When under the effects of the Polymorph spell:

The target's game statistics, including mental ability scores, are replaced by the statistics of the chosen beast. It retains its alignment and personality.

If someone is polymorphed into a creature like a spider (INT = 1), a riding horse (INT + 2), or a cat (INT = 3), their intelligence is severely reduced. Does this impair their general ability to communicate with people?

Polymorph does prohibit speech:

The creature is limited in the actions it can perform by the nature of its new form, and it can't speak, cast spells, or take any other action that requires hands or speech.

However, this could be interpreted as only preventing the physical act of talking. If so, then one could still attempt to communicate with the polymorphed person by other methods such as telepathy.

Would telepathy allow someone to have a normal conversation with the polymorphed person, or would that person's severely impaired intelligence also impair their ability to communicate in general?

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