Simple SummaryGood animal welfare requires minimizing suffering and promoting positive experiences. To achieve this, we need reliable indicators of animals’ psychological states. In humans, different moods and emotions (“affects”) are associated with changes in visual attention (“attention bias”). We review studies investigating whether attention biases are also indicators of affect in animals. Although research is limited, evidence for affect-driven attention biases has been found in several species, especially primates and livestock. These studies are discussed in relation to tasks developed for measuring attention in humans. We identify additional findings from human psychology that might be applied to animals, particularly species not studied before, and conclude that affect-driven attention bias is a promising welfare indicator. However, it may be more useful for studying responses to specific stimuli, rather than general wellbeing. With further study, we hope these findings contribute to fulfilling society’s ethical obligations towards animals.AbstractAttention bias describes the differential allocation of attention towards one stimulus compared to others. In humans, this bias can be mediated by the observer’s affective state and is implicated in the onset and maintenance of affective disorders such as anxiety. Affect-driven attention biases (ADABs) have also been identified in a few other species. Here, we review the literature on ADABs in animals and discuss their utility as welfare indicators. Despite a limited research effort, several studies have found that negative affective states modulate attention to negative (i.e., threatening) cues. ADABs influenced by positive-valence states have also been documented in animals. We discuss methods for measuring ADAB and conclude that looking time, dot-probe, and emotional spatial cueing paradigms are particularly promising. Research is needed to test them with a wider range of species, investigate attentional scope as an indicator of affect, and explore the possible causative role of attention biases in determining animal wellbeing. Finally, we argue that ADABs might not be best-utilized as indicators of general valence, but instead to reveal specific emotions, motivations, aversions, and preferences. Paying attention to the human literature could facilitate these advances.

Barren housing and high stocking densities may contribute to negative affective states in broiler chickens, reducing their welfare. We investigated the effects of environmental complexity and stocking density on broilers’ attention bias (measure of anxiety) and tonic immobility (measure of fear). In Experiment 1, individual birds were tested for attention bias (n = 60) and in Experiment 2, groups of three birds were tested (n = 144). Tonic immobility testing was performed on days 12 and 26 (n = 36) in Experiment 1, and on day 19 (n = 72) in Experiment 2. In Experiment 1, no differences were observed in the attention bias test. In Experiment 2, birds from high-complexity pens began feeding faster and more birds resumed feeding than from low-complexity pens following playback of an alarm call, suggesting that birds housed in the complex environment were less anxious. Furthermore, birds housed in high-density or high-complexity pens had shorter tonic immobility durations on day 12 compared to day 26 in Experiment 1. In Experiment 2, birds from high-density pens had shorter tonic immobility durations than birds housed in low-density pens, which is contrary to expectations. Our results suggest that birds at 3 weeks of age were less fearful under high stocking density conditions than low density conditions. In addition, results indicated that the complex environment improved welfare of broilers through reduced anxiety.

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ABSTRACT. The typical V‐shaped pattern of biting activity that Glossina morsitans show in nature has been assumed to be due to environmental control (especially by temperature), but is now known also to be under control from an endogenous circadian clock. The relative importance of these two components was investigated (a) under constant conditions in actographs, and (b) by a re‐analysis of published field data. The actograph study reveals: (1) the length of flight bursts is the same at all phases of the rhythm; (2) the shape of the circadian V‐pattern changes with its amplitude, so that the less active a fly is, the more of its activity it performs in the morning; (3) both arms of the V respond to dawn as their principal zeitgeber; (4) high (35°C) and low (19°C) constant temperature reduce spontaneous activity level by c. 80%, and depress the evening arm of the V disproportionately. The analysis of the field data reveals: (1) the V occurs in nature independently of temperature; (2) biting activity is correlated positively with temperature in the morning and evening, but negatively through the middle of the day; (3) light directly influences the daily rhythm mainly by its effects at low intensity (the ‘photonegative reaction’ being a response to high temperature); (4) humidity has little influence on activity level. It is concluded that roughly 80% of the amplitude of the V‐pattern in the field is due to endogenous circadian control, and only 20% to direct control by temperature.