Word for stating "negative influence on other opinions"

What is the word for influencing others' decisions and opinions in a negative way?

In other words, what is the best choice to fill the blank in the following example:

To avoid -----, the comments are not visible for the participants until the end of the session.

From Oxford living Dictionaries

Prejudice
VERB

[WITH OBJECT] Give rise to prejudice in (someone); make biased:

‘the statement might prejudice the jury’

More example sentences from OLD

‘The smell of antiseptic and the fear of injections prejudiced me against him then, but he was the most important person in our village.’

‘There are very many legal things I can think of that would prejudice me against a person more than smoking.’

Your sentence:

To avoid prejudicing the participants, the comments will not be visible until the end of the session.

Synonyms: bias, influence, sway, predispose, make biased, make partial, make partisan, colour, poison, jaundice, warp, twist, slant, distort

How about bias?

OD:

bias: a systematic distortion of a statistical result due to a factor not allowed for in its derivation

Your example:

To avoid bias, the comments are not visible for the participants until the end of the session.

Making comments available ahead of time has the potential to distort the views of the participants when what you want is their own personal unbiased feedback.

You may be looking for manipulation - (negatively) influencing opinions to serve one's own (often selfish) interests.

To avoid manipulation (of individual opinions), the comments are not visible for the participants until the end of the session.

M-W:

manipulate verb
3 : to change by artful or unfair means so as to serve one's purpose

The editorial was a blatant attempt to manipulate public opinion.

mental contamination

Contamination: The act or process of contaminating; pollution; defilement; taint; also, that which contaminates; The process of making a material or surface unclean or unsuited for its intended purpose, usually by the addition or attachment of undesirable foreign substances.

[Wiktionary]