The neural mechanisms involved in curiosity and uncertainty reduction

In the 60*s and 70*s, curiosity and exploration behavior in humans and
non-human animals were topics of intense investigation among experimental
psychologists. This research was guided by Berlyne (e.g., 1966), who conducted
many experiments on human curiosity and exploration, and developed an extensive
theory on this topic. Berlyne proposed that humans normally strive to maintain
a medium, optimal level of arousal. The induction of uncertainty, for example
by unexpected, ambiguous or conflict-inducing stimuli, leads to a rise in
arousal which is experienced as an aversive state (e.g., Berlyne, 1967).
Accordingly, when confronted with uncertainty-inducing stimuli people will tend
to explore these stimuli in order to reduce the uncertainty associated with
them (Nicki, 1970). According to Berlyne, the reduction of uncertainty through
access to relevant information is rewarding. He also proposed that prior
uncertainty facilitates the intake of information, which improves learning and
memory (Berlyne & Normore, 1972). The research by Berlyne and his colleagues
has led to some practical applications in education (MacLachlan, 1986) and
advertising (MacLachlan & Jalan, 1985). However, the topic has been largely
neglected in cognitive neuroscience for the last 30 years, and little is known
about the neural mechanisms involved.
Although no prior studies have investigated the neural mechanisms involved in
uncertainty and uncertainty reduction, a few recent neuroimaging studies have
investigated the brain activation associated with novelty (Wittmann, Bunzeck,
Dolan, & Düzel, 2007; Wittmann, Daw, Seymour, & Dolan, 2008). These studies
showed that novel stimuli enhance behavioral exploration, and that
novelty-based exploration activates brain areas involved in reward processing,
possibly mediated by the dopaminergic system. It is plausible that novelty is
used as a predictor of uncertainty, since these two aspects often coincide in
the natural world (Wittmann et al., 2008). If this is true, uncertainty
reduction is likely to activate brain areas involved in reward processing as
well.

The aim of the proposed study is to investigate the link between uncertainty
reduction and the reward system, as well as the link between uncertainty
induction and conflict, by means of an event-related fMRI study. We expect that
uncertainty will result in activation of brain areas associated with conflict,
such as the anterior cingulate cortex. In addition, we expect that uncertainty
reduction will result in activation of brain areas associated with reward, such
as the striatum, the orbitofrontal cortex and the amygdala. Finally, we predict
that stimuli that have initially been associated with uncertainty will be
memorized better than stimuli that have not been associated with uncertainty
(Berlyne & Normore, 1972).

We will use an adapted version of the paradigm used by Berlyne & Normore
(1972). On each trial, a sequence of two pictures of common objects is
presented. There will be four different trial types:
1. Blurred-Clear: a blurred picture followed by the corresponding clear picture.
2. Clear-Blurred: a clear picture followed by the corresponding blurred picture.
3. Clear-Clear: a clear picture followed by the same clear picture
4. Blurred-New Clear: a blurred picture followed by a different clear picture
Note that the blurred picture in trial types 1 and 4 will induce uncertainty
whereas the blurred picture in trial type 2 will not, since in trial type 2
participants already know what object is depicted (Berlyne and Borsa, 1968;
Berlyne & Normore, 1972). Similarly, the clear picture in trial type 1 will
cause uncertainty reduction whereas the clear picture in trial types 2, 3 and 4
will not.
There will be a jittered interval in between the first and the second picture
of each trial. The intertrial interval will be appropriately jittered, and the
average trial duration will be approximately 15 s. There will be 35 trials of
each condition. The 4 different trial types will be presented intermixed, in a
pseudorandom order.

The proposed study will consist of one experimental session within the MRI
scanner, followed by an unexpected free-recall test and the administration of
two curiosity questionnaires (the Perceptual Curiosity Scale and the Epistemic
Curiosity Questionnaire; Collins, Litman, & Spielberger, 2004; Litman, 2008)
outside the scanner. Total scanning time will constitute maximal 60 minutes.
The total duration of the experiment, including the free recall test and the
questionnaires, will be approximately 90 minutes.
Participants will watch pictures of common objects while fMRI data is acquired.
Each picture can be either ambiguous (i.e. a blurred object), or not ambiguous
(i.e., a clear object). Participants will be informed about the four possible
trial types, and will be asked to watch each picture carefully. We will tell
participants that the aim of the study is to assess the brain activation
related to seeing clear and blurred pictures. Every five minutes there will be
a short break in which the experimenter talks to the participant to make sure
the participant is still watching the pictures. After the scanning session,
participants will perform an unexpected free recall test outside the scanner,
in which they are asked to write down the names of as many objects as they
could recall from the pictures they have just seen. Following the free recall
test, participants will complete the two curiosity questionnaires. After this,
they will be debriefed about the purpose of the experiment and will be given
either a monetary reward or course credits.

Risks:
There are no risks associated with behavioral testing except the occasional
possibility of some boredom or fatigue. Testing will stop if a subject displays
frustration or appears tired.
There are no known risks associated with participating in an fMRI study. This
is a noninvasive technique involving no catheterizations or introduction of
exogenous tracers. Numerous human subjects have undergone magnetic resonance
studies without apparent harmful consequences. Radiofrequency power levels and
gradient switching times used in these studies are within the FDA approved
ranges. Some people become claustrophobic while inside the magnet and in these
cases the study will be terminated immediately at the subject's request. The
only absolute contraindications to MRI studies are the presence of intracranial
or intraocular metal, or a pacemaker. Relative contraindications include
pregnancy and claustrophobia. Subjects who may be pregnant, who may have
metallic foreign bodies in the eyes or head, or who have cardiac pacemakers
will be excluded because of potential contraindications of MRI in such
subjects.

Benefits: Although there is no direct benefit to the participants, the proposed
research is expected to make a significant contribution to our understanding of
the neural mechanisms underlying curiosity and uncertainty reduction. It will
also be informative about the effects of prior uncertainty on memory.
Ultimately, this can be beneficial for various practical purposes, including
the development of new teaching methods and marketing strategies. In terms of
scientific contribution, the study will be the first study to investigate the
neural basis of curiosity and uncertainty reduction.
The importance of the benefits gained from this research far outweighs the
minimal risks involved.