Signals & Cues from Appearance Flashcards
Why do we look for cues from appearance?
Predict & prepare for behaviour of others
- current motivation
- attentional focus
- current actions & preparation
- current health
Dawkins
- used for ‘mind reading’ and manipulation
- wolf bares teeth before attack
- observer recognises signal
- valid signals (always/often followed by behaviour) allow for manipulation
- bare teeth with no intention of attacking = deceptive signal
What are signals?
- Traits that change another organism’s behaviour
- Benefit sender & have evolved for this function
- Effective through the evolved response of the receiver (Stegmann, 2005)
- Receiver gets some kind of benefit (e.g. not being eaten), but not necessarily a desirable payoff
- Must be useful enough for observer to attend
- Creates pressure for deceptive signals - others can be used as tools (Krebs & Dawkins, 1984)
Signal system of the spangled drongo
Flower et al., 2012
- warns meerkats of predators but give occasional deceptive calls, eats their food as they hide
What keeps a signal honest?
Costs
- associated cost depends on conflicting interest between sender and receiver
- evolutionary arms raec
Signals in mate choice
Conflict of interests
- males exaggerate fitness
- females must detect this exaggeration
- if the signal is not costly the system collapses - signal must show off fitness!
Signals in parental investment
Conflict of interests
- chicks exaggerate need for self benefit - manipulation of parents
- cost on siblings and parents’ fitness
Brood parasites
- parents respond to hunger signal - chick’s open mouth
- cuckoo bird - lay eggs in nests of other birds - cuckoo chick kills other chicks (pushes eggs out) has stronger signal - brighter red colouration inside mouth
- enormous cost to parent - cuckoo chick’s dietary requirements outway parent’s
Honest signals between species
Gazelle stotting
- predators (big cats) target weaker prey
- stronger gazelles stot (jumping) when they spot a predator
- honest - takes a lot of effort
- benefits individual gazelle to perform (not eaten) and predator to attend (better chance of catching prey)
Direct and indirect signal costs
Direct
- cost during signal production (e.g. takes effort, leaves self vulnerable)
Indirect
- via consequences of production / false signals (e.g. chance of conflict)
Human facial expressions
Readily signal emotional states to others
Sikka et al., 2015
- Children good at manipulating parents with false signals of pain
- brow lowered, lid tightened, eyes closed
Smiling
Mehu et al., 2007
- positive expressions facilitate trustworthiness and signal co-operation
- Altruists smile more when sharing
Smiles can be faked! - occasional false smile might win co-operation w/o genuine positive interest from sender (it’s in the eyes)
Centorrino et lal., 2015
- Frequency of real smiles predict genuine affiliative behaviours
Scharlemann et al., 2001
- Social rejection increased ability to discriminate between smiles
Static signals from the human face
Masculinity
‘Immunocompetence’ theory
- Pound et al., 2009
- T influences male face shape (jaw, brow)
- Roberts et al., 2004
- T is an immune system stressor
- Zahavi, 1975
- Only highly immunocompetent males (strong immune system) can ‘afford’ to ‘spend’ T on masculine facial shape
Honest signal!
BUT - children of masculine-looking men aren’t regularly healthier
Women look more at skin colouration for health signals
Scott et al., 2012
- Lack of consistent cross-cultural support
- animal literature on sexual ornaments and immunity doesn’t support
- facial masculinity doesn’t really contribute to attractiveness
- Masculinity as an intrasexual signal of dominance
Physiognomy
The idea that a person’s personality can be read from their facial appearance - comparing to nature of animals people look like
Signals of personality from the face
Kramer & Ward, 2010
- agreeableness, extraversion, neuroticism, physical health signalled from human face
- averages of e.g. extraverted vs introverted people are distinguishable
- internal features (eyes, nose, mouth) enhance an interfere with detection of signals
Facial appearance and sociosexuality
Boothroyd et al., 2008
- Women can identify men interested in ST relationships, sex w/o love etc. from their faces
- Men couldn’t, but found the women that were more attractive
Signals from the human face
Where in the face?
Burt & Perrett, 1997
- age, attractiveness, gender from right side of face
- emotion from left
Jones et al., 2012
- Right and front of face have same accuracy in predicting personality
Kramer & Ward, 2010
- Composite images - women scoring high/low on personality & health dimensions
- Big Five traits & physial health accurately discriminated from just internal facial features (bar conscientiousness)
- Internal + external features –> improved detection for extraversion & phys health, poorer for openness
