signalling 4- signal design Flashcards
What is the main idea of this lecture on animal signals?
Signals are designed to contain and convey accurate information (signal content) and to ensure that information is effectively transmitted and received (signal efficacy).
what is signal split into
- production cost
- efficacy cost
- consequence or social cost (covered in prev lecture
What does ‘signal content’ refer to?
It refers to the inherent information in the signal
How does ‘signal content’ influence signal form?
The form of a signal must be related to the information it carries; for example, gerenuks use their eyes to convey vigilance.
What is ‘efficacy cost’ in signal design?
It is the additional design feature or effort that ensures the signal is clearly transmitted,
such as conspicuous and obvious facial markings in gerenuks to make vigilance more visible and effectively transferred.
Why are signals often elaborate or extravagant?
Because ensuring signal efficacy (clear transmission) often involves mechanisms like redundancy, amplification, and exploiting receiver psychology, leading to complex designs.
What is the central challenge in understanding animal signal design?
Explaining why signals appear so exquisite and complex, and investigating how receiver psychology and evolutionary pressures shape these signals.
What is an icon in the context of animal signals?
An icon is a signal where the form itself directly represents its meaning (e.g., the honeybee waggle dance indicating direction and distance to food).
What are amplifiers in animal signals?
They are features that enhance the visibility or efficacy of a signal without changing the underlying information conveyed, such as bright coloration that makes a display more noticeable.
Can you give an example of amplifiers in fish?
In blue haired wrasse, vibrant blue and green colors amplify aggressive displays in clear Caribbean waters, and a black dot on the fin amplifies courtship signals by making fin movement more visible.
How do Bar-tailed Godwits illustrate amplifiers?
Their feathers have thick white borders contrasting with brown bases, making any imperfections (diet and fights) more visible and thus amplifying information about individual condition.
Integration of Icons and Amplifiers
Gerenuks use direct stare (iconic signal of vigilance) plus facial markings (amplifiers) to enhance visibility of their gaze and alertness to predators - conveying informational effectively
Why is receiver psychology so important in signal design?
Because the way receivers perceive and process signals shapes the evolution of those signals, driving them to become more effective and elaborate.
What evolutionary mechanism maintains icons and amplifiers?
- Natural selection preserves if these signals and efficacy increase the sender’s fitness enough (e.g., better predator deterrence or more successful mating), even though the exact evolutionary history can be hard to trace.
Summary of Critical Concepts
- Receiver Psychology shapes signal design
- Icons convey meaning directly (honeybee dance)
- Amplifiers enhance signal visibility (wrasse colors, bird feather edges)
- Signals can integrate both (gerenuk vigilance display)
How do icons and amplifiers fit into a broader framework of signal design?
They are part of two main design functions: content (carrying information) and efficacy (enhancing clarity and transmission).
What are the two overarching design functions introduced in this section?
1) Content: conveying information (e.g., icons like the honeybee waggle dance), and
2) Efficacy: ensuring signals are transmitted and perceived effectively (e.g., amplifiers).
What example illustrates the ‘content’ aspect in signals?
The direct staring behavior of a gerenuk or the honeybee waggle dance, where the form itself carries the core information.
What three ways can efficacy enhance an animal signal?
1) Improve color transmission (blue-headed wrasse),
2) Stimulate more of the receiver’s sensory system (anolis lizard’s dewlap),
3) Amplify signal readability (body stripe in spiders).
How do anolis lizards use a dual signal to defend territory?
They combine head bobbing (content) with dewlap extension (efficacy), ensuring the message is both informative and highly visible.
What did neural motion models (2010 study) reveal about anolis lizard displays?
They showed that head bobbing and dewlap extension are designed to trigger specific visual responses in receivers, highlighting the importance of efficacy.
Neural motion models (from a 2010 study) confirmed that these signal components are designed to trigger specific visual responses in receivers.
What is the Handicap Principle according to Zahavi?
It suggests signals are reliable because they are costly to produce, ensuring only high-quality individuals can afford them.
* production, efficacy and consequence/social costs
* more correlated the cost and the signal, more reliable it becomes
What is the ‘in principle’ problem in signal costs?
It highlights that all signals incur some cost (low or high), and these costs are paid because effective transmission requires design features that increase efficacy.
Production Costs vs. Efficacy Costs
- Production Costs (Handicap): Direct expenses in creating elaborate signals (e.g., peacock’s train).
- Efficacy Costs: Investments into signal design ensuring the signal is noticed (e.g., large, brightly colored signs).
Why is understanding receiver psychology important for distinguishing costs?
Because it reveals whether the main expense is in creating the signal itself (production) or making it more visible/effective (efficacy).
How do peacocks illustrate both production and efficacy costs?
Their large, vibrant eye spots require significant resources to grow (production cost) and also make the display more attention-grabbing for females (efficacy cost).
What did Petrie et al. (1991) discover about peacock trains?
Larger, brighter eye spots correlate with better offspring growth and survival, indicating condition-dependent signaling.
Why is a mechanistic approach crucial in studying signal design?
It helps determine exactly how signals are produced and perceived, clarifying the relative roles of production vs. efficacy costs.
Summary of Critical Concepts (Part 2)
- Content vs. Efficacy: Both matter for successful communication.
- Anolis Lizard Displays: Separate content (head bob) from efficacy (dewlap).
- Costs & Reliability: Production vs. Efficacy costs influence signal honesty.
- Mechanistic Analysis: Key to distinguishing different costs in signal design.
Condition Dependent Indicators
These are signals whose form reflects the underlying physiological and genetic quality of the signaller (e.g., a peacock’s bright feathers).
How do peacock feathers serve as multi-modal displays of efficacy cost?
They show condition-dependent color and eye spots that require resources to produce (production cost) and create a large, visually striking display that captures attention (efficacy cost).
Why is redundancy (multiple eye spots) important in peacock displays?
Repetition enhances message recall; even a brief glance ensures the receiver sees enough eye spots to fully process the signal.
* even one eye spot can ensure the receiver understands the underlying information
What are three possible efficacy effects of the peacock’s train?
1) The large display dominates the receiver’s visual field,
2) Multiple eye spots provide repeated visual measurements,
3) Eye-like patterns trigger innate attention mechanisms in receivers = subliminal association alerts attention
How can ‘tricking’ a receiver still be mutually beneficial?
If the peacock’s display elicits a mating response and leads to successful reproduction, both signaller and receiver benefit, maintaining the signal’s evolutionary stability.
3 ways of multi-component displays which exploit receiver bias
- Condition Dependent Indicators
- Amplifiers
- Other features that exploit receiver psychology
- allows multiple messages conveyes, and exploits pre-existing receiver bias
Additional Exploitation of Receiver Psychology
- Mantis Shrimp: Claw spots may mimic predator cues or draw focus subliminally.
- Egg Mimic Darter: False eggs on the dorsal fin guide females to spawning areas.
- Cichlid Egg Mimics: Male anal-fin spots resemble eggs, ensuring females in correct positioning for fertilization.
Why do these ‘mimic’ strategies work?
They exploit pre-existing sensory or cognitive biases in receivers, drawing attention to the critical area or signal component needed for reproduction.
What is the final integration of signal content and efficacy?
Signals must carry accurate information (content) and be effectively transmitted (efficacy) through mechanisms like redundancy, amplification, or exploiting sensory biases.
How do production costs differ from efficacy costs in signal design?
Production costs are tied to creating the signal itself (e.g., growing feathers), while efficacy costs ensure the signal is clearly perceived (e.g., bright colors, large size, more extravagent part of signal design).
What role does receiver psychology play in evolutionary stability?
Receivers’ sensory biases and cognitive processes shape which signals persist; signals that exploit these biases effectively are maintained as long as they provide mutual benefits.
How can cheating be limited in these signaling systems?
If deception becomes too frequent or detrimental, natural selection favors receivers that detect it. Mutual benefit and reliable signals thus remain favored.
Summary of Critical Concepts (Part 3)
- Condition Dependent Indicators: Reveal genetic/physiological quality.
- Exploiting Receiver Psychology: Eye-like patterns, mimic strategies.
- Multi-Component Displays: Combine icons, amplifiers, and redundancy.
- Content vs. Efficacy: Balancing accurate info with effective transmission.
- Reliability & Mutual Benefit: Key to stable evolutionary signaling.
