It is widely believed that exposure to sweetened foods and beverages stimulates the liking and desire for sweetness. Here we provide an updated review of the empirical evidence from human research examining whether exposure to sweet foods or beverages influences subsequent general liking for sweetness (‘sweet tooth’), based on the conclusions of existing systematic reviews and more recent research identified from a structured search of literature. Prior reviews have concluded that the evidence for a relationship between sweet taste exposure and measures of sweet taste liking is equivocal, and more recent primary research generally does not support the view that exposure drives increased liking for sweetness, in adults or children. In intervention trials using a range of designs, acute exposure to sweetness usually has the opposite effect (reducing subsequent liking and desire for sweet taste), while sustained exposures have no significant effects or inconsistent effects. Recent longitudinal observational studies in infants and children also report no significant associations between exposures to sweet foods and beverages with measures of sweet taste preferences. Overall, while it is widely assumed that exposure to sweetness stimulates a greater liking and desire for sweetness, this is not borne out by the balance of empirical evidence. While new research may provide a more robust evidence base, there are also a number of methodological, biological and behavioural considerations that may underpin the apparent absence of a positive relationship between sweetness exposure and liking.

In Preference, Value, Choice, and Welfare, I argued, among other things, that preferences in economics are and ought to be total subjective comparative evaluations, that the theory of rational choice is a reformulation of everyday folk-psychological explanations and predictions of behaviour, and that revealed preference theory is completely untenable. All three of these theses have been challenged in essays by Erik Angner (2018), Francesco Guala (2019) and Johanna Thoma (2021a, 2021b). This essay responds to these criticisms and defends these three theses.

One of the most common harmful mites in edible fungi is Histiostoma feroniarum Dufour (Acaridida: Histiostomatidae), a fungivorous astigmatid mite that feeds on hyphae and fruiting bodies, thereby transmitting pathogens. This study examined the effects of seven constant temperatures and 10 types of mushrooms on the growth and development of H. feroniarum, as well as its host preference. Developmental time for the total immature stages was significantly affected by the type of mushroom species, ranging from 4.3 ± 0.4 days (reared on Pleurotus eryngii var. tuoliensis Mou at 28°C) to 17.1 ± 2.3 days (reared on Auricularia polytricha Sacc. at 19°C). The temperature was a major factor in the formation of facultative heteromorphic deutonymphs (hypopi). The mite entered the hypopus stage when the temperature dropped to 16°C or rose above 31°C. The growth and development of this mite were significantly influenced by the type of species and variety of mushrooms. Moreover, the fungivorous astigmatid mite preferred to feed on the ‘Wuxiang No. 1’ strain of Lentinula edodes (Berk.) Pegler and the ‘Gaowenxiu’ strain of P. pulmonarius (Fr.) Quél., with a shorter development period compared with that of feeding on other strains. These results therefore quantify the effect of host type and temperature on fungivorous astigmatid mite growth and development rates, and provide a reference for applying mushroom cultivar resistance to biological pest control.

The aim of this study was to assess the extent to which three non-invasive measures of welfare in laying hens (egg-shell quality, corticosteroid levels as measured from the birds' faeces, and behavioural preferences) were correlated over a period of five days in two groups of birds. One group had access to an enriched test area (bark chips on the floor and a tray of sprouted wheat); the other group had access to a comparably sized barren area (bare wire mesh floor). The measure of preference used was the amount of time hens spent in the test area as measured each day. It was predicted that birds with access to the less preferred environment would show higher levels of faecal corticosteroids and egg-shell anomalies. However, although the birds showed a preference for the enriched environment from Day 1, the other two measures did not follow the same pattern. Faecal corticosteroid metabolites showed an initial increase in both groups, which declined significantly by Day 4, with the ‘enriched’ birds in fact showing a trend for higher levels than the ‘barren’ birds. Shell thickness also showed a change over the five days, but with a different time course: declining to a minimal level on Day 3 and then rising again by Day 5. No measure of shell quality was significantly different between the two environments, but there was a trend for changes in shell thickness to be more pronounced in eggs from enriched birds. The results indicate the caution that needs to be exercised in using shell quality or corticosteroid measurements in isolation from assessments of what the animals themselves prefer.

The preferences of growing pigs for substrates were investigated by giving small groups of pigs a choice between two substrates in each test. The seven substrates examined were concrete, mushroom compost (spent), peat, sand, sawdust, straw and woodbark. Thirteen comparisons of pairs of substrates were tested with four replicates of each comparison. Eleven-week-old pigs (in groups of six) were placed in specially designed choice pens where they had access to two different substrates. The pigs were allowed to habituate to the pen for 1 week and at the end of week 2 the substrates were swapped. In weeks 2 and 3 the time spent by the pigs in each substrate was recorded. Peat, mushroom compost and sawdust were preferred most, with sand next and woodbark and straw being preferred only to concrete. It is suggested that growing pigs may be attracted to substrates which are similar in texture to earth.

Rather than construct lists of many different welfare indicators and give each of them the same weight, I argue that the assessment of animal welfare should be directed at answering two key questions: I) Are the animals healthy? 2) Do they have what they want? Behaviour has a major role in answering both. Behaviour is currently used to help answer the first question through its use in the clinical and pre-clinical assessment of pain, injury and disease, and potentially could have an even greater role, particularly if used in conjunction with new technology. Behaviour is also of crucial importance in gauging what animals want, most obviously in the use of choice and preference tests, but also through other methods that are particularly suitable for on-farm welfare assessment. These include quantitative observations of the spatial distribution of animals and of behavioural ‘indicators’ of what animals want, such as vocalisations.

Six pairs of steers were allowed to choose between two types of floors in a paired choice test. The four floors tested were a fully slatted floor, a fully slatted floor covered with rubber mats, a solid floor with sawdust bedding, and a solid floor with straw bedding. All combinations of floor types were tested and the choices were repeated eight times, using naïve animals. The animals were allowed 17 days to habituate, and on days 18-21 their behaviour was recorded by video for 72 hours. Straw was the most preferred floor type, followed by sawdust, then mats, and finally slats. During a second test period, rubber mats were compared with rubber strips, and no significant preferences were found.

Choice tests are commonly used to measure animals’ preferences, and the results of such tests are used to make recommendations regarding animal husbandry. An implicit assumption underlying the majority of choice tests is that the preferences obtained are independent of the set of options available in the test. This follows from two assumptions about the mechanisms of choice: first, that animals use absolute evaluation mechanisms to assign value to options, and second, that the probability of choosing an option is proportional to the ratio between the value of that option and the sum of the values of the other options available. However, if either of these assumptions is incorrect then preferences can differ depending on the composition of the choice set. In support of this concern, evidence from foraging animals shows that preferences can change when a third, less preferred option is added to a binary choice. These findings have implications for the design and interpretation of choice tests.

The motivation of juvenile rabbits to graze was tested by offering a choice of coarse mix or grass as rewards to rabbits fed a nutritionally adequate diet of carrots and hay. Before measuring the motivation of the 16 rabbits, eight were offered access to grass for 16 days and the remaining eight were kept in outdoor hutches. An initial preference test was then conducted using a Y-maze apparatus, in which the rabbits were offered a choice of grass or coarse mix for 3 min. The rabbits that had not previously been offered grass had a strong preference for the grass reward, whereas those that had chose coarse mix and grass equally. Measurement of rabbits’ behaviour during the reward period revealed that rabbits spent longer eating if their reward was grass; this difference was particularly notable toward the end of the 3 min period. If they received a coarse mix reward, they spent more of the 3 min self-grooming, standing still and chewing the wire of the cage. Feeding rabbits with a coarse mix diet may therefore increase the likelihood of problem behaviours including inactivity and trichophagia. The rabbits were also trained in a novel operant test of motivation for the two rewards, in which they were required to circumnavigate an object several times before receiving a reward. The number of circumnavigations before a reward was offered was progressively increased, and rabbits were offered two opportunities to take the reward at each level. Although the rabbits were prepared to circumnavigate the object up to II times on average, there was little evidence that they would work harder for a grass reward than for a coarse mix reward. This may have been because they had previously had experience of grass during the preference tests. It is concluded that juvenile rabbits show a strong initial preference for a grass reward, compared with coarse mix, but that this preference disappears after brief exposure to grass. There was no strong evidence that rabbits will work harder to receive a grass reward than to receive a coarse mix reward.

Metabolic cages are used for housing rats and mice for up to five days for collection of urine and/or faeces. The small, barren area of the metabolic cage compromises animal welfare as the animals lack a solid floor, shelter, nest material and social contact. We constructed and tested a practically-applicable enrichment device designed to meet behavioural needs for environmental complexity. The influence of this device on the cage preferences and stress levels of the animals was evaluated. A box-shaped enrichment device was designed and implemented in existing metabolic cages. Male Tac:SD rats were housed for five days in an enriched metabolic cage (EMC; n = 12) or a standard metabolic cage (SMC; n = 12), and data were collected on bodyweight, food and water intake, urination and defaecation, as well as urinary corticosterone and creatinine. Moreover, open-field behaviour and cage preferences were assessed. Rats in both groups gained significantly less weight when housed in metabolic cages. Furthermore, SMC rats failed to increase their weight gain after being housed in the metabolic cage. Defaecation was significantly higher in the SMC than in the EMC and so was urinary creatinine. No group differences were found in open-field behaviour. However, in comparing activity before and after housing in the metabolic cage, only SMC animals exhibited significantly lower total activity. In a preference test, a preference for the tunnel connecting the cages in the preference test and a side preference for the left side were found. This side preference was eliminated when the EMC was placed on the right side, whereas the right side was significantly avoided when the EMC was placed on the left side. Based on these results, we conclude that, to some extent, the enrichment device improved the welfare of rats housed in EMC, compared to those in SMC.

Commercially reared broiler chickens are commonly supplied with drinking water through lines of nipple drinkers that are positioned above the birds' heads to avoid water leaking and spoiling the litter underfoot. This means that the birds have to peck upwards to obtain water, an action that is very different from the ‘scoop’ action of natural drinking seen when birds drink from troughs or puddles. In this study we investigate the welfare implications of this unnatural drinking behaviour imposed by nipple drinkers. We show 1) that chickens have no apparent aversion to the taste of tap water, 2) that they prefer bell drinkers and troughs over nipple drinkers, 3) that the stereotyped ‘scoop’ action is seen even when birds are drinking from bowls of different heights, 4) that chickens have a strong preference for drinking from nipples that are lower rather than higher and, 5) that when offered a choice between bowls and nipples of the same height, the chickens are indifferent to the method of water presentation. We conclude that the height at which water is presented to chickens is more important to them than whether they can drink with the natural ‘scoop’ action. While this might suggest that chicken welfare could be improved by lowering the drinker lines, wet litter causes welfare issues of its own through its effect on hock burn and pododermatitis. We suggest that drinker systems should be designed so that both aspects of welfare (birds able to drink in their preferred way and clean litter) are possible.

A number of alternative farrowing systems have recently been developed, some of which have been more successful at improving welfare and productivity than others. It is argued that for a system to be successful it should meet with the behavioural requirements of the sow at this time. A number of studies have been carried out to observe the natural behaviour patterns of the peri-parturient sow in a wide range of environmental conditions. These studies have shown that during each phase of peri-parturient behaviour there are a number of key environmental features and conditions which are important to the sow. These include the social environment, shelter, nesting material and offspring interaction. This information can be useful in the design of farrowing systems. A review of the literature indicated that the more these conditions are met, the more readily the sow can adapt to the system, leading to improvements in maternal behaviour and piglet production.

The provision of foraging opportunities may be a simple way of improving an animal's welfare, but this approach has been neglected for laboratory rats (Rattus norvegicus). Standard housing contains little enrichment, and food is often provided ad libitum, which may result in inactivity and obesity, especially in mature males. Foraging enrichments may offer a way to correct these deficiencies. This study compared three potential enrichments — a limited-access hopper, gnawing sticks and a foraging device — to standard housing and feeding conditions, in order to examine their effects on rat body weight, food consumption, behaviour and preferences. The subjects were 12 mature male Wistar rats. Effects were assessed from daily weighing and from video records of the rats' behaviour over 24 h periods. The rats' preferences were determined using a four-way test system in which they could choose between a standard cage and cages offering the three potential enrichments. Compared to the standard housing and feeding, the limited-access hopper had a tendency to reduce food consumption, but the time spent feeding increased. The gnawing sticks provided the rats with the opportunity to gnaw, but did not affect other behaviours or body weight. The foraging device had the benefits of reducing aggression and allowing the rats to search for and manipulate food, but resulted in significant gains in body weight. Additionally, the foraging device was the preferred feeding source. Of the four possible feeding locations, the rats spent the least amount of time in the standard cage. The foraging device provided the most benefits but requires further modification to address problems of obesity.

Most American respondents give “irrational,” magical responses in a variety of situations that exemplify the sympathetic magical laws of similarity and contagion. In most of these cases, respondents are aware that their responses (usually rejections, as of fudge crafted to look like dog feces, or a food touched by a sterilized, dead cockroach) are not “scientifically” justified, but they are willing to avow them. We interpret this, in some sense, as “heart over head.” We report in this study that American adults and undergraduates are substantially less likely to acknowledge magical effects when the judgments involve money (amount willing to pay to avoid an “unpleasant” magical contact) than they are when using preference or rating measures. We conclude that in “head-heart” conflicts of this type, money tips the balance towards the former, or, in other words, that money makes the mind less magical.

Understanding how sustainable preference change can be achieved is of both scientific and practical importance. Recent work shows that merely responding or not responding to objects during go/no-go training can influence preferences for these objects right after the training, when people choose with a time limit. Here we examined whether and how such immediate preference change in fast choices can affect choices without time limit one week later. In two preregistered experiments, participants responded to go food items and withheld responses toward no-go food items during a go/no-go training. Immediately after the training, they made consumption choices for half of the items (with a time limit in Experiment 1; without time limit in Experiment 2). One week later, participants chose again (without time limit in both experiments). Half of the choices had been presented immediately after the training (repeated choices), while the other half had not (new choices). Participants preferred go over no-go items both immediately after the training and one week later. Furthermore, the effect was observed for both repeated and new choices after one week, revealing a direct effect of mere (non)responses on preferences one week later. Exploratory analyses revealed that the effect after one week is related to the memory of stimulus-response contingencies immediately after the training, and this memory is impaired by making choices. These findings show mere action versus inaction can directly induce preference change that lasts for at least one week, and memory of stimulus-response contingencies may play a crucial role in this effect.