Only participants that completed the animal pictures evaluation task were retained for analyses (N = 517). A preliminary data analysis showed evidence of systematic responding (i.e., same value of the response scales used in 80% of the ratings), which lead to the exclusion of eight participants (final sample = 509). Results reported a small percentage of outliers (1.33%—identified considering the criterion of 2.50 SDs above or below the mean evaluation of each stimulus in a given dimension). Therefore, no further responses were excluded.
3.1. Frequency Distribution
We computed means, standard deviations and confidence intervals for each image on each dimension (see
Supplementary Data). Based on the confidence interval, images were categorized as low, moderate or high on each dimension. Animal images were categorized as moderate when the confidence interval included the response scale midpoint of 4.00; as low when the upper bound of the confidence interval was below the scale midpoint; and as high when the lower bound of the confidence interval was above the scale midpoint (for similar procedure, see References [
4,
11,
70].
Figure 2 represents the frequency distribution of animal images, rated low, moderate and high, on each of the 11 rated dimensions (i.e., valence, arousal, etc.). In the text below, we also provide some examples of animals that fell within each grouping (low, moderate, high).
As shown in
Figure 2, most animals were rated as positive (58%, e.g., dolphin, penguin), as familiar (62%, e.g., cat, rabbit) and as having high capacity to feel (57%, e.g., gorilla, dolphin). A smaller percentage was categorized as negative (18%, e.g., mosquito, fly) or with moderate valence (24%, e.g., cricket, squid), low on familiarity (8%, e.g., leech, krill) or as moderately familiar (30%, e.g., frog, shrimp) and has having lower (10%, e.g., clam, sea snail) or moderate capacity to feel (33%, e.g., scorpion, seahorse). Furthermore, most animals were rated as low on the remaining dimensions, namely similarity to humans (84%, e.g., sea snail, fly), dangerousness (74%, e.g., clam, snail), edibility (70%, e.g., fly, mosquito, koala), acceptability to kill for human consumption (73%, lion, dog). A small percentage was perceived as highly (3%, e.g., gorilla, chimp) or moderately (13%, e.g., elephant, horse) similar to humans, highly (14%, e.g., tiger, crocodile) or moderately dangerous (12%, e.g., kangaroo, panda), highly (18%, e.g., sardine, sea bass) or moderately (13%, e.g., rabbit, guppy) edible and highly (15%, e.g., codfish, lobster) or moderately (13%, e.g., goose, squid) acceptable to kill for human consumption.
In the remaining dimensions, the images were distributed across the three levels. For example, ratings for the cuteness dimension show that animals were judged as low (43%, e.g., fly, cockroach) or high (43%, e.g., dolphin, cat) on this dimension, with a smaller percentage of animals categorized a moderately cute (14%, e.g., seagull, cow). Most animals received high feelings of care (44%, e.g., cat, dolphin), with similar distributions across low (33%, e.g., mosquito, fly) and a smaller percentage rated as moderate (23%, e.g., turkey, frog) on feelings of care. Concerning capacity to think, animals were evenly categorized across low (42%, sea snail, mussel, clam), moderate (25%, e.g., swan, chameleon) and high capacities (33%, dolphin, chimp). Moreover, most animals received moderate arousal scores (43%, e.g., ladybug, pig), with similar distributions across low (31%, e.g., sea snail, woodlouse) and high arousal (26%, e.g., lion, cat).
3.3. Differences in Ratings: Individual Characteristics
Table 3 presents a summary of the mean evaluations across dimensions, for the entire sample and separately by gender. Overall, participants evaluated the animal images above the scale midpoint in valence, familiarity, feelings of care and capacity to feel, all
p-values ≤ 0.004 and below the scale midpoint in the remaining measures, all
p-values ≤ 0.043. Mean ratings for cuteness,
p = 0.609 and capacity to think,
p = 0.583, did not differ significantly from scale midpoint.
3.3.1. Gender
Differences according to participants’ gender in these overall evaluations were only found for a few dimensions. As shown in
Table 3, women (vs. men) evaluated the animals as more familiar,
t(507) = −2.11,
p = 0.035, Cohen’s
d = 0.18, more capable to feel,
t(507) = −2.78,
p = 0.006, Cohen’s
d = 0.24, less edible,
t(454.229) = 6.17,
p < 0.001, Cohen’s
d = 0.55 and less acceptable to kill for human consumption,
t(444.681) = 5.47,
p < 0.001, Cohen’s
d = 0.50.
3.3.2. Age
Overall, animal ratings did not differ much according to participants’ age. However, results showed that age correlated with valence, r = 0.15, p = 0.001, cuteness, r = 0.13, p = 0.003 and feelings of care ratings, r = 0.11, p = 0.014. Specifically, the older the participant, the higher were the valence, cuteness and feelings of care ratings of animals.
3.3.3. Diet
To examine the impact of dietary habits on animal evaluation we recoded the type of diet reported by the participant according to the meat ingestion: omnivores (i.e., people who included meat in their diets in an unrestricted manner; 81.4%), restricted omnivores (i.e., pescatarian and flexitarian diets; 11.4%) and meat avoiders (i.e., vegetarians or vegans; 7.2%). As expected, results showed significant mean differences on most of the ratings, except familiarity, as a function of diet (see
Table 4). Step-wise differences generally emerged, with the largest mean differences observed between omnivores and meat avoiders, with values for restricted omnivores generally falling between the two. Meat avoiders evaluated animals higher on valence, arousal, cuteness, similarity to humans, capacity to feel, capacity to think, feelings of care and with lower edibility and acceptability to kill, in comparison with omnivores and meat reducers, all
p-values ≤ 0.022,
ηp2 = 0.03 to 0.09. Meat avoiders also evaluated animals as less dangerous than omnivores,
p < 0.001,
ηp2 = 0.03. Furthermore, compared to omnivores, meat reducers evaluated animals as less acceptable to kill for human consumption,
p < 0.001,
ηp2 = 0.09 and displayed higher feelings of care for them,
p = 0.022,
ηp2 = 0.09.
3.3.4. Living Area
Overall, animal ratings did not differ much according to participants’ living area. The only exception was for ratings of animals’ capacity to feel, r = 0.09, p = 0.057, with marginally greater attributed capacity to feel to animals among those participants from urban areas.
3.3.5. Companion Animal Ownership
Results showed differences between participants who currently had a companion animal and participants who had not in animal ratings. Particularly, participants who reported currently owning (vs. not owning) a companion animal rated animals higher in the following dimensions: valence,
t(313.558) = −2.37,
p = 0.019, Cohen’s
d = 0.22, arousal,
t(506) = −2.79,
p = 0.031, Cohen’s
d = 0.28, cuteness,
t(506) = −3.10,
p = 0.002, Cohen’s
d = 0.31, feelings of care,
t(506) = −3.38,
p = 0.001, Cohen’s
d = 0.34, capacity to feel,
t(282.615) = −2.81,
p = 0.005, Cohen’s
d = 0.27, capacity to think,
t(308.101) = −3.51,
p = 0.001, Cohen’s
d = 0.33. Moreover, those who currently had a companion animal also rated animals lower in dangerousness,
t(506) = 2.90,
p = 0.004, Cohen’s
d = 0.28, edibility,
t(506) = 2.57,
p = 0.011, Cohen’s
d = 0.25 and acceptability to kill for human consumption,
t(506) = 2.84,
p = 0.005, Cohen’s
d = 0.28 (see
Table 5).
Similarly, results also showed differences in animal ratings between participants who had a companion animal during childhood and participants who had not. Particularly, participants who reported to own a companion animal during childhood rated animals higher in the following dimensions: valence,
t(506) = −2.32,
p = 0.021, Cohen’s
d = 0.33, arousal,
t(506) = −2.61,
p = 0.009, Cohen’s
d = 0.35, cuteness,
t(506) = −3.03,
p = 0.003, Cohen’s
d = 0.43, feelings of care,
t(506) = −2.96,
p = 0.003, Cohen’s
d = 0.40 and capacity to think,
t(506) = −2.28,
p = 0.023, Cohen’s
d = 0.30 (see
Table 6).
3.4. Differences in Ratings: Animals’ Biological Categories
We categorized the animal images according to their biological category and compared mean ratings across each category (see
Figure 1), using a repeated measures ANOVA for each evaluative dimension (with Huynh-Feldt correction as sphericity assumption was not verified). Based on post hoc comparisons with Bonferroni correction, we identified categories with the highest and lowest score in each dimension (see
Table 7).
Overall, ratings were highly affected by animal categories in all dimensions (all
p-values < 0.001, 0.34 < η
p2 < 0.75; see
Table 7). Mammals were rated as the most positive animal category (all other comparisons with mammals,
p-values < 0.001). Arachnids were the most negative category, though the means were not significantly different in comparison to clitellates (all other comparisons with arachnids,
p-values ≤ 0.003). Mammals were also the most arousing category and clitellates were rated as the least arousing category, all
p-values < 0.001. Likewise, mammals were rated the most familiar category and clitellates were the least familiar category, all
p-values ≤ 0.001. The same pattern was observed for cuteness, such that mammals were rated as the cutest category, all
p-values < 0.001; and clitellates were the least cute, though not significantly less cute than arachnids and bivalves, all
p-values ≥ 0.628 (all other comparisons with clitellates,
p-values ≤ 0.001). Expectedly, mammals were the category rated as more similar to humans from all the categories, all
p-values < 0.001. Bivalves were the category with lowest similarity to humans.
Arachnids were rated the most dangerous animal category, all p-values < 0.001. Bivalves were rated the least dangerous, along with gastropods (all other comparisons with bivalves and gastropods, all p-values ≤ 0.001). Bivalves were the most edible category, though not significantly more edible than cephalopods, fish and malacostrans (all other comparisons with bivalves, p-values ≤ 0.033). Clitellates were the category with the lowest edibility.
Mammals were attributed, by far, the highest capacity to think (all comparisons with mammals, p-values < 0.001) and the highest capacity to feel, all p-values < 0.001. The lowest thinking capacity was attributed to bivalves, clitellates, gastropods, insects and malacostrans. The lowest capacity to feel was attributed to bivalves and clitellates, all p-values ≤ 0.037. Bivalves were rated the most acceptable category to kill for human consumption, though not significantly more acceptable to kill than cephalopods, fish, gastropods and malacostrans, p-values ≥ 0.331 (all other comparisons with bivalves, p-values < 0.001). Amphibians were rated the least acceptable to kill for human consumption. Finally, mammals were the category that elicited the highest feelings of care and protection, all p-values < 0.001. Arachnids received the lowest feelings of care and protection, along with bivalves and clitellates (all other comparisons with bivalves, all p-values ≤ 0.016).
3.5. Evaluative Dimensions Predicting Moral Attitudes towards Animals
Two multiple linear regression were conducted to predict our two moral outcome variables: (1) acceptability to kill form human consumption and (2) feelings of care and protection. Using the raw correlations to guide us, the following predictor variables were included in the model because they correlated to a significant degree with at least one of the outcome variables: familiarity, cuteness, dangerousness, edibility, similarity to humans, capacity to feel and capacity to think. Multicollinearity analysis showed no concerns on this assumption (Tolerance = 0.45 to 0.92, Variance Inflation Factor = 1.09 to 2.24).
For acceptability to kill form human consumption, results showed a significant regression equation, F(7,501) = 175.37, p < 0.001, with the predictor variables explaining 71.0% of acceptability to kill for human consumption. Familiarity (β = 0.054), cuteness (β = −0.110), edibility (β = 0.813) and capacity to feel (β = −0.072) contributed at statistically significant levels to the prediction of acceptability to kill, all p-values ≤ 0.045. The remaining variables did not statistically contribute to the model (β ≤ −0.046), all p-values ≥ 0.196. Regarding feelings of care and protection, results also showed a significant regression equation, F(7,501) = 88.32, p < 0.001, with the predictor variables explaining 55.2% of feelings of care and protection. Similar to the first model, cuteness (β = 0.602), edibility (β = −0.087) and capacity to feel (β = 0.082) made statistically significant contributions to the prediction of feelings of care, all p-values ≤ 0.050. The remaining variables did not significantly contribute to the model (β ≤ 0.083), all p-values ≥ 0.063.