the IS9 pigs. To conclude, IS9 pigs coped better with both transitions than A4 pigs did and the gradual weaning treatment had long-term beneficial effects, particularly concerning behavior. Therefore, gradual weaning in a multi-suckling system seems promising for improving piglet performance, behavior and welfare.
    DNA methylation and sex allocation in the parasitoid wasp Nasonia vitripennis
    Cook, N. ; Pannebakker, B.A. ; Tauber, E. ; Shuker, D.M. - \ 2015
    Wageningen UR
    behavior - evolution - reproductive - genetics - evolutionary - sex - allocation - ratio
    The role of epigenetics in the control and evolution of behavior is being increasingly recognized. Here we test whether DNA methylation influences patterns of adaptive sex allocation in the parasitoid wasp Nasonia vitripennis. Female N. vitripennis allocate offspring sex broadly in line with local mate competition (LMC) theory. However, recent theory has highlighted how genomic conflict may influence sex allocation under LMC, conflict that requires parent-of-origin information to be retained by alleles through some form of epigenetic signal. We manipulated whole-genome DNA methylation in N. vitripennis females using the hypomethylating agent 5-aza-2′-deoxycytidine. Across two replicated experiments, we show that disruption of DNA methylation does not ablate the facultative sex allocation response of females, as sex ratios still vary with cofoundress number as in the classical theory. However, sex ratios are generally shifted upward when DNA methylation is disrupted. Our data are consistent with predictions from genomic conflict over sex allocation theory and suggest that sex ratios may be closer to the optimum for maternally inherited alleles.
    Olfaction: An Overlooked Sensory Modality in Applied Ethology and Animal Welfare
    Nielsen, B.L. ; Jezierski, T. ; Bolhuis, J.E. ; Amo, L. ; Rosell, F. ; Oostindjer, M. ; Christensen, J.W. ; Mckeegan, D. ; Wells, D.L. ; Hepper, P. - \ 2015
    Frontiers in Veterinary Science 2 (2015)69. - ISSN 2297-1769
    odors - chemoreception - behavior - feeding - stress - housing - reproduction - disease
    Mating type and sexual fruiting body of Botrytis elliptica, the causal agent of fire blight in lily
    Terhem, R.B. ; Staats, M. ; Kan, J.A.L. van - \ 2015
    European Journal of Plant Pathology 142 (2015)3. - ISSN 0929-1873 - p. 615 - 624.
    cinerea - leaves - resistance - infection - behavior - system
    Botrytis elliptica is a necrotrophic pathogen that specifically infects Lilium species. Previous records show that B. elliptica collected in the field can successfully develop apothecia in vitro, however, there are no formal descriptions of apothecia of B. elliptica. The aim of this study was to analyse the sequence of the mating type loci of B. elliptica and produce apothecia in the laboratory in order to describe their morphology. The sequences of both MAT alleles (MAT1-1 or MAT1-2) of B. elliptica were determined and compared to the sister taxa, Botrytis cinerea and Sclerotinia sclerotiorum. Two strains of each mating type were used in crosses under controlled conditions to produce apothecia. Primordium rupture from sclerotial tissue occurred 74 days after fertilization and a mature apothecium formed within 1 month after rupture. The apothecia are 7 to 12 mm in height with a disk of 3 to 4 mm in diameter and 0.5 to 1 mm in thickness. The apothecial disk is usually umbilicate, depressed to funnel and rounded in shape. The number of apothecia growing on a sclerotium was one to nine. Asci are long, cylindrical with a size of 208¿×¿14 µm, thin walled and bearing eight ascospores. Ascospores are hyaline in colour, ellipsoidal with rounded ends, usually 18 to 24 µm in length and 6 to 10 µm in width (mean 19.5¿×¿8 µm). Ascospores were infectious on lily leaves.
    Exploiting the Spur of the Moment to Enhance Healthy Consumption: Verbal Prompting to Increase Fruit Choices in a Self-Service Restaurant
    Kleef, E. van; Broek, O. van den; Trijp, J.C.M. van - \ 2015
    Applied Psychology : Health and Well-Being 7 (2015)2. - ISSN 1758-0846 - p. 149 - 166.
    safety-belt use - field-experiment - vegetable intake - strategies - consumers - children - behavior - sales - risk
    Background: People often have good intentions to eat healthily, but these inten- tions may get overruled by temporary moments of temptation. The current study examined the effectiveness of “verbal prompting” as a nudge to increase fruit salad sales in a natural setting. Methods: A ¿eld experiment was conducted in a self- service restaurant during breakfast time. After an initial baseline period, the inter- vention involved four different prompts suggesting ordering a side dish (i.e. orange juice, fruit salad, pancakes) given by cashiers to visitors. The intervention phase lasted 13 weeks. Cash register and observational data were obtained. In addition, a sample of visitors (N = 393) responded to a survey. Results: A signi¿cant increase in sales of orange juice was observed during the orange juice verbal prompts intervention periods (35–42% of all breakfasts sold) compared to baseline (20% of all breakfasts sold). Similarly, sales of fruit salad (9%) and pancakes (3%) rose to a small but signi¿cant extent compared to baseline sales (3% and 1%, respectively). Survey results showed that customers did not feel pressurised into purchasing a side dish. Conclusion: Together, ¿ndings suggest that verbal prompts involving healthy side dishes are a potential useful nudge to implement in other food service settings. Keywords: choice architecture, fruit consumption, nudge, nudging, suggestive selling, verbal prompting
    Firms’ willingness to invest in a water fund to improve water-related ecosystem services in the Lake Naivasha basin, Kenya
    Mulatu, D.W. ; Oel, P.R. van; Veen, A. van der - \ 2015
    Water International 40 (2015)3. - ISSN 0250-8060 - p. 463 - 482.
    tropical forestry projects - environmental services - market actors - payments - management - behavior - private - choice - impact
    A valuation scenario was designed using a contingent-valuation approach and presented to decision makers in business firms in Kenya’s Lake Naivasha basin to test how applicable a water fund might be as a potential financing mechanism for a payment for water-related ecosystem services scheme. The findings indicate that measuring a firm’s willingness to invest in ecosystem services could help determine whether a firm would invest and engage with other stakeholders to pool their investments in ecosystem services. Linking the institutional decision-making behaviour of a firm and its willingness to invest in a water fund is the novelty of this article.
    Song trait similarity in great tits varies with social structure
    Snijders, L. ; Eijk, J.A.J. van der; Rooij, E.P. van; Goede, P. de; Oers, K. van; Naguib, M. - \ 2015
    PLoS ONE 10 (2015)2. - ISSN 1932-6203 - 14 p.
    parus-major - dawn chorus - bird song - honest advertisement - extrapair paternity - territory defense - neighbors - communication - behavior - songbirds
    For many animals, long-range signalling is essential to maintain contact with conspecifics. In territorial species, individuals often have to balance signalling towards unfamiliar potential competitors (to solely broadcast territory ownership) with signalling towards familiar immediate neighbours (to also maintain so-called “dear enemy” relations). Hence, to understand how signals evolve due to these multilevel relationships, it is important to understand how general signal traits vary in relation to the overall social environment. For many territorial songbirds dawn is a key signalling period, with several neighbouring individuals singing simultaneously without immediate conflict. In this study we tested whether sharing a territory boundary, rather than spatial proximity, is related to similarity in dawn song traits between territorial great tits (Parus major) in a wild personality-typed population. We collected a large dataset of automatized dawn song recordings from 72 unique male great tits, during the fertile period of their mate, and compared specific song traits between neighbours and non-neighbours. We show here that both song rate and start time of dawn song were repeatable song traits. Moreover, neighbours were significantly more dissimilar in song rate compared to non-neighbours, while there was no effect of proximity on song rate similarity. Additionally, similarity in start time of dawn song was unrelated to sharing a territory boundary, but birds were significantly more similar in start time of dawn song when they were breeding in close proximity of each other. We suggest that the dissimilarity in dawn song rate between neighbours is either the result of neighbouring great tits actively avoiding similar song rates to possibly prevent interference, or a passive consequence of territory settlement preferences relative to the types of neighbours. Neighbourhood structuring is therefore likely to be a relevant selection pressure shaping variation in territorial birdsong.
    Mosquito attraction: crucial role of carbon dioxide in formulation of a five-component blend of human-derived volatiles
    Loon, J.J.A. van; Smallegange, R.C. ; Bukovinszkine-Kiss, G. ; Jacobs, F. ; Rijk, M. de; Mukabana, W.R. ; Verhulst, N.O. ; Menger, D.J. ; Takken, W. - \ 2015
    Journal of Chemical Ecology 41 (2015)6. - ISSN 0098-0331 - p. 567 - 573.
    gambiae-sensu-stricto - ionotropic glutamate receptors - vector anopheles-gambiae - human skin microbiota - malaria mosquito - semifield conditions - aedes-aegypti - lactic-acid - behavior - culicidae
    Behavioral responses of the malaria mosquito Anopheles coluzzii (An. gambiae sensu stricto molecular 'M form') to an expanded blend of human-derived volatiles were assessed in a dual-port olfactometer. A previously documented attractive three-component blend consisting of NH3, (S)-lactic acid, and tetradecanoic acid served as the basis for expansion. Adding 4.5 % CO2 to the basic blend significantly enhanced its attractiveness. Expansion of the blend with four human-derived C4-volatiles was then assessed, both with and without CO2. Only when CO2 was offered simultaneously, did addition of a specific concentration of 3-methyl-1-butanol or 3-methyl-butanoic acid significantly enhance attraction. The functional group at the terminal C of the 3-methyl-substituted C4 compounds influenced behavioral effectiveness. In the absence of CO2, addition of three concentrations of butan-1-amine caused inhibition when added to the basic blend. In contrast, when CO2 was added, butan-1-amine added to the basic blend strongly enhanced attraction at all five concentrations tested, the lowest being 100,000 times diluted. The reversal of inhibition to attraction by adding CO2 is unique in the class Insecta. We subsequently augmented the three-component basic blend by adding both butan-1-amine and 3-methyl-1-butanol and optimizing their concentrations in the presence of CO2 in order to significantly enhance the attractiveness to An. coluzzii compared to the three- and four-component blends. This novel blend holds potential to enhance malaria vector control based on behavioral disruption.
    The power of regression to the mean: A social norm study revisited
    Verkooijen, K.T. ; Stok, F.M. ; Mollen, S. - \ 2015
    European Journal of Social Psychology 45 (2015)4. - ISSN 0046-2772 - p. 417 - 425.
    field-experiment - alcohol-use - implementation intentions - descriptive norms - injunctive norms - college-students - peer norms - behavior - drinking - interventions
    This research follows up on a study by Schultz et al. (2007), in which the effect of a social norm intervention on energy consumption was examined. The present studies included control groups to examine whether social norm effects would persist beyond regression to the mean. Both studies had a 2 (baseline consumption: below mean versus above mean)¿×¿2 (message condition: no-message control versus norm message) design. Based on baseline fruit (Study 1) or unhealthy snack (Study 2) consumption, students were classified as above mean or below mean for consumption. One week later, half of the students in the above-mean and below-mean groups received normative feedback; control groups did not. Neither study showed an effect of norm messages on behavior relative to control, providing evidence for regression to the mean as an alternative explanation. Findings highlight the importance of control groups to distinguish social norm intervention effects from mere regression to the mean.
    Social proof in the supermarket: Promoting healthy choices under low self-control conditions
    Salmon, S.J. ; Vet, E. de; Adriaanse, M.A. ; Fennis, B.M. ; Veltkamp, M. ; Ridder, D.T.D. de - \ 2015
    Food Quality and Preference 45 (2015). - ISSN 0950-3293 - p. 113 - 120.
    limited-resource account - ego depletion - physical-activity - decision-making - strength model - united-states - food choices - behavior - consumption - motivation
    Under low self-control conditions, people often favor tempting but unhealthy food products. Instead of fighting against low self-control to reduce unhealthy food choices, we aim to demonstrate in a field study that heuristic decision tendencies can be exploited under these conditions. To do so a healthy product was associated with a social proof heuristic, referring to the tendency to adopt the option preferred by others. A healthy low-fat cheese was promoted with banners stating it was the most sold cheese in that supermarket. A state of low self-control was experimentally induced in the supermarket, and compared to a high self-control condition. Participants low in self-control were more likely to buy the low-fat cheese, when this product was associated with the social proof heuristic, compared to when it was not. This suggests that under low self-control conditions, presenting social proof cues may benefit healthy purchases.
    What reported food-evoked emotions may add: A model to predict consumer food choice
    Gutjar, S. ; Dalenberg, J.R. ; Graaf, C. de; Wijk, R.A. de; Palascha, A. ; Renken, Remco J. ; Jager, G. - \ 2015
    Food Quality and Preference 45 (2015). - ISSN 0950-3293 - p. 140 - 148.
    consumption experience - responses - satisfaction - liking - taste - package - questionnaires - behavior - design - impact
    Food-evoked emotions provide information that goes beyond the information from traditional hedonic ratings. The objectives of our study were: (i) to investigate how intrinsic (sensory) and extrinsic (packaging) cues affect consumers’ emotional responses to foods, and (ii) to explore whether emotional responses to these cues combined with liking, predict actual food choice. Participants (n = 103) rated emotional responses to seven products under a blind taste, a package and a package and taste condition using the EsSense Profile™. During the blind taste condition participants also scored liking of the products. Test products were breakfast drinks and desserts. Food choice was measured in two different breakfast sessions reflecting a different choice context. In one choice context, products were presented blind to taste, after which participants chose one out of the seven foods to consume for breakfast. In the other choice context, participants based their choice on the package of the seven foods without tasting them. Results showed that emotions evoked by food products could be organised in a two-dimensional space, representing a valence (pleasantness) and an activation/arousal dimension. Specific emotional profiles generated for products differed across the blind taste, package and the package and taste condition, meaning that intrinsic and extrinsic product properties elicit in part different emotions. Liking and valence together had the strongest predictive value for product choice based on the product’s taste. The combination of liking, valence and arousal had the strongest predictive value for package-based choice. In conclusion, food-evoked emotions add predictive value to solely liking ratings, and may guide consumers’ product choice behaviour.
    Aqueous foams stabilized by chitin nanocrystals
    Tzoumaki, M. ; Karefyllakis, D. ; Moschakis, T. ; Biliaderis, C.G. ; Scholten, E. - \ 2015
    Soft Matter 11 (2015). - ISSN 1744-683X - p. 6245 - 6253.
    in-water emulsions - pickering emulsions - silica nanoparticles - polymer microrods - fluid interfaces - particles - cellulose - behavior - bubbles - microparticles
    The aim of the present study was to explore the potential use of chitin nanocrystals, as colloidal rod-like particles, to stabilize aqueous foams. Chitin nanocrystals (ChN) were prepared by acid hydrolysis of crude chitin and foams were generated mainly by sonicating the respective dispersions. The foamability of the chitin nanocrystals was evaluated and the resulting foams were assessed for their stability, in terms of foam volume reduction and serum release patterns, during storage. Additionally, the samples were studied with light scattering and optical microscopy in order to explore the bubble size distribution and morphology of the foam. Nanocrystal concentration and charge density was varied to alter the packing of the crystals at the interface. At low concentrations of ChNs, foams were stable against coalescence and disproportionation for a period of three hours, whereas at higher concentrations, the foams were stable for several days. The enhanced stability of foams prepared with ChNs, compared to surfactant-stabilized foams, can be mainly attributed to the irreversible adsorption of the ChNs at the air-water interface, thereby providing Pickering stabilization. Both foam volume and stability of the foam were increased with an increase in ChNs concentration, and at pH values around the chitin's pKa (pH 7.0). Under these conditions, the ChNs show minimal electrostatic repulsion and therefore a higher packing of the nanocrystals is promoted. Moreover, decreased electrostatic repulsion enhances network formation between the ChNs in the aqueous films, thereby providing additional stability by gel formation. Overall, ChNs were proven to be effective in stabilizing foams, and may be useful in the design of Pickering-stabilized food grade foams.
    Modification of Tetragnata montana (Araneae, Tetrafnathidae) web architecture induced by larva of the parasitoid Acrodactyla quadrisculpta (Hymenopteram Ichneumonidae, Polysphincta genus-group)
    Korenko, S. ; Korenkova, B. ; Satrapova, J. ; Hamouzova, K. ; Belgers, J.D.M. - \ 2015
    Zoological Studies 54 (2015). - ISSN 1021-5506
    host spiders - manipulation - pimplinae - araneidae - behavior
    Background: The polysphinctine wasp, Acrodactyla quadrisculpta, is a koinobiont ecto-parasitoid of spiders and is narrowly associated with the biology of its spider hosts. The larva, attached to the dorsal side of the abdomen, develops while the spider continues foraging. Shortly before pupation, the parasitoid larva manipulates the web-building activity of the host in order to construct a safe shelter against natural elements and predators during parasitoid pupation. Results: A. quadrisculpta was associated exclusively with the orb web weaving spiders Tetragnatha montana, with a parasitism incidence of 19%. The manipulated spider constructed a unique cocoon web that provided strong mechanical support for the parasitoid's pupal cocoon. The cocoon web consisted of one highly reinforced main thread, tensioned in 60% of cases by a reinforced side thread. The wasp cocoon, square in cross-section, was fastened along its length to the main cocoon thread. Conclusions: The wasp A. quadrisculpta was exclusively associated with an orb-weaving spider T. montana in the family Tetragnathidae. The alteration of the web architecture of T. montana induced by the larva A. quadrisculpta was unique and species specific.
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