- A stereotyped pattern of moment of a part of the body that is reliably elicited by presentation of specific stimulus 

- All reflexes involve an innate relationship b/w stimulus and a response

-Feedback system

- Stimulus intensity below which no response is elicited and about which a response always occur

- Threshold is stimulus intensity that elicits a response 50% of the time

the (involuntary) movement or change in orientation of entire animal.

First studied by Loeb (1900)

- Called tropisms forced movements

- Implying no involvement of intelligence, will, or choice.

Types of tropisms

Kineses (random movement) & Taxes (directed movement

A tropism in which the direction of the movement is random in relation to the stimulus 

Wood Louse: humidity-seeking bx

A tropism in which the eliciting stimulus determines the direction of the organism’s movement.

Photo-taxes of maggots (movement away from any bright light)

An innate pattern of Bx that is elicited by a specific stimulus and, once started, continues to its end whether the stimulus is present or not.

- A part of the repertoire of all members of a species

- Performance of the Bx is not a result of prior learning

- The Bx is initiated by a specific stimulus (sign stimulus)

- The Bx occurs in a rigid order

- Once initiated, it continues to completion

An innate sequence of Bx in which the progression from one Bx to the next depends on the presence of specific stimuli.

Portions of the sequence may be skipped or omitted. 

Reaction chains differ from FAPs.

If stimulus is not present, sequenced behavior will not occur.

Reese (1963): Hermit Crab