Blank expression

If someone has just been hit on the head and retains a blank or dazed expression, this can warn of concussions early.

[2] The term "poker face" is described as a deliberately induced blank expression meant to conceal one's emotions, referring to the common practice of maintaining one's composure when playing the card game poker.

[3][4] This term comes from the special language used in poker,[5] and is not only about a person's facial expression but also other extraneous movements that could give insight into what they are feeling, such as clenching fists, bouncing a leg, or constant repositioning of their body and or cards.

[7] Round games at cards, which reads "It follows that the possession of a good poker face is an advantage.

No one who has any pretensions to good play will betray the value of his hand by gesture, change of countenance, or any other symptom.