Chapter 28 Paraphrasing 3. Checking Context

We’ve already seen the main features of a well-written paraphrasing statement. * The paraphrased sentence captures the key idea of the original paragraph. * The paraphrased sentence does not contain any directly quoted phrases longer than 2-3 words. If there ARE directly quoted words, they are terminology or descriptions of specific methods, not the authors original ideas. * The paraphrased version is not overly detailed. * The original source of the paraphrased information is provided.

We’ve also looked at how to find the citable facts in an article, and how to know when you should not use an article as a paraphrased source, and should go elsewhere.

For this exercise you are going to use all of the elements we explored previously again. We are adding a final element of paraphrasing: maintaining context.

Often when we paraphrase a source the goal is to capture specific information contained in a single line or a single section of the source article, and use that particular piece of information to support our own arguments. At other times we want to use part of the data from another study to support our own work. In these situations it is very hard to mis-represent the cited source’s intent.

Sometimes we want to cite a source to provide broader support for our own point of view. In these situations, we need to consider an entire section of a cited source, or even the entire article. The questions we want to ask are:

What are the 2-3 largest, most important arguments that the authors made?
Do their 2-3 main arguments support your argument or position?
Is there a reasonable, logical connection between their arguments and the general position or argument you want to support?

You do not want to pick out bits of others’ data and re-interpret them to suit you. Similarly you do not want to use statements made by other authors out of context. Scientists have a derogatory name for this practice: cherry picking.

Rather than summarizing ideas one paragraph at a time, your goals for this article are:

Identify the 3 most important points the authors are making in either the Introduction or the Discussion.
Look at the 3 statements at the top of the two sections, and based on what you identify as the most important points, decide which of the statements is best supported by this article.
For the statement you choose, write 1 sentence that paraphrases this article, and that you could put into a lab report.

Text Source

Landová E, Janovcová M, Štolhoferová I, Rádlová S, Frýdlová P, Sedláčková K, et al. (2021) Specificity of spiders among fear- and disgust-eliciting arthropods: Spiders are special, but phobics not so much. PLoS ONE 16(9): e0257726. https://doi.org/10.1371/journal.pone.0257726

Excerpt of the Original Introduction

Which general statement is best supported by this Introduction? What follow-up sentence could you add that summarizes this Introduction?

Humans perceive spiders as an imminent threat to human survival, even though few spiders are poisonous.
Humans are hard-wired by evolution to react negatively to spiders, though at least some of this behavior is learned.
Among organisms that humans innately fear, spiders seem to be unique, which suggests a deep evolutionary reason for such fear.

Evolutionary perspective offers an explanation why ancient biological stimuli that were threatening to our ancestors have been prioritised by our category-specific visual attention (animals [1], snakes [2], spiders [3], big cats [4], human faces [5]) and why these reactions are accompanied by strong emotions to this day [6]. The neuroscientists explore complex ways in which neural circuits are involved in connecting various areas responsible for attention, perceiving fear, and motor reaction [7, 8]. These circuits enable quick reaction to a specific life-threatening stimulus and is commonly known as the fear module [9, 10].

There is no doubt that throughout the evolutionary history, many animal species have been an important source of imminent threat to our survival either as predators [11], or parasites [12]. To this day, certain animals including spiders evoke high levels of fear and disgust (reviewed in [13]). In a survey using the standard Spider Phobia Questionnaire (SPQ), 10.3% out of 3 863 Czech respondents reported very high fear of spiders (scoring 22 or higher on 31-point scale; [13, 14]). Arachnophobia, an irrational, uncontrollable fear of spiders, is one of the most common specific animal phobias affecting 2.7–6.1% of general population, women significantly more often than men [15, 16]. These negative emotions associated with spiders are even more intriguing since only 0.5% of all spider species represent a real potential threat to humans [17].

Due to higher fear or even phobia of spiders being so prevalent in a general population, one could hypothesize its evolutionary roots. Spiders might have represented a real threat to our ancestors; thus, a rapid fear response would be highly adaptive. Subsequently, this specific fear of spiders (or similar invertebrates) or at least a predisposition for fast associative learning of fear response [18] would become genetically fixed through natural selection. This view is consistent with the idea of Seligman’s biological preparedness [19]. Should this be the case, we can hypothesize that people share this negative attitude across cultures, although Davey [20] attributed this phenomenon to shared cultural stereotype. Moreover, spiders evoke not only fear, but high level of disgust too [21]. Specifically, Lorenz et al. [22] found that aversion toward spiders is associated with pathogen disgust. Disgust originally evolved because it served as an effective mechanism for orally rejecting harmful substances without tasting them [23]. It allowed humans to avoid the ingestion of pathogens, too [24]. Related idea posits that, in human ancestors, disgust has increased avoidance of pathogens, parasites and possible sources of contamination [25]. Different possible ways of getting infection are important for this hypothesis: infection through skin or genitals contact with surfaces, ingestion of pathogens and parasites through contamination, and contact with diseases transmitting animals [20, 26]. These two evolutionary explanations of how spiders could have become emotionally salient stimuli are not mutually exclusive.

Several lines of evidence further point toward the evolutionary roots of negative emotions elicited by spider stimuli. Among those, the most serious one seems to come from developmental studies which support the view of the spiders as an important cognitive category already in infants [27–29], some as young as 5 month old [30]. However, indirect indications can be further named. One, as mentioned earlier, in self-reports, respondents typically state that spiders evoke equally fear as well as disgust [13, 31, 32]. This testifies to the widespread negative attitude toward spiders across respondents with different educational and socioeconomical background. While the negative attitude can be contributed to a learned culture stereotype, the only cross-cultural study we know of [33] reports on comparable attitudes in South African respondents. Two, in accordance with the preparedness hypothesis [19], respondents associate fear more readily with the spider stimuli than the neutral stimuli [10, 34] and such fear is less prone to extinction [35, 36]. Moreover, similar results are reported under the instructed extinction paradigm, which involves informing participants after the fear learning, that unconditional stimulus (electric shock) will no longer be present. This method facilitates extinction in fear irrelevant stimuli, however if the fear relevant stimuli were images of snakes and spiders, the fear was not sensitive to instructed extinction [37, reviewed in 38]. Nonetheless it was also shown that acquired fear inhibition can be modulated by participants’ sensitivity to fear of spiders [34] and lately, this line of argumentation has been questioned [39–41]. Three, respondents are attracted or distracted by spiders in visual attention tasks [42–44] suggesting spiders may be evolutionarily persistent threat specified for visual detection and attention capture. However, other papers show that the personal relevance of the spider stimuli is crucial [45] as well as its potential goal-relevance to the task [46]. While none of the indicators can be considered a conclusive evidence, cumulatively, they provide a reasonable argument for investigation of potential evolutionary roots of negative emotions associated with spiders.

Emotions can direct automatic attention to emotionally salient stimuli [47], such as spiders or snakes, and sometimes even precede conscious perception [48]. However, perception as a cognitive process of transformation of proximal stimulus into a percept (the accessible, subjective experience that is connected with activation of a certain category in the mind; [49]) modulates further late attention towards evolutionary relevant threatening stimuli [50]. Michalovski et al. [51] studied temporal dynamics of visual attention to the spiders using ERPs (event related potentials). They found that the spiders are processed preferentially in later stages of perceptual and evaluative processing, especially in spider phobics. Late cognitive stimulus evaluation, like its proper categorization, is thus important when we are confronted with classes of stimuli that have (or had in our evolutionary past) direct relevance for our well-being and survival than others. We can expect that extremely relevant stimuli are categorized into special emotional categories in human mind, which may differ from other categories [49], and they are preferentially processed in the brain [52, 53]. Forming the stimulus category in the mind is thus a cognitive process when people group certain objects or concepts as equivalent or analogous reducing the information complexity, but they acquire set of information thanks to association of the object with a certain category [54]. Proper categorization of the potentially life-threatening stimuli may still direct our late attention on the one hand, but may allow for effective regulation of the impact of negative emotions like fear or disgust on the other one [55]. Categorization of emotional stimuli as a cognitive process assumes the existence of categories based on the everyday experience or evolutionary past in some cases. If people with very different experiences form similar emotional categories containing life-threatening animal stimuli like scorpions as well as harmless spiders, it may indicate the existence of a pre-existing general category for these incentives in human mind, which may be generalized to a wider group of animal species. This argument supports the hypothetical existence of evolutionarily rooted negative emotions of specific animal stimuli, similarly to a more frequently used argument of the cross-cultural agreement in emotional evaluation of these stimuli [33].

Based on this, we hypothesise that some animal stimuli may form a specific category inside the human mind on the basis of shared morphological features perceived via our sensory system. Such cognitive category can additionally interact with emotional processing during its perception. Therefore, forming a cognitive category goes along with emotional evaluation, making it the cognitive process.

Are spiders therefore perceived as a specific group distinct from other invertebrates? Gerdes et al. [21] compared subjective emotional evaluation of spiders and three other groups of insects: beetles, bees and wasps, butterflies, and moths. They found that spiders evoke more fear and disgust than the other groups and they concluded that among these groups, spiders are truly specific stimuli. Contrary, Breuer et al. [56] found that all crawling invertebrates, spiders included, are perceived more negatively compared to those that can fly by 9–13 years old children. Shipley and Bixler [57] offered US college students 10 silhouettes of insects, spiders, and other invertebrates in paired forced choice test. In this study, spiders formed one cluster together with a praying mantis, wheel bug, stag beetle and a house centipede. Despite great attention paid to the study of fear and disgust evoked by spiders [13, 20, 32, 51, 58–61], the question of specificity of spider stimulus still remains open.

For these reasons, general aim of this study is to determine prototypical stimuli (spiders and spider-like arthropods) that elicit pronounced emotional response. We asked whether high negative emotional evaluation (fear and/or disgust) is specific to spiders compared to other arthropods. Regarding phylogeny, spiders are representatives of Chelicerata which in turn are one of four major extant arthropod groups (other three being Myriapoda, Crustacea and Insecta; for detailed phylogeny and taxonomy see [62], and S1 Table in S1 File). To answer our questions, we chose a wide variety of stimuli including several representatives of spiders, nine other main clades of chelicerates as well as representatives of above-mentioned arthropod groups. Together, the selected stimuli represent full morphological diversity of living spiders and its closest relatives allowing for a precise comparison on a very fine scale. Further, we asked which morphological features of spiders are responsible for their emotional evaluation. Because the emotional evaluation of spiders is closely related to the respondents’ sensitivity to a specific fear of spiders [13, 21], we tested people with normative as well as high fear of spiders. We focused on covering a full spectrum of respondents from those with low or no fear of spiders to suspected phobic and near phobic respondents. Relatively large numbers of diverse respondents are firstly crucial for validly defining spiders as a prototypical stimulus in a general population. Secondly, it allows investigating from what point specific fear of spiders affects subjective emotional evaluation of spider and spider-like stimuli in a manner a simple comparison of two extreme groups from opposite sides of the “fear spectrum” cannot.

Excerpt of the Original Discussion

Which of these general statements is best supported by the Discussion? What follow-up sentence could you add that summarizes this Discussion?

Spiders stimulate strong negative or even phobic reactions because they elicit both strong fear and strong disgust.
Negative responses to spiders have their evolutionary roots in the risk of venomous bites.
It is unlikely that negative responses to spiders have a simple explanation. There are likely multiple evolutionary roots and connections.

Is position of taxonomically defined spiders on fear and disgust scales distinctive compared to that of other chelicerates and arthropods?

When examining the mean ratings of stimuli, spiders ranked among the highest of all species according to both fear and disgust (see Table 1). All but four (out of 25) species of spiders ranked above average score of the stimuli altogether. Similarly, 18 spider species scored above average in disgust. Among the top ten highest ranked species according to fear, 7 were spiders. They were the southern black widow Latrodectus mactans (ranking at the very top), tarantula species of the genera Aptostichus, Macrothele, Theraphosa, and Aphonopelma, the strangely looking orb-weaver spider Micrathena schreibersi with extremely long spines serving for anti-predator defence [88], and the wolf spider Tasmanicosa leuckartii characteristic by its relatively large size. Three remaining species were arachnids highly resembling spiders in appearance–the whip spider Phrynus parvulus, camel spider Gluvia dorsalis, and the hooded tickspider Cryptocellus goodnighti. Although these three species might look dangerous, they are harmless to humans [89–91]. On the disgust scale, the situation was similar with Aptostichus, Macrothele, Gluvia, Tasmanicosa, Phrynus, Latrodectus, and Cryptocellus which all scored among the top ten. Second top ranked the centipede Ethmostigmus trigonopodus, sea-spider Ammothea hilgendorfi and the mite Trombidium holosericeum ranked at fifth and ninth place, respectively. A parasitic tick Ixodes pacificus scored quite low in disgust which was surprising as animals associated with dirt, decay, or disease (e.g., worms, lice, tapeworms, or cockroaches) usually trigger high disgust [13, 92]. In our previous study, an engorged tick and other parasites elicited stronger disgust than spider picture stimuli [93]. We hypothesize that either respondents did not recognize the stimulus (we used a starved tick in the current study), or multiple spider stimuli overshadowed the disgust elicited by a single tick.

When comparing mean fear and disgust ratings of the same stimulus, a clear pattern emerged. A vast majority of spiders scored higher in fear than in disgust, while the reverse was true for a vast majority of other chelicerates and arthropods (see Fig 2). An important exception was the striped bark scorpion (Centruroides vittatus), which scored very low in disgust but high in fear and hence had the highest difference between its fear and disgust ranking of all the examined stimuli. Parasites (the tick and the mite) scored much higher in disgust than fear, alongside with all centipedes, the millipede of the order Spirabolida, and the woodlouse Philoscia muscorum. To summarize, spiders elicit both strong fear and strong disgust. Further, fear elicited by spider stimuli is stronger than disgust elicited by the same stimulus. The reverse is true for other chelicerates and arthropods. While there are exceptions to these rules, it can be concluded that based on fear and disgust ratings, spiders (Araneae) are distinct stimuli among other examined invertebrates.

Do spiders form a single distinct cognitive category or more species of invertebrates are perceived as a “spider”?

Although spiders are distinctive in their fear and disgust rating among other invertebrates, it does not automatically mean that they form a single distinctive cognitive category. The grounds for categories may be determined by factors related to the perceiver (e.g., fear and disgust sensitivity of the respondents, negative experience with spiders, shared evolutionary past) as well as those features inherent to the stimulus (e.g., body plan with multiple legs, chelicerae, dangerously looking appendices, hairs, thorny protrusions). Theoretically, all invertebrate species that evoke fear or disgust of a certain level may be categorized together on the basis of emotional percept only, even though they are perceptually diverse (for a review, see [94]). However, this was not the case in our study.

Both cluster analysis and factor analysis divided stimuli into two major and well-defined groups that can be characterized as a “spider cluster” and “non-spider cluster”. Consistently, no matter the analysis (cluster or factor analysis) or evaluated emotion (fear or disgust), clusters were as follows. The spider cluster was formed by all but two spider species, together with the whip spider, camel spider, sea spider, hooded tickspider, and both harvestman species (Ortholasma levipes and Phalangium opilio). The non-spider cluster was formed by an earwig Forficula auricularia, a lousefly Crataerina pallida, the millipede, all centipedes, and all crustaceans together with the scorpion, a pseudoscorpion Roncus lubricus, the tick, and the mite. Although the position of a few species changed among clusters depending on the analysis or dataset, the overall pattern was very stable all-across (see Fig 3). To summarize, all chelicerates similar to spiders joined one category with them, while dissimilar morphotypes were excluded. This result is consistent with the view of inherited cognitive category of emotionally salient stimuli–“spiders”–which humans have shared on the basis of coevolution [44]. However, this category can be established on the basis of perceptual similarity as well [95].

To elucidate possible evolutionary roots of spider cognitive category, we confronted our results with developmental studies. Preschool children have enhanced visual detection of spiders over the mushrooms and cockroaches [27]. Further, 6-month-old children react to spiders (and snakes) by increased pupillary dilatation which indicates increased emotional reaction compared to their reaction to flowers and fishes [28]. Even 5-month-old infants have basic perceptual template for spiders as Rakison and Derringer [30] showed in a series of experiments with simplified schematic pictures of spiders. Scrambled schematic pictures did not work compared to ones with spider features in a biologically relevant position. These schematic simplified pictures of spiders were also generalized to real photographs of spiders in habituation experiment. As the infants did not have much experience with real spiders at this age, we can assume that 5-month-old infants have innate perceptual template for threatening biological spider-like stimuli. All these results support “spiders” as an inherited cognitive category shared by humans on the basis of coevolution.

Nevertheless, it should be stressed that “spiders” as a cognitive category are not identical with spiders in a biological (taxonomical) sense, i.e., with the order Araneae. The “spiders” as a category arising from the subjective emotional evaluation of diverse arthropod species is formed by stimuli’s morphological similarity to a typical spider morphotype that causes perceptual similarity for respondents. Morphologically similar chelicerates are considered spiders (e.g., the whip spider, the camel spider). Contrarily, some spiders far from a prototypical spider morphotype (e.g., the myrmecophilous genus Myrmaplata) can exceptionally be considered as non-spiders. In this sense, a “spider-like” cognitive category might be more convenient label. Lastly, not all spiders are alike. Two separate “spider-like” subcategories can be identified–(1) gracile, small-bodied, long-legged, smooth spiders and other chelicerates and (2) robust, large-bodied, hairy spiders roughly corresponding to tarantulas (Fig 3).

Which spider morphotypes are associated with high fear and/or disgust rating of the stimulus?

Analysis of chelicerate morphotypes provided same results when based on fear as well as disgust. Spider species were clearly placed alongside a gradient defined by body perimeter on one side and body area on the other. Therefore, one end represented gracile species with large perimeter but small area (e.g., a long-bodied cellar spider), and the other end robust species with large area and relatively small perimeter (e.g., various tarantula species). This further supported results discussed in previous section. Robust species proved as highly salient stimuli and were those scoring high in both fear and disgust. Larger body length and higher proportion of red colour were also associated with high fear and disgust score but were driven primarily by other chelicerate species, mainly the scorpion (of very elongated body) and the mite (of dark red colour).

There is only one group of truly dangerous spider species that could have been important in the evolutionary context–the black widows (genus Latrodectus, family Theridiidae). Black widows are distributed in multiple continents including Africa and the Middle East [17], the area critical for coevolution with humans, and therefore they could have been an important life-threatening stimulus to our ancestors. However, this spider genus is not robust at all. There are some robust venomous spiders that might be dangerous to humans. For example, the Australian funnel-web spiders (Atractidae) have a specific neurotoxin to deter marsupial, bird, and lizard predators, however its toxicity for humans is only a coincidence from the evolutionary point of view [96]. The same is true for tarantulas (Theraphosidae) as species dangerous to humans inhabit Southern America and Australia [97] and therefore are not relevant in the evolutionary context. Accordingly, it was the black widow which scored as the most fear-eliciting stimulus. For these reasons, tarantula species should not be viewed as a core prototypical spider stimulus but rather as a supernormal one [98].

Which characteristics of the respondents are predictors of fear and disgust rating of spiders and other arthropods?

Detailed analysis of the respondents’ characteristics revealed that self-reported negative personal attitude toward spiders, high score in SPQ, and high score in DS-R reflected in more negative rating of all stimuli, particularly spider stimuli. Women also rated all stimuli, although spiders in particular, more negatively than men. Older respondents as well as those with biological type of education rated all stimuli more positively. This held true for ratings in both fear and disgust (see Fig 4). Although these results are generally in line with results of other researchers (negative emotions elicited by spiders [21, 32, 58, 60, 99–101]; gender differences [102]), two interesting points can be discussed.

First, SPQ scores themselves predicted mean rating given to spider stimuli by a given respondent (app. 60% of explained variability for both fear and disgust). This was expected to a certain degree–Mertens et al. [103], for example, found that specific sensitivity to fear of spiders, not general anxiety, was responsible for effective fear conditioning of participants in virtual reality experiments. Still, it is worth mentioning the high predictive value of the sensitivity to a specific fear of spiders alone. In fact, factors like gender or biological type of education, which are sometimes emphasized as very important (reviewed in [33]), proved to be very much secondary to this sensitivity represented by a simple SPQ score. This result can be of interest to clinical practitioners and other researcher when assembling, for example, terrain research or pilot studies.

Second, SPQ rather than DS-R provided a better predictor in disgust ratings. This is consistent with Sawchuk et al. [59] who found that spider phobics responded more with fear than disgust toward spider stimuli. However, other studies emphasize the importance of disgust in spider phobia as well [61, 101]. We contribute our result to DS-R questionnaire covering a broad spectrum of disgust-related questions whereas SPQ focusing specifically on spider and spider-like stimuli. Although DS-R can be divided into three theoretically independent subscales–core disgust, animal reminder disgust, and contamination-based disgust [67]–none of these subscales provided a significantly better prediction than the overall score. Perhaps this can be attributed to a specific position of spiders that can be perceived somewhere between the animal reminder disgust and contamination-based disgust. Alternatively, the testament of explicit SPQ simply overshadowed still quite broad orientation of DS-R subscales. This conclusion is supported by our first point as well.

Is there a systematic difference in ratings of suspected phobic respondents compared to those with high, moderate, and low fear of spiders?

Owing to a relatively good sampling over the whole SPQ scale, we were able to define five categories that represented respondents with increasingly higher fear of spiders. We found that both fear and disgust mean scores of spider (Araneae) stimuli increased gradually with SPQ categories. This same, although less prominent trend was observed for other chelicerates and other arthropods. Although generally assumed, it was seldom shown on diverse groups of stimuli [21, 56] and/or respondents with diverse fear and disgust sensitivity [13, 14, 104].

When comparing different stimuli within the SPQ categories, other arthropods (insects, crustaceans, millipedes, and centipedes) were rated as eliciting the lowest fear by all SPQ categories. Accordingly, spiders and other chelicerates elicited higher fear in respondents of all SPQ categories. This result is crucial as it confirms our premise that spiders and spider-like chelicerates are more fear-eliciting than other groups of arthropods. To put it differently, spiders are a specific stimulus eliciting augmented fear in general population not just in people with high fear of spiders or in spider phobics. If this was not the case, the specificity of spiders could be doubted as a pathological deviation from standard (but see [105]). But according to our results, elevated fear of spiders compared to other arthropods is shared by all people in general, our work further points toward the evolutionary roots of negative emotions elicited by spider stimuli. To conclude, spiders are indeed special for everyone.

After validating the specificity of spider-like stimulus, we focused on differences between low fear and high fear respondents. Suspected phobic respondents scored insects, crustaceans, millipedes, and centipedes very similarly to respondents of almost all other categories (see Fig 5). In fact, if one category of respondents differed from the others, it would be respondents with extremely low fear of spiders. This was an important control confirming that high fear respondents were sensitive to specific fear of spiders, not general fear of all invertebrates or animals. Afterwards, we focused on spider and spider-like stimuli. In accordance with our expectations, suspected phobic respondents responded to them differently than respondents with low and extremely low fear of spiders. In behavioural tasks, similar results were previously reported for expectancy bias for encountering spiders [106], attentional bias to spider pictures [107], or stimulus-reaction task [108]. On the contrary, high fear respondents and suspected phobic respondents scored spider and spider-like stimuli very similarly (see Fig 5). In fact, exceptionally high correlations (95.3 and 92% of explained variability for fear and disgust, respectively) show that their scores were essentially the same. We confirmed that there was no difference in ratings of high fear and suspected phobic respondents (S15 Table in S1 File). Moreover, respondents with moderate fear (though their scoring was indeed somewhere in the middle) inclined more to the rating of the high fear and suspected phobic respondents than to that of low fear and extremely low fear respondents. Unexpectedly, it seems that the respondents with very low SPQ scores rather than suspected phobic ones deviate more from the average. To conclude, spiders are special but phobics not so much.

General Discussion

Our results show that spiders and spider-like chelicerates form a distinctive cognitive category but also that this category can be further split into two subcategories. The first one can be described as gracile spiders and spider-like chelicerates, the second as robust spiders. Since the robust spiders were generally the more frightening and disgusting stimuli, it could be argued that they form the core of the spider-like cognitive category. However, to the best of our knowledge, no spider species of this morphotype were relevant to human evolutionary history as a life-threatening stimulus. To our ancestors, only widow spiders of the genus Latrodectus could have posed a real threat. In this sense, a smaller, not so robust morphotype would have been a better candidate to evolve into a prototypical spider stimulus.

Throughout the whole work, analyses based on fear ratings and disgust ratings provided very similar results. However, one important exception needs to be discussed. For all SPQ categories of respondents, spider-like stimuli elicit more fear than other arthropods. However, this is not true for disgust. Extremely low fear respondents rate spider-like stimuli (as a whole category) as less disgusting than other arthropods. To specify, the spider-like cognitive category is stable for all respondents but its relation to other arthropods on the disgust scale is different for a substantial section of our sample. However, fear is universal. It is further a typical feature of the whole spider-like category that they trigger more fear than disgust (see Fig 2 and previous section of Discussion.). Based on these results, we can argue that high fear is specific for spider-like category while high disgust is generally elicited by all arthropods. Evolutionary roots of the specificity of the spider-like stimulus should therefore be sought in fear, with disgust being only secondary of these two emotions.

Disgust is an emotion that prepares us to avoid infection in various behavioural tasks such as pathogen avoidance, mate choice, and social interactions [109, 110]. The categories of disgust elicitors are hence variable–parasites, vectors of diseases, body fluids, body injuries, hygiene threats, some sexual practices, and immoral acts [23]. The broad function of disgust led to the evolution of complex system of perceptual, emotional, and cognitive mechanisms that enable us to infer the potential infection risk. The resulting behavioural and physiological response protects the body from potential infection. This complex psychological and behavioural network is known also as behavioural immune system (BIS) [111]. Spiders are neither parasites, neither important vectors of human diseases [112–114]. Nevertheless, we can find other examples of generalization of pathogen disgust. Parasitic invertebrates are rated all highly disgusting [13, 33] but the same is true for insects [22] and some other non-parasitic arthropods in our study. The grater generalization of high disgust-eliciting stimuli should be adaptive for the complex task (to avoid all possible sources of infection) since false negative should be less costly than false positive in the case of BIS.

Nevertheless, it was already shown that the spider-like stimulus is simply not a spider of the order Araneae (see previous section of Discussion). We hypothesized that spiders might have represented a real threat to our ancestors thus a rapid fear response or at least a predisposition for fast associative learning of fear response [18, 103, 115, but see 40] would be highly adaptive, become genetically fixed and become non-associative fear [44, 116–118]. Here, we suggest extending this hypothesis on some other chelicerate stimuli, some of which are actually more dangerous to humans than extant spider species. Such chelicerates are, of course, scorpions [119]. Similar idea was already explored [120]. However, the scorpion was very clearly not a member of spider-like cognitive category in this study. Still, only one scorpion stimulus was included and therefore its true relation to spider-like cognitive category could not have been inspected in detail. For now, we cannot conclude on this question.

The second line of this study focused on investigating the effect of sensitivity to a specific fear of spiders on the perception of spider and spider-like stimuli. Rather unconventionally, we studied this effect across the whole SPQ scores scale. We found that the high fear respondents scored stimuli identically to suspected phobic respondents. The minimum SPQ limit to classify a respondent into a “high fear” category (SPQ > 15) was defined on the basis of an independent sample of Czech respondents (N = 3863) and it corresponds to 4th quartile of SPQ scores assessed from that survey [13, 14]. That means that about 25% of general population can be used very reliably as an approximation to truly phobic respondents who are much less prevalent in the population and often not comfortable with participation in this type of research. We cannot stress enough how important this result is to future arachnophobia related research. It firstly significantly facilitates the recruitment of suitable respondents. In certain types of research, it secondly decreases a need for large samples of truly phobic respondents for whom such research may be emotionally demanding. We consider this the first of the two most important results of this study.

Multiple pieces of evidence can be named in support of evolutionary roots of negative emotions elicited by spider-like stimuli. They are the specificity of spiders among other invertebrates in general population (see previous section of Discussion), the high intensity of both fear and disgust they trigger [13, 31, 32], the existence of spider species which pose a real threat to humans [121], their association with pathogen disgust [20, 22], the results of visual attention tasks [42, 44], and the results of developmental studies [27–30]. Despite this fact, a simple and concise evolutionary explanation of negative emotions elicited by spider-like stimuli is difficult to formulate. We are aware that our study opens just as much questions as it answers. To further inspect possibility of evolutionary roots of spider-like cognitive category, we suggest addressing several issues in future research. First, all respondents in this work were Central Europeans, members of the so called WEIRD (Western, educated, industrial, rich, and democratic) society [122, 123]. Cross-cultural studies are needed to validate universality of discussed findings. Second, emotions elicited by live animals are rarely tested, yet live animals are the ultimate stimuli for evolution. In addition, animals’ body size or motion are important characteristics of the stimuli [124] and therefore a study examining emotions elicited by live invertebrates is further needed. Third, although the spider-like cognitive category was relatively well explored in this work, other categories of fear- or disgust-eliciting invertebrates were not. A detailed comparison to other prominent groups of such invertebrates (e.g., scorpions) could shed more light into the research of animal phobias. Nonetheless, we consider the delineation of spider-like cognitive category the second of the two most important results of this study.