Affective modulation of the startle eyeblink and postauricular reflexes in autism spectrum disorder.

Kaufman et al. (2010) showed pictures that make most people feel happy, scared, or upset to two groups: kids with autism and kids without. While each child watched, the team zapped a tiny puff of air near the ear and filmed two small reflexes: the eye-blink and the tiny muscle behind the ear that pulls when we like something.

The goal was to see if the autism group’s body reacted the same way to emotional pictures.

The autism group did not follow the usual pattern. Their eye-blink got smaller, not bigger, to scary pictures. The little ear muscle jumped more to unpleasant scenes instead of pleasant ones. It was as if the first step of “feel” processing ran backward.

These reflex flips mean the brain’s fast emotion track works differently in autism.

Older startle papers said “nothing to see here.” Bernier et al. (2005) and Castañe et al. (1993) found normal fear-potentiated startle. The new study does not cancel those out; it just zooms in closer. Earlier work used simple loud sounds; S et al. added rich emotional pictures and a second reflex, letting subtler quirks show up.

Takahashi et al. (2017) later showed the basic startle size stays stable over a year, giving us confidence that the odd pattern is reliable, not noise.

Pan et al. (2025) widened the lens: preschoolers with autism also show flat heart-rate while missing social cues. Together the papers trace a line—early-stage emotion reactions can look “off” long before words enter.

If you use happy or calm faces to cue relaxation, check the child’s body, not just their words. A client might stare at a smile yet the ear muscle or blink says “threat.” Swap pictures, add extra pairing trials, or teach labeling of internal cues. Tiny reflexes give you instant, word-free feedback on whether your affective prompt is landing right.