A logo is the introduction, and the sign-off. Nothing more than familiarity, thereafter.

It is the epistemological value most associated with a brand, and how the person has experienced the idea, product or service (ips) of a brand. I consider it to be the single-minded key thought an individual has about an ips. This is not the single-minded key thought an advertiser broadcasts to them, but the one they have after they've experienced the ips, for themselves. It's how a person sums up this experience in their mind, how they recall it, and how they gauge it against other experiences. This is what it eventually becomes.

I'll add, like all introductions: A logo should be clear, terse, unique and respect the prospect or its own content. And like a good sign-off, know when it's time to go, and how to do it in a memorable way, without offending. If you're lucky, you're a company that teaches and informs, with selling only as an extension thereafter. In this case, a logo can take on emergent qualities that begin to resemble metaphors for people. It's at this stage that someone tries to infer or inject these metaphors into the logo. In my experience, this is a bad idea.

Logos are often tasked with to much information in an effort to say everything a company thinks, does, or feels, but we know that's not how we make introductions to people in casual or candid settings. Someone notices us, we make eye contact, we've got 1 or 2 key things of note to say, and then we listen (or vice versa). A good logo is an identifier first and foremost. At best/worse, it's a contrast to what may already be out there.

Having said this, and in an attempt to make this a cohesive thought: The impact of a logo is relative to the context it's experienced in.