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Sunday, May 19, 2019

The Secret Lives of Goats

Goats Galore (May 2019)


If you live in a drought-ridden, wildfire-prone area on the West Coast, you may see herds of goats chomping on dry grass and overgrown brush. This was initially surprising for many who live in urban areas, but it's become commonplace where I live. Announcements appear on local message boards, and families bring their children.


Goats Goats Goats (June 2017)


Goats are glamorous, and super popular on social media now (e.g. Instagram, more Instagram, and Twitter). Over 41 million people have watched Goats Yelling Like Humans - Super Cut Compilation on YouTube. We all know that goats have complex vocalizations, but very few of us know what they mean.





For the health and well-being of livestock, it's advantageous to understand the emotional states conveyed by vocalizations, postures, and other behaviors. A 2015 study measured the acoustic features of different goat calls, along with their associated behavioral and physiological responses. Twenty-two adult goats were put in four situations:
(1) control (neutral)
(2) anticipation of a food reward (positive)
(3) food-related frustration (negative)
(4) social isolation (negative)
Dr. Elodie Briefer and colleagues conducted the study at a goat sanctuary in Kent, UK (Buttercups Sanctuary for Goats). The caprine participants had lived at the sanctuary for at least two years and were fully habituated to humans. Heart rate and respiration were recorded as indicators of arousal, so this dimension of emotion could be considered separately from valence (positive/negative). For conditions #1-3, the goats were tested in pairs (adjacent pens) to avoid the stress of social isolation. They were habituated to the general set-up, to the Frustration and Isolation scenarios, and to the heart rate monitor before the actual experimental sessions, which were run on separate days. Additional details are presented in the first footnote.1





Audio A1. One call produced during a negative situation (food frustration), followed by a call produced during a positive situation (food reward) by the same goat (Briefer et al., 2015).


Behavioral responses during the scenarios were timed and scored; these included tail position, locomotion, rapid head movement, ear orientation, and number of calls. The investigators recorded the calls and produced spectograms that illustrated the frequencies of the vocal signals.



The call on the left (a) was emitted during food frustration (first call in Audio A1). The call on the right (b) was produced during food reward; it has a lower fundamental frequency (F0) and smaller frequency modulations. Modified from Fig. 2 (Briefer et al., 2015).


Both negative and positive food situations resulted in greater goat arousal (measured by heart rate) than the neutral control condition and the low arousal negative condition (social isolation). Behaviorally speaking, arousal and valence had different indicators:
During high arousal situations, goats displayed more head movements, moved more, had their ears pointed forwards more often and to the side less often, and produced more calls. ... In positive situations, as opposed to negative ones, goats had their ears oriented backwards less often and spent more time with the tail up.
Happy goats have their tails up, and do not point their ears backwards. I think I would need a lot more training to identify the range of goat emotions conveyed in my amateur video. At least I know not to stare at them, but next time I should read more about their reactions to human head and body postures.


Do goats show a left or right hemisphere advantage for vocal perception?

Now that the researchers have characterized the valence and arousal communicated by goat calls, another study asked whether goats show a left hemisphere or right hemisphere “preference” for the perception of different calls (Baciadonna et al., 2019). How is this measured, you ask?

Head-Turning in Goats and Babies

The head-turn preference paradigm is widely used in studies of speech perception in infants.

Figure from Prosody cues word order in 7-month-old bilingual infants (Gervain & Werker, 2013).




However, I don't know whether this paradigm is used to assess lateralization of speech perception in babies. In the animal literature, a similar head-orienting response is a standard experimental procedure. For now, we will have to accept the underlying assumption that orienting left or right may be an indicator of a contralateral hemispheric “preference” for that specific vocalization (i.e., orienting to the left side indicates a right hemisphere dominance, and vice versa).
The experimental procedure usually applied to test functional auditory asymmetries in response to vocalizations of conspecifics and heterospecifics is based on a major assumption (Teufel et al. 2007; Siniscalchi et al. 2008). It is assumed that when a sound is perceived simultaneously in both ears, the head orientation to either the left or right side is an indicator of the side of the hemisphere that is primarily involved in the response to the stimulus presented. There is strong evidence that this is the case in humans ... The assumption is also supported by the neuroanatomic evidence of the contralateral connection of the auditory pathways in the mammalian brain (Rogers and Andrew 2002; Ocklenburg et al. 2011).

The experimental set-up to test this in goats is shown below.



A feeding bowl (filled with a tasty mixture of dry pasta and hay) was fixed at the center of the arena opposite to the entrance. The speakers were positioned at a distance of 2 meters from the right and left side of the bowl and were aligned to it. 'X' indicates the position of the Experimenter. Modified from Fig. 2 (Baciadonna et al., 2019).


Four types of vocalizations were played over the speakers: food anticipation, food frustration, isolation, and dog bark (presumably a negative stimulus). Three examples of each vocalization were played, each from a different and unfamiliar goat (or dog).

The various theories of brain lateralization of emotion predicted different results. The right hemisphere model predicts right hemisphere dominance (head turn to the left) for high-arousal emotion regardless of valence (food anticipation, food frustration, dog barks). In contrast, the valence model predicts right hemisphere dominance for processing negative emotions (food frustration, isolation, dog barks), and left hemisphere dominance for positive emotions (food anticipation). The conspecific model predicts left hemisphere dominance for all goat calls (“familiar and non-threatening”) and right hemisphere dominance for dog barks. Finally, a general emotion model predicts right hemisphere dominance for all of the vocalizations, because they're all emotion-laden.

The results sort of supported the conspecific model (according to the authors), if we now accept that dog barks are actually “familiar and non-threatening” [if I understand correctly]. The head-orienting response did not differ significantly between the four vocalizations, and there was a slight bias for head orienting to the right (p=.046 vs. chance level), when collapsed across all stimulus types. 2

The time to resume feeding after hearing a vocalization (a measure of fear) didn't differ between goat calls and dog barks, so the authors concluded that “goats at our study site may have been habituated to dog barks and that they did not perceive dog barks as a serious threat.” However, if a Siberian Husky breaks free of its owner and runs around a fenced-in rent-a-goat herd, chaos may ensue.





Footnotes

1 Methodological details:
“(1) During the control situation, goats were left unmanipulated in a pen with hay (‘Control’). This situation did not elicit any calls, but allowed us to obtain baseline values for physiological and behavioural data. (2) The positive situation was the anticipation of an attractive food reward that the goats had been trained to receive during 3 days of habituation (‘Feeding’). (3) After goats had been tested with the Feeding situation, they were tested with a food frustration situation. This consisted of giving food to only one of the goats in the pair and not to the subject (‘Frustration’). (4) The second negative situation was brief isolation, out of sight from conspecifics behind a hedge. For this situation, goats were tested alone and not in a pair (‘Isolation’).”

2 The replication police will certainly go after such a marginal significance level, but I would like to see them organize a “Many Goats in Many Goat Sanctuaries” replication project.


References

Baciadonna L, Nawroth C, Briefer EF, McElligott AG. (2019). Perceptual lateralization of vocal stimuli in goats. Curr Zool. 65(1):67-74. [PDF]

Briefer EF, Tettamanti F, McElligott AG. (2015). Emotions in goats: mapping physiological, behavioural and vocal profiles. Animal Behaviour 99:131-43. [PDF]


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