1 MATERIALS YOU WILL BE ASKED TO DECIDE WHETHER THE REVIEWER WHO WRO...

4.1 Materials

you will be asked to decide whether the reviewer

who wrote the review recommended or did not

Sixteen customer-reviews were extracted from

recommend the reviewed product on a 1-5 scale:

Blitzer, Dredze, and Pereira’s sentiment data-

Number 5 indicates that the reviewer highly rec-

base (Blitzer et al., 2007). This database con-

ommended the product, while number 1 indicates

tains product-reviews taken from Amazon

¹

that the reviewer was unsatisfied with the prod-

where each review is rated by its author on a 1-

uct and did not recommend it.”

5 star scale. The database covers 4 product

In the second experiment, in addition to the

types (domains): Kitchen, Books, DVDs, and

psychological experiment, the latencies follow-

Electronics. Four reviews were selected from

ing reading of the texts up until the clicking of

each domain. Of the 16 extracted reviews, 8

the mouse, as well as the biometric measure-

were positive (4-5 star rating) and the other 8 –

ments of the mouse’s trajectories, were recorded.

negative (1-2 star rating).

In both experiments each subject was run in an

Given that in this experiment we examine the

individual session and had an unlimited time to

polarity of the last sentence relative to that of the

reflect and decide on the polarity of each text.

whole review or to a few other sentences, we

Five seconds after a decision was made (as to

focused on the first reviews (as listed in the

whether the reviewer was in favor of the product

aforementioned database) of at least 5 sentences

or not), the subject was presented with the next

or longer, rather than on too-short reviews. By

text. The texts were presented in random order so

“too-short” we refer to reviews in which such

as to prevent possible interactions between them.

comparison would be meaningless; for example,

In the initial design phase of the experiment

ones that range between 1-3 sentences will not

we discussed the idea of adding an “irrelevant”

allow to compare the last sentence with any of

option in addition to the 5-star scale of polarity.

the others.

This option was meant to be used for sentences

that carry no evaluation at all. Such an addition