Question

As scientists psychologists have confidence in theories that

Answer 1

Psychologists place all their confidence in theories that are linked to evidence that they can see, are tied to observable evidence. This means that they stray further away from theories and more towards things that can be viewed and seen in order to validate their truth.

Answer 2

the answer is tied to observable evidence
Theories that tied to observable evidence had a solid measurement to be tested in order to prove whether those theories are right or wrong.
Without observable evidence, it would be closer to say that those scientific 'theories' are just personal opinion.