“The channel factor principle, thus, is one key to understanding why some situational factors have bigger effects than might be anticipated and why some have smaller effects. Seemingly big interventions and campaigns that provide no effective input channel in the form of situational pressures, or no effective behavioral outlet channel in the form of clear intentions or plans, will generally produce disappointingly small effects. And seemingly small situational factors that operate on important input or output channels will often exert gratifyingly large effects.”