In this section, as a last step in our argument, we will evaluate some of the human practices involving animals in light of the considerations we have made. Due to space constraints, we can just give a rough idea of the relevance of our theoretical claims for the field of applied animal ethics and human–animal interactions. Moreover, we are only going to consider those animals that are under direct human care, even though Nussbaum hints at the possibility that the capabilities approach may give rise to certain duties towards wild animals (see Nussbaum 2007, 374ff.). Throughout this section, we will often refer to certain practices that we consider ethically questionable as a whole (like the raising of animals for food), but we will assess them only with respect to the noxious effect they may have upon the moral subjecthood of the animals involved. There are many further ethical concerns with respect to these practices that are well known and have been widely discussed in the literature, but we will proceed by bracketing them and focusing on the issue at hand. This is not meant as a way of lessening the importance of these ethical concerns. Rather, our ultimate aim is to contribute a new aspect to the ethical debate surrounding these practices and perhaps strengthen the case against certain ones.

Until now, we have refrained from referring to real animals and instead used hypothetical constructs to illustrate our point. In what follows, we will refer to actual animal species whose moral capabilities have only recently begun to be studied (if at all). While we still lack the sort of evidence to confidently attribute moral capacities to them, we will proceed by assuming that they are moral subjects, in order to identify potential harms that we may be inadvertently inflicting on them. As we saw, an animal can have her moral capabilities thwarted (1) if she is precluded from the possibility of exercising them, or (2) if her moral capabilities are taken away from her. We shall now consider how these two forms of thwarting may occur in everyday human-animal interactions. For ease of exposition, we are going to divide the (1)-type cases into two groups, and consider those that are analogous to Sustitia 2 ’s—because they involve animals witnessing the distress of their conspecifics and being physically prevented from intervening—separately from other (1)-type cases in which animals are deprived of further necessary pre-conditions for their moral capabilities to be exercised. We will thus refer to practices that involve humans (a) preventing animals from intervening in response to a conspecific in distress (section “Practices That Involve Animals Witnessing the Distress of Conspecifics”), (b) depriving animals from further pre-conditions for their moral capabilities to be exercised (section “Practices That Deprive Animals of Other Pre-Conditions for the Exercise of Their Moral Capabilities”), and (c) eliminating the animals’ ability to act morally (section “Practices That Eliminate the Moral Capabilities of Animals”).

Practices That Involve Animals Witnessing the Distress of Conspecifics

Even though Sustitia 2 was an imaginary example, her life conditions may not differ much from those of real animals who are raised for food. As we have already pointed out, painful and distressing procedures in farm animal husbandry are abundant, and indeed, ethical concerns with respect to the methods involved in breeding, raising, handling, transporting, and slaughtering farm animals have been raised for decades (e.g. Rollin 2003). Due to the overcrowding that characterises intensive farming, these painful procedures will often take place while in the presence of conspecifics. This, however, is an issue that has received comparatively little attention. Only rather recently has it begun to be systematically addressed as a research topic. For instance, it is currently debated whether pigs and other animals brought to slaughter suffer from witnessing their conspecifics’ pain and fear (Anil et al. 1996, 1997; Düpjan et al. 2011; Edgar et al. 2012; Reimert et al. 2013). As usual, the focus of these studies has been the welfare problems involved in these situations. The possibility remains, however, that these animals may be moral subjects, and that, upon witnessing their conspecifics’ distress, they experience an urge to engage in caring behaviour that they cannot fulfil due to the presence of physical barriers. As we have already explained, this might add a new dimension to the ways in which these animals are being harmed.

Farm animals are not the only class of animals under human care that are often exposed to the distress of conspecifics. Lab animals, too, will frequently find themselves in similar situations. The procedures involved in experimental set-ups include handling the subjects, collecting blood samples, performing orogastric gavage (a technique used to administer nutrients directly to the stomach via an oral tube) (Balcombe et al. 2004), restraining their movements, performing tail-vein injections, and euthanising them (Sharp et al. 2003; Boivin et al. 2016), all of which frequently cause pain or distress to the subjects. Other animals in the laboratory may have perceptual access to these processes and will most likely be prevented from interfering. We already have a significant amount of evidence suggesting that rodents undergo emotional contagion when in the presence of a conspecific in distress (Knapska et al. 2006; Langford et al. 2006; Jeon et al. 2010; Atsak et al. 2011; Burkett et al. 2016), and that, when given the choice, they will help or engage in affiliative behaviour directed at a distressed individual (Church 1959; Rice and Gainer 1962; Evans and Braud 1969; Greene 1969; Langford et al. 2010; Bartal et al. 2011, 2014; Burkett et al. 2016). Therefore, in this context it is also important to consider whether the animals are having their moral capabilities thwarted.

Practices That Deprive Animals of Other Pre-Conditions for the Exercise of Their Moral Capabilities

The exercise of an animal’s moral capabilities will most likely depend on the existence of a stable social environment where relationships with conspecifics can take place, develop, and be maintained. The existence of such a stable social environment can thus be plausibly considered as an important pre-condition for the flourishing of an animal’s moral capabilities. Many husbandry systems resort to the re-grouping, separation, or even isolation of animals, thus depriving them of this pre-condition, and potentially thwarting their moral capabilities.

This sort of unstable social environment is very common in farms. Farm animals are grouped and re-grouped according to productivity and reproductive state. This could constitute a problem, for instance, for dairy cows, who are gregarious animals and develop complex social relationships, characterised by feeding and resting together, or by engaging in allogrooming. Gutmann et al. (2015) showed that long-term familiarity had a stronger effect on the intensity of social relationships, measured in terms of time and energy investment, than having a very recent shared experience. They conclude that it is actually long-term familiarity that creates preferred social partners in dairy cows. But if farm animals are frequently re-grouped, the only social relationships possible, then, might be short-term relationships. They lose their preferred social partners, and this may hinder the flourishing of their moral capabilities, for evidence suggests that animals have a higher probability of engaging in caring and helping behaviour when they are familiar with the other subject (Cronin 2012; Bartal et al. 2014).

Routine re-grouping is not the only procedure that causes an inadequate social environment for the flourishing of farm animals’ moral capabilities. Several of the housing conditions found in factory farms, such as sow stalls and farrowing crates, have been severely criticised, amongst other things, because they result in an enforced isolation from conspecifics (see e.g. Rollin 2011, especially chapter 15). The thwarting of the moral capabilities of these isolated animals adds a new dimension to the welfare problems that such housing methods cause.

Other animals under human care are also deprived of the stable social environment that would be a pre-condition for exercising their moral capabilities. Zoo animals are often separated from each other due to space constraints (if families become too big), and rehoused to other zoos because of breeding programs. Lab animals might be kept in sterile, single housing due to the requirements of a controlled experimental setting. And even if some legislation tries to put a stop to it, companion animals are often kept in isolation from conspecifics, even highly social animals, like parrots, which has been shown to have harming effects (Aydinonat et al. 2014). Furthermore, companion animals kept in shelters, such as dogs, might very often experience the breaking up of social relationships when individuals of their group are rehomed. In this light, the common practice of rescuing dogs from the streets may not be as innocuous as is usually considered, as these animals lose their familiar environment and very likely all their well-known partners. They might be brought to a foster home with no other companion dog around them—a situation that could possibly mean fewer opportunities for their moral capabilities to be exercised.

In sum, if the animals in these different examples are subjects with complex social lives that include moral lives, then re-grouping, separating, and isolating them may disrupt or preclude the appearance of those bonds that are a pre-condition for the exercise of their moral capabilities.

Practices That Eliminate the Moral Capabilities of Animals

In the practices that we have considered until now, the animals involved are, to a bigger or lesser extent, prevented from exercising their moral capabilities. In this final section, we will consider human practices that go over and beyond this, by altogether eliminating the animals’ capability to behave morally.

Some human–animal interactions involve breeding, training, conditioning, or modifying the animals with the aim of eliminating some (or all) of their moral capabilities. The most obvious example here is that of fighting animals. Indeed, the training (and also breedingFootnote 21) that fighting dogs undergo aims precisely at enhancing their aggressiveness and eliminating any potential caring response to a conspecific in distress (Kalof and Iliopoulou 2011). Cattle used for bullfighting are also selectively bred to enhance aggressiveness (Silva et al. 2006; Correia et al. 2015), as are the chickens used for cock fighting (Guo et al. 2016).

But it is probably in the lab where the elimination of animals’ moral capabilities has been performed in the most intentional and methodical manner. Indeed, several psychologists have undertaken this as a research project. Perhaps the most paradigmatic example is Harry Harlow and his experiments on maternal separation, dependency needs, and social deprivation (for an overview on Harlow’s research see Harlow 1958; Harlow et al. 1965; Blum 2004). Harlow raised rhesus monkeys from birth onward in bare wire cages, facing partial or total maternal deprivation. He would offer them the choice between two inanimate surrogate mothers: one made of cloth and the other of wire. The infants were found to insistently seek the cloth mothers, even when they were designed to shake them, stab them with blunt spikes, or push them away via a mechanical flap. These monkeys “never experienced mother love, nor any other kind of monkey affection,” and when they themselves were impregnated and had their own offspring, they “either completely ignored or abused” their babies, or in many cases killed them (Harlow and Suomi 1971, 1535). By subjecting monkeys to this treatment, as well as to total isolation chambers, Harlow systematically created individuals who were completely “deficient in social play and sexual behavior,” as well as “hyperaggressive in peer interaction” (Arling and Harlow 1967, 371).

Harlow’s experiments, as shocking as they sound, should not be considered an isolated event in psychology. During the past 30 years, on-going maternal deprivation experiments, conducted for example at the NIH in the US, have subjected hundreds of infant macaques to similar conditions as Harlow’s experiments. They are heavily criticised from a bioethical perspective for being both unnecessary and cruel (Novak 2014; Medical Research Modernization Committee 2017). The potential elimination of the monkeys’ moral capabilities is another factor to consider in the ethical assessment of these tests.

Further examples of experiments performed with the aim of interfering in the animals’ moral capabilities include Tulogdi et al. (2014), who subjected rats to post-weaning social isolation, thereby inducing deficits in pro-social behaviour. These deficits were eliminated by resocialisation during adulthood, but the rats’ abnormal aggressiveness remained resilient to this treatment. Hernandez-Lallement et al. (2016) have also induced deficits in pro-social behaviour in rats by performing surgery aimed at damaging the amygdala (brain area responsible for emotion and affiliation). They plan to continue their research along these lines in order to produce “an animal model of callousness,” for which “[r]odents offer a cheap, convenient and ethically less controversial alternative to non-human primates” (Hernandez-Lallement et al. 2018). Our argument helps to shed some light on the ethical problems that are, in fact, involved in such experiments.