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image) but also in terms of experimental methodology, which upstream serves
analysis of the problem and downstream the validation of ideas. As previously
mentioned, see section 8.2.2, this relation between sound and interaction is an
emerging issue. It is dealt with, in particular, in the context of the European COST-
Action SID.
8.5.3.
Experimental approaches specific to interactivity
From an experimental point of view, the notion of interactivity can be deployed
on two different time scales:
- short term, linked the specific execution time of the task, which involves
chronometric type investigation methods; and
- more long term, linked to the global time of experience, which requires
alternative methods involving, in particular, some learning and even memorizing.
They are presented in succession in the rest of this section.
8.5.3.1.
“Chronometric” methods
In the interaction process, the so-called “chronometric” methods [LEM 09]
essentially measure the influence of sound in terms of reaction time (RT), movement
time and more globally the time it takes to carry out the task.
The measure of the RT, for example, can be relatively complex to carry out in so
far as this unit brings several aspects into play that come from theories of the signal
detection and the processing of information. Thus, according to Donders' model
[DON 69], the RT necessary to make a choice after an auditory stimulation
successively puts in play - in a cumulative way - the simple reaction time (including
the motor execution stage), discrimination time and choice time (see [SUE 07] for
more details on the subject).
In this context it is important to take into account the fact that the measure of
time it takes to carry out a given task must be able to be done at “iso-difficulty”, i.e.
by ensuring that the task of each experiment represents the same mental load for the
user as closely as possible (see section 8.5.4.2 for the definition of this notion).
8.5.3.2.
Alternative methods (learning, memorization, etc.)
When the level of human-machine interactivity is higher than for a simple
reaction to an auditory stimulus, it can be relevant to concern ourselves with
methods of alternative measures, taking into account more complex phenomena
linked to the time of manipulation of the system. This is the case, for example, with
