Lecture 2.docx

Lecture 2: Tinbergen’s 4 Whys Ontogeny (Development) How does the behavior emerge over the lifetime of the individual? Mechanism (Immediate Causation) What are the neural, physiological and psychological processes that produce and regulate the behavior? Phylogeny (Evolutionary History) When and how...

Lecture 2: Tinbergen’s 4 Whys Ontogeny (Development) How does the behavior emerge over the lifetime of the individual? Mechanism (Immediate Causation) What are the neural, physiological and psychological processes that produce and regulate the behavior? Phylogeny (Evolutionary History) When and how did the behavior emerge in the evolution of the lineage to which the species belong? Function (Adaptation) How does (if it does) the behavior contribute to the survival and reproduction One of the Founders of the Modern Theory of Evolution in the 1940s Ernst Mayr (1904-2005) Speciation in Birds Harvard professor of organismal biology dealing with the rise of molecular biology Proximate Causes The processes that produce biological features (cause) Ultimate Causes The consequences of biological features that increase the survival and reproduction of organisms (function) Why Is this bird singing? Proximate Factors: Causation (physiological explanation) Sensory/nervous system Hormonal systems Skeleto-muscular system Development/Ontogeny Learning, genetic disposition, developmental mechanisms Ultimate Factors: Adaptive Advantage/Function Reproductive success What are the selective pressures Evolutionary History/Phylogeny How song evolved in the bird’s ancestors Development as Function Ontogenetic adaptations Problem: Getting out of an Egg Solution: The egg tooth A feature common to vertebrates that hatch out of eggs Development is a dual problem: achieving the adult form (maturing mechanisms) and surviving at all stages (age-specific functions) Not All Features Have a Function Not all traits can be readily attributed to a function solving a specific problem Fetal vs Adult skull – What is the adaptive function of humans and other mammals having unfused skull sutures at birth? To get out of a tight birth canal Problem – Non-placental mammals whose infants do not face the difficulty of squeezing the head through a tight birth canal also have unfused skull bones at birth. Problem 1: Marsupial mammas give birth to tiny embryos Problem 2: Monotreme mammals lay eggs Birds, reptiles and other vertebrates in which the young hatch out of an egg also have unfused skull bones at hatching The Wrong Solution for the Wrong Problem: Squeezing through a tight birth canal cannot explain the common pattern of unfused skull bones at a comparable age in all vertebrates A more likely explanation is that the unfused skull bones is a by-product of how the skull develops This is an example of how mechanisms unfolding over development may not need a functional explanation The Forgotten Lessons Integration Description Precedes Explanation What is the Behavior that we are trying to explain? Play Fighting in Rats It resembles serious fighting Proximate Explanation: It is an immature form of adult fighting Ultimate Explanation: It provides practice for adult fighting skills Serious Fighting in Rats There are similarities but, More head, mid-body, lower body attacks; less nape of the neck Play Fighting Versus Serious Fighting in Rats Compete to gain access to different body targets In play the nape is nuzzled with the snout if contacted, but in fighting, the lower body is bitten These differences in targeting leads to modifications in the tactics used Revised Description Leads to Revised Explanations Play fighting only superficially resembles serious fighting Proximate Explanation: Play fighting is NOT immature serious fighting Ultimate Explanation: Play fighting does NOT provide practice for adult fighting skills The Forgotten Lessons Integration Description Precedes Explanation What is the Behavior that we are trying to explain? How can we measure it? Jaak Panksepp – The Godfather of the study of the neuroscience of play Choosing Measurable Units Easy to identify and score High intra- and inter-observer reliability (a) Dorsal contact, (b) Pin Big Brains are More Motivated to Play Decortication should reduce the amount of play Nape contacts show that decorticates are just as playful as intact rats, but pins show that decorticates are less playful The Organization of Play Fighting in Rats Attack and defend the nape of the neck, which if contacted is nuzzled with the snout To defend the nape a set of rat-typical defense tactics are used to prevent the partner from contacting the nape Accounting for the Change in Number of Pins Could be due to reduced number of attacks or a decrease in the likelihood of defending against a nape attack (neither differ from that of intact rats) The decorticate rats are less likely to use defensive tactics that lead them to ending in the pin configuration (decorticate rats are more likely to use standing defensive tactics) The Role of the Cortex In the absence of the cortex, rats are not less motivated to engage in play But they do prefer to use tactics that lead to different patterns of playful wrestling Without knowing how pins are achieved, scoring pins can be misleading Deriving Measurable Units Dynamic analyses help identify units of behavior that reflect the underlying organization of that behavior To be useful, these units should yield measures that have high intra- and inter observer reliability