Finding and hiding things Flashcards
Evolutionary balance
between camouflage and looking nice
What is visual search
umbrella term involving displays where have to find the odd one out.
can vary in difficulty
Typical data of visual search
cost of adding items to display
for efficient search - low attention requirements RT stays consistent
for inefficient search higher attentional requirements RT increases. steeper for checking if target if absent
What is camouflage
visual search disrupter
often in conflict with other constraints such as impressing potential mate
avoid trouble outside ring (1)
Don’t be there and avoid predators
Avoid trouble ring 2
don’t be detected
hide
background matching
Background matching
coloured and patterned like background
prevents detection
view point important (sharks)
Things impacting background matching
Placement matters- same texture but off placement means no camouflage
viewing distance- further away off-set predator so more camouflage
Relative scale matters- how far from the background is the target
Background matching and counter shading
light on bottom dark on top
try to limit cues from shadows so appear smaller when light hits from top.
photograph paper baby dear- patterning is suboptimal other constraints such as abrasion (lots of colour), thermoregulation and signalling
Avoid trouble 3
Don’t be recognised
disruptive camouflage
mimicry/masquerade
disruptive camoflauge
external - break up edges that define shape of target
Internal- distract from edges
Surface disruption - interfere with 3d cues to surface shape
Differential blending - some parts of pattern matched to background while others stand out
Maximum disruptive contrast- parts that stand out should be conspicuous (clearly visible)
prevents detection
Disruptive camouflage examples
visual search task - find odd shape. all shapes have shapes inside which disrupt edges
frogs
planes
Mimicry/Masquerade
mimicry- pretend to be something unpleasant
Masquerade- look like something not of interest
prevents correct identification
Background vs disruptive
background - only works in one place
Disruptive- works in more then one place
both equally effective
Avoid trouble 4
Don’t be chosen
Aposematism
Aposematism
bright yellow or high contrast colours
secondary defences
Dual use
wasps - Aposematic at close range and background matching at long range
What breaks most camouflage
motion
Avoid trouble 5
Don’t be caught
Background matching
Dazzle
confusion effect
move slowly
Background matching movement examples
match temporal dynamics to those in environment (both temporospatial domains)
octopus walking
stick insects swaying
Jacky lizards tail flicking - change rate of tail flicking to match background
Evidence for dynamic background matching
study
generate land and water and add shadows and light. add targets and move them. if move on moving background harder to spot
Dazzle
camouflaging ships -stripy ships
aim is confusion not concealment
difficult viewing conditions
Dazzle work?
Range- triangulation relied on fusing two images - harder as which stripe belongs with which stripe
Heading (direction)- texture gradient acts as monocular depth cue
size- Helmholtz squares orientation impacts size.
shape- harder to decipher shape as acts as surface disruption
speed - 7% decreased perceived speed. moving texture dazzle impacts 15% speed distortion
Dazzle in nature
zebra
horse flies don’t like patterns on horse - struggle to land
cuttle fish - move patterns across surface shift perceived location while hunting
