). THUS, THE MOST FREQUENT EVALUATION OF OF A SENTENCE WITHIN A T...

1962)). Thus, the most frequent evaluation of

of a sentence within a text with its degree of in-

the product (which is the most uninformative

formativeness.

one) also should surface at the end of the text

due to the ease of its retrieval, which is pre-

Giora (Giora, 1985, Giora, 1988) defined a

sumably what product review readers would re-

discourse topic (DT) as the least informative

fer to as “the bottom line”.

(most uninformative) yet dominant proposition

To the best of our knowledge, this psycholin-

of a text. The DT best represents the redun-

guistic prediction has not been supported by psy-

dancy structure of the text. As such, this propo-

cholinguistic evidence to date. However, it has

sition functions as a reference point for process-

been somewhat supported by the computational

ing the rest of the propositions. The text posi-

tion which best benefits such processing is text

results of Yang, Lin and Chen (Yang et al.,

initial; it facilitates processing of oncoming

2007a, Yang et al., 2007b) who classified emo-

propositions (with respect to the DT) relative to

tions of posts in blog corpora. Yang, Lin & Chen

when the DT is placed in text final position.

realized that bloggers tend to emphasize their

feelings by using emoticons (such as: ☺," and

Furthermore, Giora and Lee showed (Giora

#) and that these emoticons frequently appear in

and Lee, 1996) that when the DT appears also

at the end of a text it is somewhat information-

final sentences. Thus, they first focused on the

ally redundant. However, functionally, it plays a

last sentence of posts as representing the polarity

role in wrapping the text up and marking its

of the entire posts. Then, they divided the posi-

tive category into 2 sub-categories - happy and

boundary. Authors often make reference to the

DT at the end of a text in order to summarize

joy, and the negative category - into angry and

sad. They showed that extracting polarity and

and deliberately recapitulate what has been

consequently sentiments from last sentences out-

written up to that point while also signaling the

performs all other computational strategies.

end of discourse topic segment.

4 Method

3 Polarity-classification vs. Topic-

extraction

We aim to show that the last sentence of a cus-

tomer review is a better predictor for the polarity

When dealing with polarity-classification (as

of the whole review than any other sentence (as-

with topic-extraction), one should again identify

suming that the first sentence is devoted to pre-

the most uninformative yet dominant proposi-

senting the product or service). To test our pre-

tion of the text. However, given the cognitive

diction, we ran two experiments and compared

prominence of discourse final position in terms

their results. In the first experiment we exam-

of memorability, known as “recency effect” (see

ined the readers’ rating of the polarity of reviews

below and see also (Giora, 1988)), we predict

in their entirety, while in the second experiment

that when it comes to polarity-classification, the

we examined the readers’ rating of the same re-

last proposition of a given text should be of

views based on reading single sentences ex-

greater importance than the first one (contrary

tracted from these reviews: the last sentence or

to topic-extraction).

the second one. The second sentence could have

Based on preliminary investigations, we sug-

been replaced by any other sentence, but the first

gest that the DT of any customer review is the

one, as our preliminary investigations clearly

customer’s evaluation, whether negative or

show that the first sentence is in many cases de-

positive, of a product that s/he has purchased or

voted to presenting the product or service dis-

a service s/he has used, rather than the details of

cussed and does not contain any polarity con-

the specific product or service. The message

tent. For example: "I read Isaac’s storm, by Erik

that customer reviews try to get across is, there-

Larson, around 1998. Recently I had occasion to

fore, of evaluative nature. To best communicate

thumb through it again which has prompted this

this affect, the DT should appear at the end of

review…..All in all a most interesting and re-

the review (instead of the beginning of the re-

warding book, one that I would recommend

view) as a means of recapitulating the point of

highly.” (Gerald T. Westbrook, “GTW”)

the message, thereby guaranteeing that it is fully

understood by the readership.