Part of an ongoing series of 5e (2014) Rules notes.  See the end of the post for notes on 5.5e (2024) rules.

I’ve found Insight rules terribly underutilized in the D&D games I’ve been in. Wisdom (Insight) [PHB 178] is essentially Perception for personalities.

Your Wisdom (Insight) check decides whether you can determine the true intentions of a creature, such as when searching out a lie or predicting someone’s next move. Doing so involves gleaning clues from body language, speech habits, and changes in mannerisms.

Examples of using Insight

Bob the Tailor is a town elder, who’s fluttering around trying to keep the party from the abandoned mine outside the town. It would be useful to know where his fear is oriented — toward the party, toward the town, toward a third party, or toward himself? Is he lying when he talks about the mysterious music people have heard in the area? If we we say we’re going to the mine anyway, does his fear spike — or is it anger? Is his smile when he sees the constable walking this way the confidence of seeing an approaching ally, or a deceptive cover for terror at being discovered?

Insight can help with all that.

In other cases, you might use Insight to figure out if the guy you’re gambling with is confident in his hand. How does he feel about that last card he drew?  Is your date having a good time? Sure, she says she likes that roast beast you ordered for her … but how is she really feeling?

If someone’s trying to actively resist others using their Insight against them, they usually roll Charisma (Deception). (This is a case where one could easily use other base states for the Deception role, however — an academic using Intelligence (Deception) in hiding their bias in a paper, for example, or someone using Strength (Deception) to hide how incredibly freaking heavy that chest of gold they’re showing off with is.)

But rather than Active rolls, this is also a case where Passive skills come into play — the GM can consider passive Insight (or another’s passive Deception) to give give unsolicited clues about “He’s behaving a little twitchy,” or “He seems genuinely worried about you,” or even “You notice she seems attracted to the barkeep.”

Limitations of Insight

It does have limitations. It can indicate that someone is lying — but not necessarily what they are lying about,  or why they are lying, or what the truth is. People lie, after all, for a lot of reasons. Insight might tell you that the city guard you’re talking with still seems highly suspicious of you after your story … but it won’t tell you if he’s going to let his friends know to keep an eye out on you, or that he’s going to try to ambush you later on.

In short, Insight gives you, well, insight into underlying feeling, reactions, etc., but not necessarily why they are reacting that way. Is the guard at the door speaking a bit flatly when he tells you about how great a guy the grand vizier is? Yeah, you can pick that up with Insight, but it’s going to be more difficult (i.e., take more time and questions and other actions) to tell if the change because of some sort of loyalty spell, or from fear that the vizier’s secret police are monitoring him, or even just boredom with people pumping him for information about the vizier.

Tells

Some DMs just provide the “tells” the player is seeing, and lets them draw conclusions. “The guy definitely has sweat beading on his forehead.” “Her eyes keep shifting around the room, never quite meeting yours.” “His voice is definitely rising in pitch and intensity.” “She’s tugging at her ear, the same way she was during that card game last night when she had a winning hand.”  Things like that.

Of course, “things like that” are actually sort of Perception things — something that can just come out of the DM’s color text or description of the interaction.  Insight seems to blend both Perception and Investigation (what is there, and what does it mean) for social interactions. If all the DM gave me was vague physical tics, I’d probably ask for more of what that means to me (and not trust that I the Player understand such things the same way as the DM or module writer).

The nature of Insight — picking up on tells, physical and verbal expressions, etc. — also requires up front you have a way of perceiving and interpreting such things. Dealing with the human barkeep at the tavern is one thing. Trying to read the body language of a gelatinous cube is another.

Even in less extreme situations, Insight might be hampered by unfamiliarity with the target’s customs and culture: shouting and waving around your spear might be an expression of hostility by this never-before-met humanoid, or it might be a ritualized greeting, or a mating display. Insight might still work, but less reliably.

Remote use of Insight

Finally, Insight can be used without the target standing in front of you — picking out a great gift for your girlfriend (or for the prince) based on what they’ve enjoyed in the past, or figuring out how likely the savage Orcish war leader you keep encountering is to attack the city or respond to various counters. I’d probably use a normal Difficulty DC as the opposition, and familiarity (or lack thereof) with the target would be a key in determining how difficult the estimate was.

Overusing Insight

Because it deals with interpersonal relationships, Insight can be easily abused or overused. Overuse of  Insight is a bit like overuse of Perception (“I evaluate every person in the bar” is like “I search every room thoroughly”); it’s doable, but should carry some costs (time being a major one, but also something like the likelihood someone is going to catch you staring at them — or their love interest — and take offense).

Overuse also takes away a bit from Role Playing. The DM should be able to use passives to feed needed clues to the players about how people are behaving without their insisting on active Insight rolls, just as they feed visual prompts in the normal course of things rather than  players requiring active Perception  roles as they walk through town.

Who rolls Insight?

Note: Insight is one of those skills (like Perception, etc.) where sometimes it makes more sense for for the DM to roll it for a character, to determine if you can figure out something, can’t figure out something, or are deceived in your insight about something.

I would suggest as well that, like Perception, Insight can be abused by having everyone gang up about it. “Well, Sue, you can try using Insight to tell whether the merchant is ripping you off.” “Okay, I’ll try that.” “Me, too!” “Rolling Insight.” “Wait, let me do it, too!”

Aside from the fact that everyone rolling Insight means it’s likely someone is going to hit the DC, it’s also unrealistic. Insight depends on observation, focus, and over some period of time. While it’s often invoked mid-encounter (“Is the barkeep being truthful about when the wizard left?”), in most cases it should take some time — some questions, some comments, some jokes, some interpersonal communications to baseline the subject’s reaction.  Having a party of 8 trying to do that to one target is unlikely (or suspicious). Aside from the person doing the actual talking, everyone else probably has something else to keep their attention (the guards, that guy in the corner, the gems in the idol, that meal last night, etc.).

Which is still more reason to let the DM do the rolling behind the screen. “Sue, you’re pretty sure he’s marking up the price outrageously, even though you don’t know him that well. Jeff, you think the merchant’s honest, but, to be fair, you were just talking with Mary about what supplies the group needs. Bob, you’ve been shopping for those potions you wanted, so I don’t think you’ve had a chance to figure out anything about how this guy ticks.” At the very least, the likely engagement of individual characters and the time they invest should go into the DC they have to beat with their Insight roll.

Do you want to know more?

Insight 5e: How to Use It Right in DnD (And Better!) – Awesome Dice

Any changes in 5.5e?

Are there changes in how Insight works in 5.5e (2024), rather than 5e?

Actually, for all that 5.5e zeroes in on social interactions (asserting Influence as its own Action, for example), Insight gets very little love, only showing up in the PHB in the 5.5e Skills list, which says only:

Discern a person’s mood and intentions.

Okay, it also shows up in the Search [Action] Vocabulary, where it’s sub-task in such actions is “Thing to Detect: Creature’s state of mind.”

I don’t find any other reference to it in the PHB or in the DMG.

It’s strange to have less information than the previous edition. Weird.

If anyone finds something more, please let me know.