Photoreception in marine animals
After earning a Harvard doctorate in 1917, Hecht developed experiments on light responses in ascidians and clams. Their relatively slow responses allowed comparisons of light intensity, temperature and reaction time. He sought measurable chemical explanations of photoreception rather than simply recording whether animals contracted or avoided light.
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Photochemical models and dark adaptation
Hecht used the breakdown of photosensitive pigment in light and its restoration in darkness as a model for adaptation. He extended approaches developed with invertebrates to human vision and directly investigated the bleaching of rhodopsin in solution.
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Incident photons and absorbed light
In 1942 Hecht and colleagues related the threshold for detecting a weak flash to small numbers of photons. They distinguished light arriving at the eye from light actually absorbed by rod pigments, estimating only a handful to about a dozen absorbed photons near threshold. This supported single-photon sensitivity in individual rods, rather than reliable perception of every single photon by a person.
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Instruments and the Columbia laboratory
From 1926 Hecht developed a research group at Columbia. With Simon Shlaer he produced instruments for dark-adaptation measurements and studied brightness discrimination, flicker, color vision and night vision. Students including George Wald went on to investigate the chemical mechanisms of visual pigments.
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