Finding and hiding things

Why are visual search and camouflage linked?

Camouflage can be seen as disrupting visual search

What broad theme do camouflage strategies demonstrate?

Effects of evolutionary pressure on visual processing

What is visual search?

Searching a display to find a target, often the “odd one out”

Why is visual search called an umbrella term?

Like attention, it covers many different processes and tasks

What is a common visual search experiment?

Finding whether a target is present among distractors

What does search slope measure?

How much reaction time increases per additional item

What does a steep search slope suggest?

Difficult or inefficient search

What does a shallow/flat search slope suggest?

Easy or efficient search

What does the intercept in visual search data represent?

Baseline processing time unrelated to number of items

Why is finding a white circle usually easier than finding an “L”?

Simple feature differences pop out more than subtle shape/configuration differences

What is camouflage broadly?

Any attempt to deceive perception

How can camouflage be understood in visual search terms?

As a visual search disrupter

What is background matching?

Matching colours/ patterns of the environment to blend in

What is crypsis?

Camouflage that prevents detection by making the target hard to see

What does background matching mainly prevent?

Detection

What is the “back pocket” view of camouflage?

The simple idea that camouflage means looking like the background

Why is viewpoint important for background matching?

A pattern may match one background/ viewpoint but not another

Why does placement matter in background matching?

The animal must sit against a matching background

Why does viewing distance matter?

Patterns and colours can blend differently at different distances

Why does relative scale matter?

Pattern size must match the scale of the background texture

What is countershading?

Dark upper surfaces and lighter lower surfaces to reduce 3D shaping cues

What does countershading help nullify?

Effects of overhead lighting

What perceptual cue does countershading reduce?

3D shape-from-shading cues

Why might animal countershading be sub-optimal?

Other constraints such as abrasion, thermoregulation, and signalling

What is disruptive camouflage?

Camouflage that breaks up the recognisable shape of a target

What does disruptive camouflage mainly prevent?

Identification

What is external disruption?

Breaking up the edges that define the target’s characteristic shape

What is internal disruption?

Distracting from the true edges of the target

What is surface disruption?

Interfering with 3D cues to surface shape

What is differential blending?

Some pattern parts match the background while others stand out

What is maximum disruptive contrast?

Conspicuous pattern elements that strongly break up shape

Does disruptive camouflage require exact background matching?

No

Why might disruptive camouflage work in more places than pure crypsis?

Even partial colour matching plus shape disruption can be effective

Why can disruptive camouflage “get away with less”?

It does not need perfect background matching

What is mimicry of mimicry?

A hoverfly resembling a wasp

Why does a hoverfly benefit from resembling a wasp?

Predators may avoid it because wasps sting

What is masquerade?

Appearing to be an irrelevant or meaningless background object

How is masquerade different from mimicry?

Mimicry resembles a meaningful object; masquerade resembles something unimportant

What does background matching prevent?

Detection

What does disruptive camouflage prevent?

Identification

What does mimicry/masquerade prevent?

Correct identification

Which strategy makes you “invisible”?

Background matching/ crypsis

Which strategy makes you unrecognisable?

Disruptive camouflage

Which strategy makes you look like something else?

Mimicry/ masquerade

What is aposematism?

Warning colouration advertising danger, toxicity, unpalatability, or defence

Is aposematism meant to hide the animal?

No, it is meant to be conspicious

What kind of signal is aposematism?

Honest signalling

What features are common in aposematism?

Bright colours and sometimes odours

How can aposematic colouration have dual use?

Warning at close range but background matching at long range

Why can bright colours become cryptic at distance?

They merge together visually into duller/ background-matching colours

Why is movement a problem for camouflage?

Motion makes detection much easier

Who argued colour schemes are little use if animals move

Theodore Roosevelt

Can animals hide while moving?

Sometimes, by matching environmental temporal dynamics

What is temporal background matching?

Matching movement patterns to the moving background

What example involves octopuses?

Octopuses walking on two tentacles while other arms mimic seaweed

What example involves stick insects?

Swaying in time with wind-blow vegetation

What example involves Jacky lizards?

Tail flicking changes with background motion

What are caustics?

Moving patterns of light in shallow water

Where else can dynamic light patterns occur?

Under tree canopies

What happens to light/ dark patterns when wind blows?

They move dramatically

What did human detection studies show about moving backgrounds?

Targets are harder to detect when their motion matches moving background statistics

What is dazzle camouflage?

A strategy that confuses perception of motion, shape, range, or boundaries

Why are ships difficult to camouflage traditionally?

They are salient and viewed against many backgorunds

Why did camouflage continue after radar?

Visual targeting still mattered in some conditions

What were early invisibility attempts for ships?

Painting them white or using countershading

What was dazzle claimed to disguise?

Range, heading, size, shape, and speed

What was dazzle’s specific military aim?

To counter U-boat torpedo attacks

Why were torpedo attacks perceptually difficult?

Brief periscope views, poor conditions, and need to predict future ship position

Why is predicting heading important for torpedo attacks?

Torpedoes are slow and must intercept the target’s future path

How might dazzle affect range estimation?

By making binocular image fusion harder

What is the correspondence problem?

Determining which parts of two images match

How might dazzle affect heading?

By disrupting texture-gradient cues

What visual illusion relates to perceived size in dazzle?

Helmholtz squares

What do Helmholtz squares demonstrate?

Patterns can make identical shapes appear taller/thinner or shorter/fatter

How can dazzle affect shape perception?

Through surface disruption

How much complex 2D dazzle reduce perceived speed?

Around 7%

How large can speed distortions be with moving dazzle texture?

Up to about ±15%

Which animal is often linked to dazzle camouflage?

Zebras

What is one claim about zebra stripes?

They may reduce fly landings

What is the confusion effect?

Reduced predator attack success because individuals in a group are hard to single out

What casuses the confusion effect?

Predator confusion and cognitive bottlenecks

Why does the confusion effect resemble visual search?

Predators must locate/ track a target among many distractors

How does the confusion effect differ from typical visual search tasks?

Items move and the task is tracking, not just target present/ absent

What factors may influence the confusion effect?

Unpredictability, density, colouration, and motion

Why can gradual movement changes be protective?

Humans find slow changes difficult to notice

What animal example illustrates gradual change?

Cats stalking prey slowly