Stereotypy, flexibility and coordination: key concepts in behavioral functional morphology

Abstract

SummaryAnimal movement and its muscular control are central topics in functional morphology. As experimentalists we often manipulate stimuli in a controlled setting or compare species to observe the degree of variation in movement and motor control of particular behaviors. Understanding and communicating the biological significance of these sources of variability requires a universal terminology that is presently lacking in the functional morphology literature. We suggest that ʻstereotypyʼ be used to refer to the degree of variability observed in a behavior across trials under a given set of conditions. The ability of an organism to alter its behavior across experimental treatments is referred to as ʻflexibilityʼ. We discuss how there has been a tendency to confound the phenomenon of a behavior exhibiting low variability, which we refer to as stereotyped, with inflexibility, or the inability to alter the behavior in response to a change in stimulus. The degree of stereotypy and flexibility in a behavior need not be correlated, nor need they have a common underlying basis. Coordination, a term used to describe the relationship between different body parts during movement, can be stereotyped and can show flexibility. Stereotypy of coordination can be assessed by the strength of correlations between movements of two body parts. The influence of coordination coherence on behavioral performance has rarely been considered, and could shed light on how taxa differ in their ability to perform behaviors. We suggest definitions of the terms stereotypy, flexibility and coordination, and provide examples of how and when these terms could be used when discussing behavioral changes in functional morphology.

Comparative feeding kinematics and performance of odontocetes: belugas, Pacific white-sided dolphins and long-finned pilot whales

“…Several analyses support the conservation and coordination of a posteriorly directed 'wave of buccal expansion' among odontocetes (Summers et al, 1998;Wainwright et al, 2008). The sequence and timing of kinematics appear conserved among odontocetes (Fig.4), with a posteriorly directed wave of expansion from the tips of the jaws through the hyolingual apparatus.…”

Rhythmic chewing with oral jaws in teleost fishes: a comparison with amniotes

“…To compare levels of variation, it is necessary to use measures that account for the strong correlation between mean duration of the behavior and the standard deviation for the behavior stemming from the fact that cycle duration variance increases with cycle time (Ross et al, 2007a;Wainwright et al, 2008). This was done in two ways.…”

“…In support of this hypothesis, Ross and colleagues showed that mammalian chew cycle durations not only are less variable than those of lepidosaurs but also increase with mandible length, which does not occur among lepidosaurs. These authors hypothesized that improved chewing rhythmicity, a form of stereotypy (sensu Wainwright et al, 2008), enables mammals to chew for longer, facilitating the acquisition of the greater amounts of food required by their elevated metabolism (Nagy, 2005). Ross and colleagues also suggested that size-related changes in chew cycle durations in mammals support the hypothesis that energy consumption during chewing is minimized by adjusting chew frequency to the natural frequency of the chewing system (Ross et al, 2007a).…”

Structured variability of steady-speed locomotion in rats

“…However, gait mechanics are not perfectly reproduced between steps, leading to some level of variation even under restricted conditions (Wainwright et al, 2008). In particular, small quadrupedal mammals would be expected to match their high level of structural flexibility [flexed three-segmented limbs with low limb stiffness when running (Farley et al, 1993;Fischer et al, 2002)] with high functional variation during locomotion.…”