function[sessions] = findAllfiles(obj, folder)
    
    cd(folder);
    files = dir;
    i=1;
    sessions = PDSession(''); % create empty session
    for s =1:length(files)
        if (strcmp(files(s).name, '.') || strcmp(files(s).name, '..'))
            continue;
        end
        
        if files(s).isdir            
            new_sessions = obj.findAllfiles([folder filesep files(s).name]);
            for i = 1:length(new_sessions)
                if ((length(sessions) ==1) && isempty(sessions(1).datafile))
                    sessions(length(sessions)) = new_sessions(i);
                else
                    sessions(i + length(sessions)) = new_sessions(i);
                end
            end
        else
            [base file ext] = fileparts(files(s).name);
            
            if strcmp(lower(ext), '.asc') 
                display(sprintf('\tFile found for Subject: %s', file));                
                if ((length(sessions) ==1) && isempty(sessions(1).datafile))
                    sessions(1) = PDSession([folder filesep files(s).name]);
                else
                    sessions(end+1) = PDSession([folder filesep files(s).name]);
                end
                i=i+1;
            end
            
            if strcmp(lower(ext), '.gazedata') 
                display(sprintf('\tFile found for Subject: %s', file));                
                if ((length(sessions) ==1) && isempty(sessions(1).datafile))
                    sessions(1) = PDSession([folder filesep files(s).name]);
                else
                    sessions(end+1) = PDSession([folder filesep files(s).name]);
                end
                i=i+1;
            end

        end        
    end
    %% do not return empty objects
    
    if ((length(sessions) ==1) && isempty(sessions(1).datafile))
        sessions = [];
    end