Ubuntu – How to record from the microphone input

I have an audio input plugged into my mic jack. In alsamixer, when I unmute and amplify the mic input, I can hear this audio out of my speakers. However, running arecord -d 5 foo.wav and aplay foo.wav results in an empty file; the same when recording through audacity – empty.

Why does this happen? How do I record this input?

arecord -L produces the following, if this is helpful:

default
    Playback/recording through the PulseAudio sound server
pulse
    Playback/recording through the PulseAudio sound server
front:CARD=nForce2,DEV=0
    NVidia nForce2, NVidia nForce2
    Front speakers
surround40:CARD=nForce2,DEV=0
    NVidia nForce2, NVidia nForce2
    4.0 Surround output to Front and Rear speakers
surround41:CARD=nForce2,DEV=0
    NVidia nForce2, NVidia nForce2
    4.1 Surround output to Front, Rear and Subwoofer speakers
surround50:CARD=nForce2,DEV=0
    NVidia nForce2, NVidia nForce2
    5.0 Surround output to Front, Center and Rear speakers
surround51:CARD=nForce2,DEV=0
    NVidia nForce2, NVidia nForce2
    5.1 Surround output to Front, Center, Rear and Subwoofer speakers
surround71:CARD=nForce2,DEV=0
    NVidia nForce2, NVidia nForce2
    7.1 Surround output to Front, Center, Side, Rear and Woofer speakers
dmix:CARD=nForce2,DEV=0
    NVidia nForce2, NVidia nForce2
    Direct sample mixing device
dmix:CARD=nForce2,DEV=1
    NVidia nForce2, NVidia nForce2 - MIC ADC
    Direct sample mixing device
dsnoop:CARD=nForce2,DEV=0
    NVidia nForce2, NVidia nForce2
    Direct sample snooping device
dsnoop:CARD=nForce2,DEV=1
    NVidia nForce2, NVidia nForce2 - MIC ADC
    Direct sample snooping device
hw:CARD=nForce2,DEV=0
    NVidia nForce2, NVidia nForce2
    Direct hardware device without any conversions
hw:CARD=nForce2,DEV=1
    NVidia nForce2, NVidia nForce2 - MIC ADC
    Direct hardware device without any conversions
plughw:CARD=nForce2,DEV=0
    NVidia nForce2, NVidia nForce2
    Hardware device with all software conversions
plughw:CARD=nForce2,DEV=1
    NVidia nForce2, NVidia nForce2 - MIC ADC
    Hardware device with all software conversions

Changes made on the Input tab of the System Settings -> Sound dialog make no difference at all. No sound comes out of my speakers because of them, and Audacity records nothing as a result of changing any setting (either the connector or the input volume). There is only one "device for sound input" – the Internal Audio Analog Stereo.

Oddly, in Audacity, changing the recording source (say from default:Line:0 to default:Mic:0, or even Mono to Stereo) sets the mute checkbox on the aforementioned dialog.