Individuals with autism spectrum disorder show normal responses to a fear potential startle paradigm.

Bernier et al. (2005) tested fear learning in teens and adults with autism. They used loud white-noise bursts paired with colored lights that signaled danger. Electrodes under the eye measured how hard the eye blinked. The team compared the startle size between people with ASD and matched peers without ASD.

Both groups blinked harder when the danger light was on. The size and speed of the blink did not differ between the ASD and typical groups. The result says the basic fear circuit, including the amygdala, works normally in autism on this task.

Mason et al. (2021) later repeated the same test in children and got the same null result. They added brain scans and showed that within ASD, kids with bigger amygdalas linked stronger blinks to higher anxiety. The story is extended, not overturned.

Kaufman et al. (2010) looked like a contradiction at first. They found kids with ASD blinked more to pleasant pictures, the reverse of typical. The key difference is picture type: Raphael used fear cues, S used happy and sad photos. Different triggers, different rules.

Castañe et al. (1993) is the grandparent study. It first reported normal startle modulation in ASD using simpler tones. Raphael swapped in fear cues and kept the null finding, building a 30-year line of replication.

If you hoped fear-potentiated startle would flag ASD, let it go. The measure is stable across age and labs. Instead, use the task to check anxiety within ASD: bigger blinks plus big amygdala point to worry, not diagnosis. Keep your behavior plans focused on skill building; the basic threat circuit does not need fixing.