Transportation to Work. At Step 4, test is whether claimant has ability to return to past relevant work performed at substantial gainful activity level. Past insubstantial activity cannot demonstrate an ability to perform SGA. Available at DLC. Deference owed to ALJ’s credibility determination, but Appeals Council can overturn ALJ credibility determination if not supported by substantial evidence. Remand. Eligibility for Disabled Adult Child benefits requires that disability began before age 22 and continued until 6 months prior to application for benefits. Past insubstantial work cannot demonstrate an ability to perform SGA. Secretary's conclusion that claimant with schizophrenia is not disabled is not supported by substantial evidence. Claimant's ability to travel is "weak evidence" of a capacity to work, especially in light of repeated hospitalizations. The conclusions of two doctors that claimant can work are not persuasive, when the doctors' analysis consist of "four checkmarks on a standard form with an additional line or two of 'comments' at the bottom."