AN OUTLINE OF OBSERVATIONAL METHODS AND TECHNIQUES

Transcription

1 AN OUTLINE OF OBSERVATIONAL METHODS AND TECHNIQUES [These notes are written in a succinct, compressed style. You may wish to add on your own notes when we go over these topics in the workshop] How to begin. Adopt Preview Mode Just watch. Questions will occur. Give your brain time. You may never have this pristine view again! [this is the exact opposite of using a behaviour test in some big Neuropsychopharmacologicum] Do not hurry this very important preliminary phase Field notes Prior to the development of a well-honed set of descriptive categories (see below) in terms of which behaviour may be digitally coded some form of long-hand description of the behaviours one sees and is interested in will be made These can be in the form of written notes made, perhaps in shorthand, at the time (or during perusal of film material) Or as tape-recorded commentary Field sketches may also prove very useful Date and location of observations and other relevant information Care should be taken to document exactly where and when observations (or films on which they are based) were made Time into field and end of observation time should be recorded to provide total observation time Weather conditions and other main independent variables should be recorded Number and identity of organisms being observed should be noted: including any arrivals and departures of these during the observation period Measuring behaviour: categorisation Most observational records deploy a nominal scale of measurement The flux of behaviour is dissected into separable elements which are given names Often only the time of occurrence (for behavioural events), or the time of onset and offset (for behavioural states), is recorded Concatenations of such occurrences may be conceptualised as bouts Ordered occurrences of different elements may be conceptualised as sequences (there are analytical tools for the detection of sequences: see sequential analysis below) The occurrence of individual elements, or of groups of elements, in time may be found to have a repetitive structure or pattern (see section below on the analysis of temporal patterns) Some elements may be quantified in some way, such as the force exerted by a lever press, or the decibel loudness of a growl. This might involve a ratio scale of measurement. Notion of ethogram:

2 Full description of the entire behavioural repertoire of a species Should be made in environment of evolutionary adaptedness (EEA) Distortions in captivity, zoo and domestic animals: latter may have smaller brains: maybe EEE (early environmental enrichment) brings individuals closer to wild Individual as well as species features should be expected: recognition of individuals hugely enriches study of social life: ringing, natural markings, holistic jizz. Classically ethogram considered mainly a list of fixed action patterns (FAP) which were strongly genetically programmed ( hard-wired ) and perhaps were specifically motivated ( action specific energy ) and regulated by innate releasing mechanisms (IRM) Species-specific behaviour may not be entirely hard-wired: example of bird song: nestling genetically predisposed to learn song containing features of spsp song during a critical period. Must be practised to be performed and then crystallises into seemingly innate or instinctive pattern (in some species, not others). Value of experience for seeing particular behaviours in context of ethogram: when asked question about Bures 1-trial passive avoidance technique Konrad Lorenz s answer was I do not know the rat. Categorisation of behaviour If published ethograms exist, adopt them tentatively, but scrutinize them: don t accept them root, line, and branch. Different types of category: o description of movements: sometimes specific muscle contractions e.g. erections of various structures as part of display o definition by outcome: lever press, arm entry o specifying the location of the action, e.g. in measures of locomotory activity such as exploration o global versus specific o more high-level, interpretive categories: avoid: in the early days of comparative anatomy, each inexplicable organ was labelled excretory o lumping versus splitting: easier to split first, lump later: reverse impossible. o track records, such as (literally) footprints, or toothwear, or nests or other constructions, or sound spectrographs, or transcripts ( fossil behaviour) Social situations: when more than one individual is being observed we may also need to record: o Who is the actor o Who is the recipient (if the action is something done by the actor to another organism) Category label: evocative better than interpretive: wet dog shake cf. shudder with revulsion What is a good category? The following features are required

3 o Observer agreement in principle: experienced independent observers of the same behaviour of the same species or type of organism should endeavour to agree on list and definitions of categories o Observer agreement in practice: experienced independent observers should apply the same categories to a given sample of behaviour (working together but independently, or both analysing same film sequences): level of agreement gives a measure of reliability (see below) o The set of categories should be valid, i.e. they should map on to the real world and prove useful in theory and practise o Epistemological point: is ethology inductivist? Would Popper disapprove? Is the construction of an ethogram carving Nature at the joints? Or are categories low-level hypotheses? (Epistemology is the branch of philosophy which examines the basis of knowledge) Representative samples The array of episodes of behaviour one selects to observe and analyse should as far as possible be typical of that behaviour in that species or type of organism: watching hyenas only in the day would not give a full account of the hyena ethogram Informed estimates of overall frequency/probability of given behaviours can be computed if a record is kept of total observation time Within each observational episode the problem of representative sampling will also arise, and will be affected by the coding methods used e.g. continuous observation versus some kind of time-sampling (see below) Coding methods Coding is the application of category names to samples of behaviour of one or more organisms. This needs to be done to maximise accuracy which means that the codes are applied correctly (in terms of how they have been defined) to a representative sample of the behaviour Correctness is reflected in reliability (see below) If the richness or rush of behaviour is such that only some of the behaviour can be coded and some has to be left uncoded some kind of sampling will have to be used Sampling methods include continuous recording and various kinds of intermittent recording, often called time sampling. Continuous recording If this is practicable it is usually considered the richest and most accurate method of collecting observational data Behavioural categories may be grouped into one or more classes. Within any one class is a list of categories for behavioural states which are mutually exclusive and exhaustive (ME&E) Mutually exclusive means that only one state can occur at any one time: the organism cannot do more than one of them at once Exhaustive means that every possible action of the organism with regard to the class of behaviour is categorised: the organism must be doing one of the

4 categorised actions. To allow for new, previously unseen and thus uncategorised behavioural states one or more wild card miscellaneous categories may prove useful. A null category may also be useful to begin with before coding starts, or for periods during which the organism cannot be observed (e.g. it goes behind a bush, or you go behind a bush) For behavioural states which can occur simultaneously separate classes are required. Behavioural events (occurring at an instant in time with no recorded duration) may be added within or between behavioural classes Time sampling It may require less unremitting attention but permit acute observation only to apply categories intermittently, with attentional respite between codings One way is to use time sampling or instantaneous recording. Some kind of time-marker should be used to standardise such time sampling e.g. a new categorisation is made on the instant of every 30 th second. Successive points in time for coding should be close enough to pick up most or all changes in behaviour One-zero sampling Another method is to divide time into successive intervals, e.g. of 30 seconds, and for each interval record each category of behaviour which occurs at least once, or more than once, during that interval. This requires less concern than instantaneous recording about exactly how to code behaviour at a particular instance, but still allows the occurrence of behaviour in time to be approximately logged with more time to decide on which categories are applicable. With a coarse time scale either method of time sampling will introduce inaccuracies, loss of data (some unrecorded behaviours) in instantaneous sampling, and loss of order and of frequency information in one-zero sampling As the time scale becomes finer and finer the time sampling methods will approach more and more closely to continuous recording Multiple organisms to observe Depending on the questions being asked and other factors a routine rota circulating around the organisms of interest may be useful Concentrating on one focal organism for a sufficient period of continuous observation and then moving to the next may be the most fruitful and representative method to obtain rich data Interaction between organisms are likely to be important however, so that it may be useful to allocate an actor and a recipient to a particular category of action Reliability o Inter-observer reliability can and should be computed by having two or more experienced observers independently coding the same behaviour

5 conjointly (or using film) and then making a technical assessment of the degree of inter-observer agreement (e.g. using Cohen s kappa, which allows for the proportion of agreements likely to arise by chance alone). o Intra-observer reliability should also be measured (film very helpful here) to be on the lookout for: o shifts as a result of improvement with practice (early records may be discounted) o Drift in application of criteria as a function of fatigue or other factors (to be avoided in future, and contaminated records excluded) o Inability to achieve consistent results for whatever reason (don t use this person s data: hire someone else) o Poor reliability may result from poor categories, as well as from poor observers. Such categories should be revised, or scrapped. ANALYSIS OF NOMINAL DATA: to be expanded in workshop 1. Elementary statistics 2. Time-event logs 3. Reliability analyses 4. Sequential analyses 5. Analysis of temporal patterns