Adjective that describes a person who shows a lot of enthusiasm in the beginning but gets bored gradually?

Can anyone provide a word which describes a person who shows a lot of enthusiasm in the beginning but gets bored gradually and eventually leaves the task uncompleted?

I looked at jaded, but it doesn't fulfill the criteria. Jaded seems to describe more of an overworked fellow, whereas the word I'm looking for would describe the nature of person. The word I'm looking for would describe a person who always exhibits this behavior.

The term distractible can be used to describe someone who is

subject to distraction

Distract is defined as

to draw the attention of (a person) away from something

However, these terms speak more to attention, rather than enthusiasm.

While not an adjective, you might consider dilettante

a dabbler or a person who cultivates an interest without really committing or learning anything in depth.

SUPPLEMENT:

On further thought, the term fickle may be useful

Characterized by erratic changeableness or instability, especially with regard to affections or attachments; capricious

A person who continuously and repeatedly expresses enthusiasm, confidence, and an almost excessive zeal at the start of any new task or adventure only to abandon it after a short time would appear to be hyperthymic

Hyperthymic people are those people who have so much energy, do so many things and get so much done they annoy others. Goel, Terman and Terman (2002) defined Hyperthymia as equivalent to Hypomania but without the impairment. So if you lose control it is hypomania and you get diagnosed with a mental illness (Bipolar.) But Hyperthymia by this definition means you are able to hold it together.

According to the limited number of experts in this field the following traits are also typical of a hyperthymic personlity:

• increased energy and productivity
• self-assurance, self-confidence
• strong will
• risk-taking/sensation seeking
• love of attention
• low threshold for boredom

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