Spiders at the Cocktail Party: An Ancestral Threat that Surmounts

35 Pages·2014·0.73 MB·English

by  Joshua J. New

(cid:0)(cid:2)(cid:2)(cid:3)(cid:4)(cid:5)(cid:3)(cid:6) (cid:7)(cid:8)(cid:9)(cid:10)(cid:11)(cid:2)(cid:12)(cid:13)(cid:4)(cid:5)
Spiders at the Cocktail Party: An Ancestral Threat that Surmounts Inatten-
tionalBlindness
JoshuaJ.New,TamsinC.German
PII: S1090-5138(14)00103-2
DOI: doi: 10.1016/j.evolhumbehav.2014.08.004
Reference: ENS5935
Toappearin: EvolutionandHumanBehavior
Receiveddate: 12April2014
Reviseddate: 23July2014
Accepteddate: 6August2014
Pleasecite this article as: New, J.J. & German,T.C., Spiders at the CocktailParty: An
Ancestral Threatthat Surmounts Inattentional Blindness, EvolutionandHumanBehavior
(2014), doi: 10.1016/j.evolhumbehav.2014.08.004
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Running Head: SPIDERS AT THE COCKTAIL PARTY 1
Spiders at the Cocktail Party: An Ancestral Threat that Surmounts Inattentional Blindness

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Joshua J New1
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Tamsin C German2
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Word counts:
Main text 5798

Title 12 D
Figure Captions 129
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Abstract 171
References 2076 T

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1 Department of Psychology, Barnard College, Columbia University
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2 Department of PsAychology, University of California, Santa Barbara

* Corresponding author: Joshua New, Department of Psychology, Barnard College, 3009
Broadway, 10027. E-mail address: [email protected]
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Abstract
The human visual system may retain ancestral mechanisms uniquely dedicated to the rapid
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detection of immediate and specific threats (e.g. spiders and snakes) that persistently recurred
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throughout evolutionary time. We hypothesized that one such ancestral hazard, spiders,
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should be inherently prioritized for visual attention and awareness irrespective of their visual or
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personal salience. This hypothesis was tested using the iSnattentional blindness paradigm in
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which an unexpected and peripheral stimulus is presented coincidentally with a central task-
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relevant display. Despite their highly marginalized presentation, iconic spiders were
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nonetheless detected, localized, and identified by a very large proportion of observers.

Observers were considerably less likely Dto perceive 1) different configurations of the same
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visual features which diverged from a spider prototype, or “template”, 2) a modern threatening
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stimulus (hypodermic needle) comparable in emotional salience, or 3) a different fear-
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irrelevant animal (housefly). Spiders may be one of a very few evolutionarily-persistent threats
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that are inherently specified for visual detection and uniquely “prepared” to capture attention
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and awareness irreAspective of any foreknowledge, personal importance, or task-relevance.

Keywords: Attentional capture, fears, inattentional blindness, biological preparedness
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SPIDERS AT THE COCKTAIL PARTY 3

Spiders at the Cocktail Party: An Ancestral Threat that
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Surmounts Inattentional Blindness
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1. Introduction
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In our daily, modern life, the ability to maintain focused attention to tasks despite
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numerous potential distractions is a highly desirable abiliSty. However, critical events may
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require an interruption of our focused attention despite their irrelevance to any exigent goals
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and expectations (Most, Scholl, Clifford, & Simons, 2005). Such critical events can be physical
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and non-conceptual. For instance, looming objects provoke automatic responses for avoiding

bodily injury such as reflexive orienting D(Franconeri & Simons, 2003), defensive eye blinks
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(Yonas, 1981), and avoidant head jerks (Yonas et al., 1977). Another large class of important
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events is of a learned, conceptual, and personal nature. In the famous “cocktail party” effect,
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for example, our name said aloud in a neighboring conversation strongly commands our
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attention (Wood & Cowan, 1995). We propose that the visual system may be inherently
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prepared to orientA attention to a third class of events – specific types of objects that have been
of recurring and immediate importance over evolutionary time (Coss & Goldthwaite, 1995;
New, Cosmides, & Tooby, 2007; Tooby & Cosmides, 1990).
Emotional disorder researchers have long-debated whether the high frequency of fears
and phobias for ecological threats such as snakes and spiders reflect a “biological
preparedness” for detecting and surviving the persistently recurring hazards of our ancestral
environments (Marks & Nesse, 1994; Öhman & Mineka, 2001; Seligman, 1971). Some of the
most directly studied examples of this kind are angry faces (e.g. Öhman, Lundqvist, & Esteves,
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2001), snakes (e.g. Öhman & Mineka, 2003), and spiders (Öhman, Flykt, & Esteves, 2001b), each
of which have been advanced as model instances of biologically prepared fears.
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Human faces, though, are at least as important in modern society as they have been in
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ancestral environments, which complicates the attribution of their attentional capture to
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ontogenetic or phylogenetic causes. Spiders, on the other hand, rarely constitute a serious
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physical threat to people today. Only about 200 of the aSpproximately 40,000 extant spider
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species pose serious medical concerns to healthy adults by envenomating bites (Diaz, 2004).
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Medically confirmed fatalities are extremely rare – around six annually in the U.S. (Langley,
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2005) and less than 200 annually worldwide (Russell, 1991).

Yet, the spider genus, LatrodectuDs (the widow spiders), present a particularly illustrative
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case for the commonly held – but rarely examined – assumption that spiders were a persistent
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and potentially injurious feature of humans’ ancestral environments. Species of Latrodectus
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are now found on every continent (except Antarctica), however, there is a particularly high
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density of species in southern Africa were they likely originated (Garb, González, & Gillespie,
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2004). Although tAhere is little or no fossil evidence of Latrodectus, amber fossil specimens of
its closest sister genus, Steatoda (Arnedo, Coddington, Agnarsson, & Gillespie, 2004), have been
dated to the mid-Eocene epoch (48.6 – 40.4 million years ago; Berland, 1939; Petrunkevitch,
1942). For comparison, an ancient predatory threat to primates, snakes, evolved envenomating
bites by 60 million years ago (Vidal, 2002). Their continuous coexistence with the catarrhine
species (Old World monkeys and apes) may have compelled profound evolutionary changes to
those primate species’ perceptual systems in order to detect snakes pre-attentively – rather
than evolve a venom resistance like other mammals (Isbell, 2006; Le et al., 2013).
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Unfortunately, comparative and paleobiological evidence is not likely to uncover when – or the
first ancestral species in which – a behaviorally identifiable snake or spider “detector” might
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have first arose (but see Isbell, 2006 for review).
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Although there are still far more snake bites and fatalities (Kasturiratne et al., 2008), the
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effects of widow spider bite envenomation, termed latrodectism, are considered to be the most
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medically important spider bite syndrome worldwide (GrSaudins et al., 2012). Widow spider
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venom contains a phylogenetically unique and extremely potent neurotoxin, α-latrotoxin,
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whose effects are specific to vertebrates – even though widow spiders primarily prey on
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invertebrates (Garb & Hayashi, 2013). α-latrotoxin originated in a common ancestor of the

Latrodectus and Staetoda genus (e.g. faDlse black widows) but evolved a far greater vertebrate-
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specific toxicity in Latrodectus soon after their divergence (Garb & Hayashi, 2013). In humans,
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α-latrotoxin produces severe muscle pain, cramps, nausea and other complications that can be
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incapacitating for days and remain debilitating for weeks thereafter (Maretić, 1983). Since the
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advent of antivenom, mortality rates are less than 1%, but reports for pre-antivenom
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populations range Afrom 4% to 8% for healthy adults (Bettini, 1964). Widow spider bites pose an
even more significant physical threat to pregnant (Russell, Marcus, & Streng, 1979; M. D. Wolfe,
Myers, Caravati, Rayburn, & Seifert, 2011), young, elderly, and infirm individuals (Müller, 1992).
In the consideration of just one spider genus, it appears that a number of Latrodectus
species with potent, vertebrate-specific venoms populated Africa long before hominoids and
cercopithecoids diverged (Steiper, Young, & Sukarna, 2004) and have coexisted there with
hominoids for tens of millions of years since. This increasing paleobiological evidence
corroborates the common presumption that humans were at perennial, unpredictable, and
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significant risk of encountering highly venomous spiders in their ancestral environments. Even
when not fatal, a widow spider bite in the ancestral world would often still leave one
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incapacitated for days or even weeks – terribly exposed to other dangers and/or a considerable
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burden to family and friends.
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But avoiding spiders and such serious consequences is not difficult, providing they are
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noticed in time. Widow spiders, though, are typically darSkly-colored (black or brown) with body
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lengths as small as 8 mm and typically hide in dark recesses. Detection, therefore, is the critical
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arbiter of success in such encounters – any improvements to the sensitivity, vigilance,
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reliability, and speed of faculties for their detection would have been of significant selective

advantage. Proponents of the Snake DeDtector theory have similarly reasoned that predation
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from snakes primarily drove catarrhine species towards more sophisticated detection abilities
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rather than physical defenses such as a physiological resistance to venoms (Isbell, 2006; Le et
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al., 2013). The perceptual mechanisms for avoiding venomous bites appear to be more cost-
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effective than the physiological measures necessary to survive them asymptomatically.
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Since spideArs were of far greater significance to survival in ancestral environments than
they are in today’s environment, they constitute a uniquely well-suited test category of
inherent – that is, not acquired – attentional priorities (New et al., 2007). Any ability of these
ancestral threats to capture attention and awareness may persevere today – despite their
infrequency and inconsequentiality to modern life – as adapted behavioral vestiges of our visual
cognitive systems: not as attentional priorities acquired haphazardly through experience (Coss
& Goldthwaite, 1995).
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Spiders and snakes have been examined with most of the paradigms used to measure
attentional capture – though often with mixed results. In the most-used paradigm, visual
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search, spiders and snakes have been inferred to capture visual attention via their efficient
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detection in visual search tasks (LoBue & DeLoache, 2008; Öhman, Flykt, & Esteves, 2001a;
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Pflugshaupt et al., 2005). However, other visual search studies have suggested that such ready
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detection might be common to all animals – both threateSning and nonthreatening (Jackson &
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Calvillo, 2013; Lipp, Derakshan, Waters, & Logies, 2004; Tipples, Young, Quinlan, Broks, & Ellis,
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2002) or to all threatening objects – both ancestral and modern (Blanchette, 2006; Brosch &
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Sharma, 2005).

There are many factors involvedD in the visual search task that can complicate the
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inference of attentional capture. Visual searches are conducted with top-down guidance (J. M.
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Wolfe, Horowitz, Kenner, Hyle, & Vasan, 2004) and search templates (Schmidt & Zelinsky,
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2009), that can differ in effectiveness between categories of real-world objects (Levin, Takarae,
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Miner, & Keil, 2001). Further, training can imbue entirely neutral targets with attention-
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recruiting propertiAes (Kyllingsbæk, Schneider, & Bundesen, 2001; Shiffrin & Schneider, 1977),
and the visual search task itself commonly broadens the distribution of attention which can
generally increase detection efficiency (Belopolsky, Zwaan, Theeuwes, & Kramer, 2007).
Therefore, the efficient detection of any such categories of objects (e.g. snakes, butterflies, and
needles) in conventional visual search tasks may not clearly adjudicate between objects that
automatically capture attention and awareness, and those whose detection is mediated by a
combination of implicit and explicit factors (Cave & Batty, 2006; Most et al., 2005).
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In a related paradigm, the irrelevant singleton task, the addition of spiders to an array
interfered with viewers’ searches for a target object – despite the spiders’ irrelevance to the
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prescribed task. However, butterflies did so as well, and the apparent diversion of attention
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from the prescribed task to both animals was especially pronounced in individuals highly fearful
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of spiders (Devue, Belopolsky, & Theeuwes, 2011). The expectation that spiders would be
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displayed increased the spider-fearful participants’ monitSoring for – and interference by – both
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fear-relevant and neutral stimuli. Yet, even those especially fearful individuals were capable of
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ignoring the appearance of additional objects when spiders were very unlikely to appear. Such
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probability information – deducible from repeated presentations of salient stimuli – can guide

attention and monitoring whenever (DeDvue et al., 2011) and wherever warranted (Notebaert,
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Crombez, Van Damme, De Houwer, & Theeuwes, 2010).
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The evidence for ancestral threats being prepared – or inherently prioritized – for
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attention is thus generally mixed but also commonly complicated by top-down information and
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guidance. Undoubtedly, the ability to quickly find threats of all kinds when trying or alerted to
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do so is of great suArvival value. However, dangers such as spiders and snakes occur
unpredictably and generally so infrequently that they need to be detected and brought to
awareness largely absent any foreknowledge, intentions, or expectations. To minimize such
top-down control, the current study presented spiders – a prototypical ancestral threat – using
the inattentional blindness (IB) paradigm. Here, an unexpected stimulus is presented
peripherally to—and coincidentally with—a central, task-related stimulus (Newby & Rock,
1998). The experimental stimulus is only tested in one trial for each participant, since even one
presentation of a stimulus can facilitate the detection of subsequent occurrences via priming
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(Tulving & Schacter, 1990) and/or expectations (Mack & Rock, 1998). The IB paradigm is thus a
very rigorous measure of attentional capture relative to approaches that repeatedly display
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experimental stimuli. Importantly, the IB task more closely emulates the conditions under
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which humans have typically encountered spiders and snakes in their ancestral and modern
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environments, that is, largely without foreknowledge, warning, or task-relevance.
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The IB paradigm can not only measure how likely Sunexpected objects are to be
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detected, but which of their qualities (e.g. location, shape) are registered during their single,
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brief exposure. The real-world function of attentional capture is to recognize significant objects
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and events and prompt some adaptive response. The ability to divert attention from current

tasks is a necessary but not sufficient quDality of threatening objects and events, whether
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ancestral or modern. As Most and colleagues reason, should a child appear in front of your car
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as you tune the radio, the important result is not that you are slower turning the radio knob, it
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is that you steer away from the child (2005). The threshold of success for perceiving threats is
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particularly high: that is to become aware of their presence, their location, and critically for
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reacting adaptivelyA – their identity. Being distracted from a possibly crucial task while
remaining unaware of the potential threat constitutes the worst of both worlds.
In light of their evolutionarily-persistent threat to survival, spiders are hypothesized to
be exceptionally capable of capturing attention and propagation into conscious awareness even
when completely unexpected and irrelevant to any exigent goals. We predicted that iconic,
prototypical spiders (Figure 1.A and 1.C) will be very frequently detected, located, and
identified when presented in an inattentional blindness task. This was tested in a first