clinical

dispassionate, objective

impersonal, professional

businesslike

apathetic, hard, indifferent, unconcerned

disinterested, incurious, uninterested

misanthropic

aloof, antisocial, asocial, buttoned-up, cold, cold-eyed, cool, detached, distant, dry, frosty, offish, remote, standoff, standoffish, unbending, unclubbable, unsociable

antiseptic, arctic, brittle, chill, chilly, clammy, cold-blooded, coldish, frigid, frozen, gelid, glacial, hard-eyed, icy, uncordial, unfriendly, unsympathetic, wintry (also wintery)

reticent, silent, taciturn, uncommunicative

reserved, soulless, undemonstrative, unemotional, unresponsive

bloodless, coldhearted, hard-hearted, heartless, kindless, pitiless, uncaring, unfeeling

earnest, grave, humorless, no-nonsense, po-faced [British], sedate, serious, severe, sober, sobersided, solemn, staid, uncomic, unsmiling, weighty

dignified, distinguished, elevated, serious-minded