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