In simplest terms a dual-choice olfactometer is a piece of experimental equipment which allows the testing of the apparent preference of one odour against another, as shown by the organism “choosing” which smell to approach. This choice is assessed by observation of the behaviour of the organism within a choice arena or chamber.
It therefore needs to be an enclosed space where organisms can be presented with a choice between two odours. These odours may be two different added odours (variables), or there may only be one odour added which is tested alongside a control where no odour variable is offered. By carefully designing a strategy of testing the variables against a control, and also against each other, it is possible to develop a data set which indicates which variables are most preferred by the organism.
Dual-choice olfactometers are designed to minimise the possibility of other factors influencing the observed behaviour. If behaviour is being influenced by other factors then little confidence can be placed in the experimental outcome. For example, if the organism can see the source of the odour it may prefer the sight of the source, so this would no longer be a test of olfactory driven behaviour. Similarly, if the air flow through the variable delivery system is unbalanced then the organism may prefer the higher or lower air flow and make its choice based upon this mechanism. Special attention is therefore needed to “design out” these potential confounding variables, and “dry-runs” where no variables are loaded will help to spot any bias in the system which can be remediated.
So far I have only referred to “the organism”. This is because we can, in principle, make this type of choice arena for any organism that has a sense of smell and can display a behavioural response which indicates preference, where one exists. Humans regularly take part in odour preference studies, particularly in areas such as perfume development, although we are able to communicate preference in more ‘intelligent’ ways than just pointing at or moving towards the favoured smell.
Adult female mosquito
Obviously, for this project the organisms being studied will be adult mosquitoes, which have a history of being involved in olfactometer studies. In the next blog, I will look at some of the designs that have been used previously, and discuss the results of a design workshop that took place a few weeks ago.
Thanks for reading, and please ask questions or leave a comment below.
As a lay person I find what you are proposing does not seem random enough. For instance, temperature variance and humidity. I know that Dr Priestman studied mosquitoes in Africa, no doubt she has a fund of knowledge on this topic. Perhaps, to be truly inclusive, she should be the prime source of acknowledgement for your approach?
I think that when writing about technical matters it invariably pays to write in a technical authorship mode with headings, sub-headings, bullet points, etc. The item purports to be a technical discourse with much minutia and yet is told as a narrative tale which means that depending on the way that I read it I may or may not find salient points or interpret those items that you believe to be particular.
-oo0oo-
Introduction
A bit about you and your environment always helps to to form a mental image for the participants like me who will deduce from your style how you prefer to be dealt with, whether crushingly serious and matter of fact or approachable and relaxed. Your environment may induce other to suggest alternatives sites at which to find your bug or lead to a collegiate approach, someone may know someone else in a similar field whom from the details gleaned, they think you may get on with or, in fact, learn something.
Table of contents with brief descriptions
1. Olfactorometer
1.1 Summary
An olfactometer is…see Figure A.1.
1.2 The purpose of this experimentation is to…
2. Ochlerotatus punctor, Mosquito
Ochlerotatus punctor is a …see Figure B.1…see Figure B2…etc
2.1 Source of study material
3. Personnel involved in study
Round-up or early meetings…etc
3.1 How to contribute
4. Graphs and statistics
4.1…
4.1.1….
4.2 The helpful effects of quinine as in Gin and tonic.
Appendix elucidation of terminology
Index
Acknowledgements
-oo0oo-
Me, I used to be a technical author and wannabee writer. I have very little scholastic accreditation and am only included here because I am a social friend of Dr Priestman.
I wish you luck with your experimentation. If you want to disseminate your findings, and if you wish to gain information and/or support, I think that there is no other way of venturing to achieve such without being concise in your writing and taking your undoubtedly pleasant character out of the presentation.
People have not the time to meander through nice, inclusive chat and, as I intimated, having the narrative discourse can lead to word blindness, misinterpretation and even totally missing the nub of your treatise!
Ta-ta
Malcolm
Malcolm,
Many thanks for your comments and sorry for the slow reply.
I’d like to address some of your points head on, and a couple of the others slightly less directly by outlining why I have chosen to write the blog in the style that I have.
Firstly, when considering the lack of randomness in the experiment it is important to understand that this is a deliberate part of the experimental design. The design strives to control all of the variables which may influence mosquito behaviour when the mosquitoes are introduced to the olfactometer. If this is successfully done, and with enough repetition of the experiment to be statistically robust, then we can accept that the exhibited behaviour is, or is not, being changed by the variable of interest when presented within a certain set of conditions. Whether the behaviour would differ if the temperature or humidity was altered would require another set of repetitions, testing the previous outcome(s) under new conditions.
This has obvious limitations when trying to compare the laboratory findings to mosquito behaviour in a natural setting, where all the variables such as temperature and humidity will fluctuate. Unfortunately, there is no simple or quick way to be sure of the relative influence of the various variables in a holistic manner. There are various statistical treatments that can be put to work on this type of situation in nature, but recording all the necessary variables can be practically impossible, particularly aspects such as the age of the mosquitoes, whether they have mated or fed before.
On the subject of the writing style which I am currently using on this blog: This is section of my reply which has caused me to delay my response, as it is the area where I am least confident. Thus far it has used quite a personal, narrative style, which I do quite like writing in. I want to try and hold a balance between technical discussion and keeping the language and tone welcoming enough for general browsing, and to try and encourage interaction from the reader. I don’t want people to feel that they might have a question that might been seen as ‘beneath’ the subject matter – if anyone has a question or suggestion connected to the general topic area I want them to feel that they can ask it.
There is definitely a time a place for strictly technical discussion of the olfactometer and its use in experiments; where articles are being written for submission to scientific journals for example there is a generally accepted format and certain data are expected to be clearly and concisely displayed.
I do agree though that my style on this blog might lack clarity, and that this situation may become more obvious as the number of posts increase over time. I think I may be able to combine the 2 disparate approaches somewhat; perhaps by building a framework around the blog posts similar to the table of contents you suggest will allow the reader to understand the context of specific blog posts, without needing lengthy exposition.
I know I have not addressed all of your comments, but, for brevity, I have focussed on the two which were most thought provoking.
Thanks,
Rich
Hello, I read your blogs daily. Your humoristic style is awesome, keep uup the good work!