signal coding definitions types of coding schemes inferring sender and receiver coding signal...
Post on 19-Dec-2015
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Signal coding
• Definitions
• Types of coding schemes
• Inferring sender and receiver coding
• Signal function and coding
Conflict resolution example
Signal definitions
Assumptions
• Senders produce signals in order to provide honest (accurate) information to receivers– Dishonest signalling will be considered in the
third section of the course
• Communication involves signal production, transmission, and reception. All three processes influence the accuracy of any coding scheme
Coding matrix
Probability of giving a signal in each condition. Sender matrixmust be similar to Receiver matrix for communication to occur.
Coding conventions
• None - all probabilities equal
• Perfect - each signal coocurs with each condition
• Imperfect– Specific - one signal per condition, but
conditions may not be discriminable– Unique - one or more signals per condition
Reasons for imperfect coding
• Sender– Errs in assessment of condition– Mistakenly assigns signals to conditions
• Receiver– Signal is modified by transmission– Errs in identifying signal– Has not yet learned correct signal
Coding schemes
• Codes require signal diversity
• Variation can be created by – Modifying signal element attributes
• Sound: amplitude, frequency, duration
• Light: color, size, location
– Combining signal elements in series
• Signal elements must be perceptually distinct
Hierarchical syntax
Stereotypy
Stereotypic signals may represent constraints on senders
Coding options
Coding scheme examples
Iconic aggressive signals
Inferring sender coding schemes
• For discrete conditions and discrete signals, use contingency table analysis
• For discrete conditions and continuous signals, use discriminant function analysis
• For continuous signals and uncertain conditions, use clustering or principle component analysis
Phyllostomus hastatus
Females form stable groups
Departing bats give screech calls
Bouts of screech calling often coincide with group departures
Calling rate and diet varies with season
Calling females recruit group mates
Groups have distinct calls
Inferring receiver coding schemes
• Determine how receiver categorizes the set of signal variants– In captivity, present alternative forms to
determine which are perceived as same or different using habituation-dishabituation expt or operant conditioning paradigm
• Determine which condition is associated with each category by the receiver
Females can discriminate group mates by call
Compound coding schemes
• Combination mapping– Combining information into a single signal can save
energy and reduce exposure
• Parameter mapping– Body size covaries with pitch, energy reserves
covaries with calling rate
• Hierarchical mapping– Mean differences denote group, individual
differences denote individual
Tamarin group calls
Signal ontogeny
• Heritable• Favored when coding scheme is predictable, e.g.
individual or kinship differences
• Learned– Individual or trial-and-error– Social
• Critical period vs. open-ended
• Believed to be faster and avoids costly errors
Females learn to match calls
Group 1 Group 2
Before
5 monthsafter move
Signal function and coding
• Binary assignment– E.g. sex labels– need only 2 signals, can be heritable
• Binary recognition– need many signals– decide own vs other
Signal function and coding
• Binary comparison - often continuous signals– opponent fighting ability, threshold mate
choice, best-of-n mate choice
• Manifold decisions– Iconic rule - Honeybee language– pairwise associations