In an autistic mind, unwelcome stimuli quickly builds up, becomes painful, and eventually unbearable. If left unchecked, a Sensory Meltdown results. The “accumulation of painful stimulus” is akin to the build-up in a nuclear reactor, where dangerous levels of pressure have been exceeded, eventually leading to – BOOM! – an emotional explosion.
Hearing his father say “no” when he pointed to a bag of crisps, ended up being “the spark that ignited the flame”.