That which perceives feels thinks or intends

Discussion of the multiple meanings of'subject' could occupy a lengthy monograph, covering subjects from philosophy and linguistics, via the exact and the natural sciences, to politics and law. The few selected definitions provided above are the most relevant to memory research. We could benefit substantially from paying "attention to those implications of'subject' that tend to be overlooked in the design and analysis of experiments. 'Subject' originates from Latin, where it had originally meant 'to throw or place beneath'. Accordingly, experimenters frequently think that having thrown the subject into the experimental situation (definition 1) ensures control over that subject (definition 2). The truth is that to some degree or another, every subject, especially if unanaesthetized, is an entity that perceives, feels, thinks, etc. (definition 3). An experimenter must be tuned to these attributes, otherwise real embarrassments may ensue.

Although the subject is at the focus of the experiment, frequently the attention devoted to it by the experimenter is surprisingly minimal, even less than that allotted to the computer on which the paper reporting the experiment is later being written. It is not an outraging exaggeration to claim that in some subdisciplines in experimental neuroscience, except possibly those that deal with human subjects (*Homo sapiens), many investigators are unaware of the spectrum of attributes of their subject. This is a mistake that may result in "artefacts. So here are some elementary truths about the subjects of memory experiments, which some investigators tend to ignore, yet you couldn't afford doing so.

1. The subject has a history. It is never the featureless, utterly inexperienced mind that you might wished it were (definitely not a tabula rasa, Locke 1690). The appreciation that the subject's life did not start with your experiment (though, unfortunately, it may end with it), is a must for the proper design, "performance, analysis and interpretation of behavioural and physiological experiments (e.g. "priming, "state-dependent learning, "transfer).

2. Individual subjects of the same species differ from each other. (That individuals from different species are different should be obvious, although sometimes people tend to confuse species traits, expecting a "mouse to behave like a "rat, for example, in a problem box). This also applies to some degree to subjects that share the same genes ("neurogenetics), and moreover, even to subjects raised in the same environment—although, of course, the variability is smaller then in a genetically heterogeneous population in an heterogeneous environment (animals kept in different cages, humans raised in different cultures).

3. Miniature brains do not necessarily have miniature minds. A "honeybee can outperform the smartest of the elephants in some species-specific tasks. And miniature subjects are not homogeneous 'atoms of behaviour'. Surely, complex species are expected to display more behavioural variability than "simple ones, and we should in no way jump to "anthropomorphism. A powerful tool for smoothening behavioural and physiological 'noise' is statistics (Fisher 1966; Martin and Bateson 1993; Kerlinger and Lee 2000). Yet smoothening the noise must be distinguished from neglecting important differences among individuals. Such differences are important, because they may provide clues to potential breakthroughs (Benzer 1967). Statistics is important, attentive observation is even more so. It is useful to keep in mind the following citation from Martin and Bateson's (1993): 'Our general advice is not to become obsessed by statistical techniques, nor too cavalier in their use. Statistical analysis is merely a tool to help answer questions, and should be the servant rather than the master of science.'

4. "Reduced, "simplified preparations (such as isolated "Aplysia ganglia, "hippocampal slices, cell cultures, identified "synapses), the subjects of "reductive research programmes and experiments, do have a history as well. This history modifies the state and the response of the preparation (e.g. Frey and Morris 1997; Dudai and Morris 2000).

5. The subject's behaviour is always more complex than reflected in the data that you collect. This may be due to the fact that you have "a priori decided to choose only a selected parameter to study. Even Pavlov did it, and it was a key to his success: his dogs did a lot more than merely salivate in response to the metronome; Pavlov nevertheless decided to concentrate only on an easily quantifiable part of the conditioned reflex (Pavlov 1927). Another possibility is that you are not aware of the full spectrum of your subject's behaviour, because of lack of familiarity with the "system.

6. The subject has its own idiosyncratic understanding and appreciation of the experimental situation. Furthermore, questions that appear simple and intriguing to you may be of no interest whatsoever to the subject (e.g. "Drosophila pay attention to odours, students to music; most species will pay much attention to their own visceral sensations following the ingestion of food, surely more than following visual or auditory experience; "conditioned taste aversion). You must hence know which questions to ask and how to pose them, in order to satisfy the curiosity and boost the motivation of the subject to take part in the game (e.g. Pavlov 1927; Benzer 1967; Garcia et al. 1968).

7. The subject may trick you by doing what you wish it to do, by noticing your behaviour ('demand characteristics'; Orne 1962, see "bias; "Clever Hans). The subject may also be influenced by the behaviour of other subjects without you ever being aware of it ("observational learning).

8. Know thy subject. Pay special attention to it if you switch a species, a preparation or an "assay. Different species have different perceptions of the world and behave accordingly. An innate response pattern ("a priori) may be mistakenly taken by you as evidence for learning (e.g. Moore and Stuttard 1979; Wolfer et al. 1998; "artefact).

9. And last, but not least: beware of falling in love with your experimental subject, especially if it is only a fly (Dethier 1962). It will surely bias you, and may even become painful.

Selected associations: Anthropomorphism, Drosophila,

Homo sapiens, Model

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